media/media/src/main/java/androidx/media/MediaBrowserServiceCompat.java - platform/frameworks/support - Git at Google

 /*
  * Copyright 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package androidx.media;

 import static androidx.annotation.RestrictTo.Scope.LIBRARY;
 import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_ADD_SUBSCRIPTION;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_CONNECT;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_DISCONNECT;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_GET_MEDIA_ITEM;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_REGISTER_CALLBACK_MESSENGER;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_REMOVE_SUBSCRIPTION;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_SEARCH;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_SEND_CUSTOM_ACTION;
 import static androidx.media.MediaBrowserProtocol.CLIENT_MSG_UNREGISTER_CALLBACK_MESSENGER;
 import static androidx.media.MediaBrowserProtocol.DATA_CALLBACK_TOKEN;
 import static androidx.media.MediaBrowserProtocol.DATA_CALLING_PID;
 import static androidx.media.MediaBrowserProtocol.DATA_CALLING_UID;
 import static androidx.media.MediaBrowserProtocol.DATA_CUSTOM_ACTION;
 import static androidx.media.MediaBrowserProtocol.DATA_CUSTOM_ACTION_EXTRAS;
 import static androidx.media.MediaBrowserProtocol.DATA_MEDIA_ITEM_ID;
 import static androidx.media.MediaBrowserProtocol.DATA_MEDIA_ITEM_LIST;
 import static androidx.media.MediaBrowserProtocol.DATA_MEDIA_SESSION_TOKEN;
 import static androidx.media.MediaBrowserProtocol.DATA_NOTIFY_CHILDREN_CHANGED_OPTIONS;
 import static androidx.media.MediaBrowserProtocol.DATA_OPTIONS;
 import static androidx.media.MediaBrowserProtocol.DATA_PACKAGE_NAME;
 import static androidx.media.MediaBrowserProtocol.DATA_RESULT_RECEIVER;
 import static androidx.media.MediaBrowserProtocol.DATA_ROOT_HINTS;
 import static androidx.media.MediaBrowserProtocol.DATA_SEARCH_EXTRAS;
 import static androidx.media.MediaBrowserProtocol.DATA_SEARCH_QUERY;
 import static androidx.media.MediaBrowserProtocol.EXTRA_CALLING_PID;
 import static androidx.media.MediaBrowserProtocol.EXTRA_CLIENT_VERSION;
 import static androidx.media.MediaBrowserProtocol.EXTRA_MESSENGER_BINDER;
 import static androidx.media.MediaBrowserProtocol.EXTRA_SERVICE_VERSION;
 import static androidx.media.MediaBrowserProtocol.EXTRA_SESSION_BINDER;
 import static androidx.media.MediaBrowserProtocol.SERVICE_MSG_ON_CONNECT;
 import static androidx.media.MediaBrowserProtocol.SERVICE_MSG_ON_CONNECT_FAILED;
 import static androidx.media.MediaBrowserProtocol.SERVICE_MSG_ON_LOAD_CHILDREN;
 import static androidx.media.MediaBrowserProtocol.SERVICE_VERSION_CURRENT;
 import static androidx.media.MediaSessionManager.RemoteUserInfo.LEGACY_CONTROLLER;
 import static androidx.media.MediaSessionManager.RemoteUserInfo.UNKNOWN_PID;
 import static androidx.media.MediaSessionManager.RemoteUserInfo.UNKNOWN_UID;

 import android.app.Service;
 import android.content.Context;
 import android.content.Intent;
 import android.content.pm.PackageManager;
 import android.media.browse.MediaBrowser;
 import android.media.session.MediaSession;
 import android.os.Binder;
 import android.os.Build;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.IBinder;
 import android.os.Message;
 import android.os.Messenger;
 import android.os.Parcel;
 import android.os.RemoteException;
 import android.service.media.MediaBrowserService;
 import android.support.v4.media.MediaBrowserCompat;
 import android.support.v4.media.session.IMediaSession;
 import android.support.v4.media.session.MediaSessionCompat;
 import android.support.v4.os.ResultReceiver;
 import android.text.TextUtils;
 import android.util.Log;

 import androidx.annotation.CallSuper;
 import androidx.annotation.IntDef;
 import androidx.annotation.MainThread;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.annotation.RestrictTo;
 import androidx.collection.ArrayMap;
 import androidx.core.app.BundleCompat;
 import androidx.core.util.Pair;
 import androidx.media.MediaSessionManager.RemoteUserInfo;

 import java.io.FileDescriptor;
 import java.io.PrintWriter;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;

 /**
  * Base class for media browse services.
  * <p>
  * Media browse services enable applications to browse media content provided by an application
  * and ask the application to start playing it. They may also be used to control content that
  * is already playing by way of a {@link MediaSessionCompat}.
  * </p>
  *
  * To extend this class, you must declare the service in your manifest file with
  * an intent filter with the {@link #SERVICE_INTERFACE} action.
  *
  * For example:
  * </p><pre>
  * &lt;service android:name=".MyMediaBrowserServiceCompat"
  *          android:label="&#64;string/service_name" >
  *     &lt;intent-filter>
  *         &lt;action android:name="android.media.browse.MediaBrowserService" />
  *     &lt;/intent-filter>
  * &lt;/service>
  * </pre>
  *
  * <div class="special reference">
  * <h3>Developer Guides</h3>
  * <p>For information about building your media application, read the
  * <a href="{@docRoot}guide/topics/media-apps/index.html">Media Apps</a> developer guide.</p>
  * </div>
  */
 public abstract class MediaBrowserServiceCompat extends Service {
     static final String TAG = "MBServiceCompat";
     static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);

     private static final float EPSILON = 0.00001f;

     private MediaBrowserServiceImpl mImpl;

     /**
      * The {@link Intent} that must be declared as handled by the service.
      */
     public static final String SERVICE_INTERFACE = "android.media.browse.MediaBrowserService";

     /**
      * A key for passing the MediaItem to the ResultReceiver in getItem.
      *
      */
     @RestrictTo(LIBRARY)
     public static final String KEY_MEDIA_ITEM = "media_item";

     /**
      * A key for passing the list of MediaItems to the ResultReceiver in search.
      *
      */
     @RestrictTo(LIBRARY)
     public static final String KEY_SEARCH_RESULTS = "search_results";

     static final int RESULT_FLAG_OPTION_NOT_HANDLED = 1 << 0;
     static final int RESULT_FLAG_ON_LOAD_ITEM_NOT_IMPLEMENTED = 1 << 1;
     static final int RESULT_FLAG_ON_SEARCH_NOT_IMPLEMENTED = 1 << 2;

     /**
      */
     @RestrictTo(LIBRARY)
     public static final int RESULT_ERROR = -1;
     /**
      */
     @RestrictTo(LIBRARY)
     public static final int RESULT_OK = 0;

     /**
      */
     @RestrictTo(LIBRARY)
     public static final int RESULT_PROGRESS_UPDATE = 1;

     @Retention(RetentionPolicy.SOURCE)
     @IntDef(flag = true, value = {RESULT_FLAG_OPTION_NOT_HANDLED,
             RESULT_FLAG_ON_LOAD_ITEM_NOT_IMPLEMENTED, RESULT_FLAG_ON_SEARCH_NOT_IMPLEMENTED})
     private @interface ResultFlags {
     }

     private final ServiceBinderImpl mServiceBinderImpl = new ServiceBinderImpl();
     final ConnectionRecord mConnectionFromFwk = new ConnectionRecord(
             LEGACY_CONTROLLER, UNKNOWN_PID, UNKNOWN_UID, null, null);
     final ArrayList<ConnectionRecord> mPendingConnections = new ArrayList<>();
     final ArrayMap<IBinder, ConnectionRecord> mConnections = new ArrayMap<>();
     ConnectionRecord mCurConnection;
     final ServiceHandler mHandler = new ServiceHandler(/* service= */ this);
     MediaSessionCompat.Token mSession;

     interface MediaBrowserServiceImpl {
         void onCreate();
         IBinder onBind(Intent intent);
         void setSessionToken(MediaSessionCompat.Token token);
         void notifyChildrenChanged(String parentId, Bundle options);
         void notifyChildrenChanged(RemoteUserInfo remoteUserInfo, String parentId, Bundle options);
         Bundle getBrowserRootHints();
         RemoteUserInfo getCurrentBrowserInfo();
     }

     class MediaBrowserServiceImplBase implements MediaBrowserServiceImpl {
         private Messenger mMessenger;

         @Override
         public void onCreate() {
             mMessenger = new Messenger(mHandler);
         }

         @Override
         public IBinder onBind(Intent intent) {
             if (SERVICE_INTERFACE.equals(intent.getAction())) {
                 return mMessenger.getBinder();
             }
             return null;
         }

         @Override
         public void setSessionToken(final MediaSessionCompat.Token token) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     Iterator<ConnectionRecord> iter = mConnections.values().iterator();
                     while (iter.hasNext()) {
                         ConnectionRecord connection = iter.next();
                         try {
                             connection.callbacks.onConnect(connection.root.getRootId(), token,
                                     connection.root.getExtras());
                         } catch (RemoteException e) {
                             Log.w(TAG, "Connection for " + connection.pkg + " is no longer valid.");
                             iter.remove();
                         }
                     }
                 }
             });
         }

         @Override
         public void notifyChildrenChanged(@NonNull final String parentId, final Bundle options) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     for (IBinder binder : mConnections.keySet()) {
                         ConnectionRecord connection = mConnections.get(binder);
                         notifyChildrenChangedOnHandler(connection, parentId, options);
                     }
                 }
             });
         }

         @Override
         public void notifyChildrenChanged(@NonNull final RemoteUserInfo remoteUserInfo,
                 @NonNull final String parentId, final Bundle options) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     for (int i = 0; i < mConnections.size(); i++) {
                         ConnectionRecord connection = mConnections.valueAt(i);
                         if (connection.browserInfo.equals(remoteUserInfo)) {
                             notifyChildrenChangedOnHandler(connection, parentId, options);
                             break;
                         }
                     }
                 }
             });
         }

         @SuppressWarnings("WeakerAccess") /* synthetic access */
         void notifyChildrenChangedOnHandler(final ConnectionRecord connection,
                 final String parentId, final Bundle options) {
             List<Pair<IBinder, Bundle>> callbackList = connection.subscriptions.get(parentId);
             if (callbackList != null) {
                 for (Pair<IBinder, Bundle> callback : callbackList) {
                     if (MediaBrowserCompatUtils.hasDuplicatedItems(options, callback.second)) {
                         performLoadChildren(parentId, connection, callback.second, options);
                     }
                 }
             }
             // Don't break, because multiple remoteUserInfo may match.
         }

         @Override
         public Bundle getBrowserRootHints() {
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onLoadChildren,"
                         + " onLoadItem, onSearch, or onCustomAction methods");
             }
             return mCurConnection.rootHints == null ? null : new Bundle(mCurConnection.rootHints);
         }

         @Override
         public RemoteUserInfo getCurrentBrowserInfo() {
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onLoadChildren,"
                         + " onLoadItem, onSearch, or onCustomAction methods");
             }
             return mCurConnection.browserInfo;
         }
     }

     @RequiresApi(21)
     class MediaBrowserServiceImplApi21 implements MediaBrowserServiceImpl {
         final List<Bundle> mRootExtrasList = new ArrayList<>();
         MediaBrowserService mServiceFwk;
         Messenger mMessenger;

         @Override
         public void onCreate() {
             mServiceFwk = new MediaBrowserServiceApi21(MediaBrowserServiceCompat.this);
             mServiceFwk.onCreate();
         }

         @Override
         public IBinder onBind(Intent intent) {
             return mServiceFwk.onBind(intent);
         }

         @Override
         public void setSessionToken(final MediaSessionCompat.Token token) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     setSessionTokenOnHandler(token);
                 }
             });
         }

         void setSessionTokenOnHandler(MediaSessionCompat.Token token) {
             if (!mRootExtrasList.isEmpty()) {
                 IMediaSession extraBinder = token.getExtraBinder();
                 if (extraBinder != null) {
                     for (Bundle rootExtras : mRootExtrasList) {
                         BundleCompat.putBinder(rootExtras, EXTRA_SESSION_BINDER,
                                 extraBinder.asBinder());
                     }
                 }
                 mRootExtrasList.clear();
             }
             mServiceFwk.setSessionToken((MediaSession.Token) token.getToken());
         }

         @Override
         public void notifyChildrenChanged(final String parentId, final Bundle options) {
             notifyChildrenChangedForFramework(parentId, options);
             notifyChildrenChangedForCompat(parentId, options);
         }

         @Override
         public void notifyChildrenChanged(final RemoteUserInfo remoteUserInfo,
                 final String parentId, final Bundle options) {
             // TODO(Post-P): Need a way to notify to a specific browser in framework.
             notifyChildrenChangedForCompat(remoteUserInfo, parentId, options);
         }

         public BrowserRoot onGetRoot(
                 String clientPackageName, int clientUid, Bundle rootHints) {
             Bundle rootExtras = null;
             int clientPid = UNKNOWN_PID;
             if (rootHints != null && rootHints.getInt(EXTRA_CLIENT_VERSION, 0) != 0) {
                 rootHints.remove(EXTRA_CLIENT_VERSION);
                 mMessenger = new Messenger(mHandler);
                 rootExtras = new Bundle();
                 rootExtras.putInt(EXTRA_SERVICE_VERSION, SERVICE_VERSION_CURRENT);
                 BundleCompat.putBinder(rootExtras, EXTRA_MESSENGER_BINDER, mMessenger.getBinder());
                 if (mSession != null) {
                     IMediaSession extraBinder = mSession.getExtraBinder();
                     BundleCompat.putBinder(rootExtras, EXTRA_SESSION_BINDER,
                             extraBinder == null ? null : extraBinder.asBinder());
                 } else {
                     mRootExtrasList.add(rootExtras);
                 }
                 clientPid = rootHints.getInt(EXTRA_CALLING_PID, UNKNOWN_PID);
                 rootHints.remove(EXTRA_CALLING_PID);
             }
             ConnectionRecord connection = new ConnectionRecord(
                     clientPackageName, clientPid, clientUid, rootHints, null);
             // We aren't sure whether this connection request would be accepted.
             // Temporarily set mCurConnection just to make getCurrentBrowserInfo() working.
             mCurConnection = connection;
             BrowserRoot root = MediaBrowserServiceCompat.this.onGetRoot(
                     clientPackageName, clientUid, rootHints);
             mCurConnection = null;
             if (root == null) {
                 return null;
             }
             if (mMessenger != null) {
                 // Keeps the connection request from the MediaBrowserCompat to reuse the package
                 // name here.
                 // Note: Connection will be completed after it gets extra binder call with
                 // CLIENT_MSG_REGISTER_CALLBACK_MESSENGER.
                 mPendingConnections.add(connection);
             }
             if (rootExtras == null) {
                 rootExtras = root.getExtras();
             } else if (root.getExtras() != null) {
                 rootExtras.putAll(root.getExtras());
             }
             return new BrowserRoot(root.getRootId(), rootExtras);
         }

         public void onLoadChildren(String parentId,
                 final ResultWrapper<List<Parcel>> resultWrapper) {
             final Result<List<MediaBrowserCompat.MediaItem>> result =
                     new Result<List<MediaBrowserCompat.MediaItem>>(parentId) {
                         @Override
                         void onResultSent(@Nullable List<MediaBrowserCompat.MediaItem> list) {
                             List<Parcel> parcelList = null;
                             if (list != null) {
                                 parcelList = new ArrayList<>(list.size());
                                 for (MediaBrowserCompat.MediaItem item : list) {
                                     Parcel parcel = Parcel.obtain();
                                     item.writeToParcel(parcel, 0);
                                     parcelList.add(parcel);
                                 }
                             }
                             resultWrapper.sendResult(parcelList);
                         }

                         @Override
                         public void detach() {
                             resultWrapper.detach();
                         }
                     };
             mCurConnection = mConnectionFromFwk;
             MediaBrowserServiceCompat.this.onLoadChildren(parentId, result);
             mCurConnection = null;
         }

         void notifyChildrenChangedForFramework(final String parentId, final Bundle options) {
             mServiceFwk.notifyChildrenChanged(parentId);
         }

         void notifyChildrenChangedForCompat(final String parentId, final Bundle options) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     for (IBinder binder : mConnections.keySet()) {
                         ConnectionRecord connection = mConnections.get(binder);
                         notifyChildrenChangedForCompatOnHandler(connection, parentId, options);
                     }
                 }
             });
         }

         void notifyChildrenChangedForCompat(final RemoteUserInfo remoteUserInfo,
                 final String parentId, final Bundle options) {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     for (int i = 0; i < mConnections.size(); i++) {
                         ConnectionRecord connection = mConnections.valueAt(i);
                         if (connection.browserInfo.equals(remoteUserInfo)) {
                             notifyChildrenChangedForCompatOnHandler(connection, parentId, options);
                         }
                     }
                 }
             });
         }

         @SuppressWarnings("WeakerAccess") /* synthetic access */
         void notifyChildrenChangedForCompatOnHandler(final ConnectionRecord connection,
                 final String parentId, final Bundle options) {
             List<Pair<IBinder, Bundle>> callbackList = connection.subscriptions.get(parentId);
             if (callbackList != null) {
                 for (Pair<IBinder, Bundle> callback : callbackList) {
                     if (MediaBrowserCompatUtils.hasDuplicatedItems(options, callback.second)) {
                         performLoadChildren(parentId, connection, callback.second, options);
                     }
                 }
             }
         }

         @Override
         public Bundle getBrowserRootHints() {
             if (mMessenger == null) {
                 // TODO: Handle getBrowserRootHints when connected with framework MediaBrowser.
                 return null;
             }
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onGetRoot,"
                         + " onLoadChildren, onLoadItem, onSearch, or onCustomAction methods");
             }
             return mCurConnection.rootHints == null ? null : new Bundle(mCurConnection.rootHints);
         }

         @Override
         public RemoteUserInfo getCurrentBrowserInfo() {
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onGetRoot,"
                         + " onLoadChildren, onLoadItem, onSearch, or onCustomAction methods");
             }
             return mCurConnection.browserInfo;
         }

         @RequiresApi(21)
         class MediaBrowserServiceApi21 extends MediaBrowserService {
             MediaBrowserServiceApi21(Context context) {
                 attachBaseContext(context);
             }

             @Override
             public MediaBrowserService.BrowserRoot onGetRoot(String clientPackageName,
                     int clientUid, Bundle rootHints) {
                 MediaSessionCompat.ensureClassLoader(rootHints);
                 MediaBrowserServiceCompat.BrowserRoot browserRootCompat =
                         MediaBrowserServiceImplApi21.this.onGetRoot(clientPackageName, clientUid,
                                 rootHints == null ? null : new Bundle(rootHints));
                 return browserRootCompat == null ? null : new MediaBrowserService.BrowserRoot(
                         browserRootCompat.mRootId, browserRootCompat.mExtras);
             }

             @Override
             public void onLoadChildren(String parentId,
                     Result<List<MediaBrowser.MediaItem>> result) {
                 MediaBrowserServiceImplApi21.this.onLoadChildren(parentId,
                         new ResultWrapper<List<Parcel>>(result));
             }
         }
     }

     @RequiresApi(23)
     class MediaBrowserServiceImplApi23 extends MediaBrowserServiceImplApi21 {
         @Override
         public void onCreate() {
             mServiceFwk = new MediaBrowserServiceApi23(MediaBrowserServiceCompat.this);
             mServiceFwk.onCreate();
         }

         public void onLoadItem(String itemId, final ResultWrapper<Parcel> resultWrapper) {
             final Result<MediaBrowserCompat.MediaItem> result =
                     new Result<MediaBrowserCompat.MediaItem>(itemId) {
                         @Override
                         void onResultSent(@Nullable MediaBrowserCompat.MediaItem item) {
                             if (item == null) {
                                 resultWrapper.sendResult(null);
                             } else {
                                 Parcel parcelItem = Parcel.obtain();
                                 item.writeToParcel(parcelItem, 0);
                                 resultWrapper.sendResult(parcelItem);
                             }
                         }

                         @Override
                         public void detach() {
                             resultWrapper.detach();
                         }
                     };
             mCurConnection = mConnectionFromFwk;
             MediaBrowserServiceCompat.this.onLoadItem(itemId, result);
             mCurConnection = null;
         }

         class MediaBrowserServiceApi23 extends MediaBrowserServiceApi21 {
             MediaBrowserServiceApi23(Context context) {
                 super(context);
             }

             @Override
             public void onLoadItem(String itemId, Result<MediaBrowser.MediaItem> result) {
                 MediaBrowserServiceImplApi23.this.onLoadItem(itemId,
                         new ResultWrapper<Parcel>(result));
             }
         }
     }

     @RequiresApi(26)
     class MediaBrowserServiceImplApi26 extends MediaBrowserServiceImplApi23 {
         @Override
         public void onCreate() {
             mServiceFwk = new MediaBrowserServiceApi26(MediaBrowserServiceCompat.this);
             mServiceFwk.onCreate();
         }

         public void onLoadChildren(String parentId,
                 final ResultWrapper<List<Parcel>> resultWrapper,
                 final Bundle options) {
             final Result<List<MediaBrowserCompat.MediaItem>> result =
                     new Result<List<MediaBrowserCompat.MediaItem>>(parentId) {
                         @Override
                         void onResultSent(@Nullable List<MediaBrowserCompat.MediaItem> list) {
                             if (list == null) {
                                 resultWrapper.sendResult(null);
                                 return;
                             }
                             if ((getFlags() & RESULT_FLAG_OPTION_NOT_HANDLED) != 0) {
                                 // If onLoadChildren(options) is not overridden, the list we get
                                 // here is not paginated. Therefore, we need to manually cut
                                 // the list. In other words, we need to apply options here.
                                 list = applyOptions(list, options);
                             }
                             List<Parcel> parcelList = new ArrayList<>(list.size());
                             for (MediaBrowserCompat.MediaItem item : list) {
                                 Parcel parcel = Parcel.obtain();
                                 item.writeToParcel(parcel, 0);
                                 parcelList.add(parcel);
                             }
                             resultWrapper.sendResult(parcelList);
                         }

                         @Override
                         public void detach() {
                             resultWrapper.detach();
                         }
                     };
             mCurConnection = mConnectionFromFwk;
             MediaBrowserServiceCompat.this.onLoadChildren(parentId, result, options);
             mCurConnection = null;
         }

         @Override
         public Bundle getBrowserRootHints() {
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onGetRoot,"
                         + " onLoadChildren, onLoadItem, onSearch, or onCustomAction methods");
             }
             if (mCurConnection == mConnectionFromFwk) {
                 return mServiceFwk.getBrowserRootHints();
             }
             return mCurConnection.rootHints == null ? null : new Bundle(mCurConnection.rootHints);
         }

         @Override
         void notifyChildrenChangedForFramework(final String parentId, final Bundle options) {
             if (options != null) {
                 mServiceFwk.notifyChildrenChanged(parentId, options);
             } else {
                 super.notifyChildrenChangedForFramework(parentId, options);
             }
         }

         class MediaBrowserServiceApi26 extends MediaBrowserServiceApi23 {
             MediaBrowserServiceApi26(Context context) {
                 super(context);
             }

             @Override
             public void onLoadChildren(String parentId, Result<List<MediaBrowser.MediaItem>> result,
                     Bundle options) {
                 MediaSessionCompat.ensureClassLoader(options);
                 mCurConnection = mConnectionFromFwk;
                 MediaBrowserServiceImplApi26.this.onLoadChildren(parentId,
                         new ResultWrapper<List<Parcel>>(result), options);
                 mCurConnection = null;
             }
         }
     }

     @RequiresApi(28)
     class MediaBrowserServiceImplApi28 extends MediaBrowserServiceImplApi26 {
         @Override
         public RemoteUserInfo getCurrentBrowserInfo() {
             if (mCurConnection == null) {
                 throw new IllegalStateException("This should be called inside of onGetRoot,"
                         + " onLoadChildren, onLoadItem, onSearch, or onCustomAction methods");
             }
             if (mCurConnection == mConnectionFromFwk) {
                 return new RemoteUserInfo(mServiceFwk.getCurrentBrowserInfo());
             }
             return mCurConnection.browserInfo;
         }
     }

     private static final class ServiceHandler extends Handler {

         // Must only be accessed on the main thread.
         @Nullable private MediaBrowserServiceCompat mService;

         @MainThread
         ServiceHandler(@NonNull MediaBrowserServiceCompat service) {
             mService = service;
         }

         @Override
         @MainThread
         public void handleMessage(@NonNull Message msg) {
             if (mService != null) {
                 mService.handleMessageInternal(msg);
             } else {
                 removeCallbacksAndMessages(/* token= */ null);
             }
         }

         @MainThread
         public void release() {
             mService = null;
         }

         @Override
         public boolean sendMessageAtTime(Message msg, long uptimeMillis) {
             // Binder.getCallingUid() in handleMessage will return the uid of this process.
             // In order to get the right calling uid, Binder.getCallingUid() should be called here.
             Bundle data = msg.getData();
             data.setClassLoader(MediaBrowserCompat.class.getClassLoader());
             data.putInt(DATA_CALLING_UID, Binder.getCallingUid());
             int pid = Binder.getCallingPid();
             if (pid > 0) {
                 data.putInt(DATA_CALLING_PID, pid);
             } else if (!data.containsKey(DATA_CALLING_PID)) {
                 // If the MediaBrowserCompat didn't send its PID, then put UNKNOWN_PID.
                 data.putInt(DATA_CALLING_PID, UNKNOWN_PID);
             }
             return super.sendMessageAtTime(msg, uptimeMillis);
         }

         public void postOrRun(Runnable r) {
             if (Thread.currentThread() == getLooper().getThread()) {
                 r.run();
             } else {
                 post(r);
             }
         }
     }

     /**
      * All the info about a connection.
      */
     private class ConnectionRecord implements IBinder.DeathRecipient {
         public final String pkg;
         public final int pid;
         public final int uid;
         public final RemoteUserInfo browserInfo;
         public final Bundle rootHints;
         public final ServiceCallbacks callbacks;
         public final HashMap<String, List<Pair<IBinder, Bundle>>> subscriptions = new HashMap<>();
         public BrowserRoot root;

         ConnectionRecord(String pkg, int pid, int uid, Bundle rootHints,
                 ServiceCallbacks callback) {
             this.pkg = pkg;
             this.pid = pid;
             this.uid = uid;
             this.browserInfo = new RemoteUserInfo(pkg, pid, uid);
             this.rootHints = rootHints;
             this.callbacks = callback;
         }

         @Override
         public void binderDied() {
             mHandler.post(new Runnable() {
                 @Override
                 public void run() {
                     mConnections.remove(callbacks.asBinder());
                 }
             });
         }
     }

     /**
      * Completion handler for asynchronous callback methods in {@link MediaBrowserServiceCompat}.
      * <p>
      * Each of the methods that takes one of these to send the result must call either
      * {@link #sendResult} or {@link #sendError} to respond to the caller with the given results or
      * errors. If those functions return without calling {@link #sendResult} or {@link #sendError},
      * they must instead call {@link #detach} before returning, and then may call
      * {@link #sendResult} or {@link #sendError} when they are done. If {@link #sendResult},
      * {@link #sendError}, or {@link #detach} is called twice, an exception will be thrown.
      * </p><p>
      * Those functions might also want to call {@link #sendProgressUpdate} to send interim updates
      * to the caller. If it is called after calling {@link #sendResult} or {@link #sendError}, an
      * exception will be thrown.
      * </p>
      *
      * @see MediaBrowserServiceCompat#onLoadChildren
      * @see MediaBrowserServiceCompat#onLoadItem
      * @see MediaBrowserServiceCompat#onSearch
      * @see MediaBrowserServiceCompat#onCustomAction
      */
     public static class Result<T> {
         private final Object mDebug;
         private boolean mDetachCalled;
         private boolean mSendResultCalled;
         private boolean mSendErrorCalled;
         private int mFlags;

         Result(Object debug) {
             mDebug = debug;
         }

         /**
          * Send the result back to the caller.
          */
         public void sendResult(@Nullable T result) {
             if (mSendResultCalled || mSendErrorCalled) {
                 throw new IllegalStateException("sendResult() called when either sendResult() or "
                         + "sendError() had already been called for: " + mDebug);
             }
             mSendResultCalled = true;
             onResultSent(result);
         }

         /**
          * Send an interim update to the caller. This method is supported only when it is used in
          * {@link #onCustomAction}.
          *
          * @param extras A bundle that contains extra data.
          */
         public void sendProgressUpdate(@Nullable Bundle extras) {
             if (mSendResultCalled || mSendErrorCalled) {
                 throw new IllegalStateException("sendProgressUpdate() called when either "
                         + "sendResult() or sendError() had already been called for: " + mDebug);
             }
             checkExtraFields(extras);
             onProgressUpdateSent(extras);
         }

         /**
          * Notify the caller of a failure. This is supported only when it is used in
          * {@link #onCustomAction}.
          *
          * @param extras A bundle that contains extra data.
          */
         public void sendError(@Nullable Bundle extras) {
             if (mSendResultCalled || mSendErrorCalled) {
                 throw new IllegalStateException("sendError() called when either sendResult() or "
                         + "sendError() had already been called for: " + mDebug);
             }
             mSendErrorCalled = true;
             onErrorSent(extras);
         }

         /**
          * Detach this message from the current thread and allow the {@link #sendResult}
          * call to happen later.
          */
         public void detach() {
             if (mDetachCalled) {
                 throw new IllegalStateException("detach() called when detach() had already"
                         + " been called for: " + mDebug);
             }
             if (mSendResultCalled) {
                 throw new IllegalStateException("detach() called when sendResult() had already"
                         + " been called for: " + mDebug);
             }
             if (mSendErrorCalled) {
                 throw new IllegalStateException("detach() called when sendError() had already"
                         + " been called for: " + mDebug);
             }
             mDetachCalled = true;
         }

         boolean isDone() {
             return mDetachCalled || mSendResultCalled || mSendErrorCalled;
         }

         void setFlags(@ResultFlags int flags) {
             mFlags = flags;
         }

         int getFlags() {
             return mFlags;
         }

         /**
          * Called when the result is sent, after assertions about not being called twice have
          * happened.
          */
         void onResultSent(@Nullable T result) {
         }

         /**
          * Called when an interim update is sent.
          */
         void onProgressUpdateSent(@Nullable Bundle extras) {
             throw new UnsupportedOperationException("It is not supported to send an interim update "
                     + "for " + mDebug);
         }

         /**
          * Called when an error is sent, after assertions about not being called twice have
          * happened.
          */
         void onErrorSent(@Nullable Bundle extras) {
             throw new UnsupportedOperationException("It is not supported to send an error for "
                     + mDebug);
         }

         private void checkExtraFields(@Nullable Bundle extras) {
             if (extras == null) {
                 return;
             }
             if (extras.containsKey(MediaBrowserCompat.EXTRA_DOWNLOAD_PROGRESS)) {
                 float value = extras.getFloat(MediaBrowserCompat.EXTRA_DOWNLOAD_PROGRESS);
                 if (value < -EPSILON || value > 1.0f + EPSILON) {
                     throw new IllegalArgumentException("The value of the EXTRA_DOWNLOAD_PROGRESS "
                             + "field must be a float number within [0.0, 1.0]");
                 }
             }
         }
     }

     private class ServiceBinderImpl {
         ServiceBinderImpl() {
         }

         public void connect(final String pkg, final int pid, final int uid, final Bundle rootHints,
                 final ServiceCallbacks callbacks) {

             if (!isValidPackage(pkg, uid)) {
                 throw new IllegalArgumentException("Package/uid mismatch: uid=" + uid
                         + " package=" + pkg);
             }

             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     // Clear out the old subscriptions. We are getting new ones.
                     mConnections.remove(b);

                     final ConnectionRecord connection = new ConnectionRecord(pkg, pid, uid,
                             rootHints, callbacks);
                     mCurConnection = connection;
                     connection.root = MediaBrowserServiceCompat.this.onGetRoot(pkg, uid, rootHints);
                     mCurConnection = null;

                     // If they didn't return something, don't allow this client.
                     if (connection.root == null) {
                         Log.i(TAG, "No root for client " + pkg + " from service "
                                 + getClass().getName());
                         try {
                             callbacks.onConnectFailed();
                         } catch (RemoteException ex) {
                             Log.w(TAG, "Calling onConnectFailed() failed. Ignoring. "
                                     + "pkg=" + pkg);
                         }
                     } else {
                         try {
                             mConnections.put(b, connection);
                             b.linkToDeath(connection, 0);
                             if (mSession != null) {
                                 callbacks.onConnect(connection.root.getRootId(),
                                         mSession, connection.root.getExtras());
                             }
                         } catch (RemoteException ex) {
                             Log.w(TAG, "Calling onConnect() failed. Dropping client. "
                                     + "pkg=" + pkg);
                             mConnections.remove(b);
                         }
                     }
                 }
             });
         }

         public void disconnect(final ServiceCallbacks callbacks) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     // Clear out the old subscriptions. We are getting new ones.
                     final ConnectionRecord old = mConnections.remove(b);
                     if (old != null) {
                         // TODO
                         old.callbacks.asBinder().unlinkToDeath(old, 0);
                     }
                 }
             });
         }

         public void addSubscription(final String id, final IBinder token, final Bundle options,
                 final ServiceCallbacks callbacks) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     // Get the record for the connection
                     final ConnectionRecord connection = mConnections.get(b);
                     if (connection == null) {
                         Log.w(TAG, "addSubscription for callback that isn't registered id="
                                 + id);
                         return;
                     }

                     MediaBrowserServiceCompat.this.addSubscription(id, connection, token, options);
                 }
             });
         }

         public void removeSubscription(final String id, final IBinder token,
                 final ServiceCallbacks callbacks) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     ConnectionRecord connection = mConnections.get(b);
                     if (connection == null) {
                         Log.w(TAG, "removeSubscription for callback that isn't registered id="
                                 + id);
                         return;
                     }
                     if (!MediaBrowserServiceCompat.this.removeSubscription(
                             id, connection, token)) {
                         Log.w(TAG, "removeSubscription called for " + id
                                 + " which is not subscribed");
                     }
                 }
             });
         }

         public void getMediaItem(final String mediaId, final ResultReceiver receiver,
                 final ServiceCallbacks callbacks) {
             if (TextUtils.isEmpty(mediaId) || receiver == null) {
                 return;
             }

             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     ConnectionRecord connection = mConnections.get(b);
                     if (connection == null) {
                         Log.w(TAG, "getMediaItem for callback that isn't registered id=" + mediaId);
                         return;
                     }
                     performLoadItem(mediaId, connection, receiver);
                 }
             });
         }

         // Used when {@link MediaBrowserProtocol#EXTRA_MESSENGER_BINDER} is used.
         public void registerCallbacks(final ServiceCallbacks callbacks, final String pkg,
                 final int pid, final int uid, final Bundle rootHints) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();
                     // Clear out the old subscriptions. We are getting new ones.
                     mConnections.remove(b);

                     ConnectionRecord connection = null;
                     Iterator<ConnectionRecord> iter = mPendingConnections.iterator();
                     while (iter.hasNext()) {
                         ConnectionRecord pendingConnection = iter.next();
                         // Note: We cannot use Map/Set for mPendingConnections but List because
                         // multiple MediaBrowserCompats with the same UID can request connect.
                         if (pendingConnection.uid == uid) {
                             // If caller hasn't set pkg and pid, do the best effort to get it.
                             if (TextUtils.isEmpty(pkg) || pid <= 0) {
                                 // Note: Do not assign pendingConnection directly because it doesn't
                                 // have callback information.
                                 connection = new ConnectionRecord(pendingConnection.pkg,
                                         pendingConnection.pid, pendingConnection.uid,
                                         rootHints, callbacks);
                             }
                             iter.remove();
                             break;
                         }
                     }
                     if (connection == null) {
                         connection = new ConnectionRecord(pkg, pid, uid, rootHints, callbacks);
                     }
                     mConnections.put(b, connection);
                     try {
                         b.linkToDeath(connection, 0);
                     } catch (RemoteException e) {
                         Log.w(TAG, "IBinder is already dead.");
                     }
                 }
             });
         }

         // Used when {@link MediaBrowserProtocol#EXTRA_MESSENGER_BINDER} is used.
         public void unregisterCallbacks(final ServiceCallbacks callbacks) {
             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();
                     ConnectionRecord old = mConnections.remove(b);
                     if (old != null) {
                         b.unlinkToDeath(old, 0);
                     }
                 }
             });
         }

         public void search(final String query, final Bundle extras, final ResultReceiver receiver,
                 final ServiceCallbacks callbacks) {
             if (TextUtils.isEmpty(query) || receiver == null) {
                 return;
             }

             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     ConnectionRecord connection = mConnections.get(b);
                     if (connection == null) {
                         Log.w(TAG, "search for callback that isn't registered query=" + query);
                         return;
                     }
                     performSearch(query, extras, connection, receiver);
                 }
             });
         }

         public void sendCustomAction(final String action, final Bundle extras,
                 final ResultReceiver receiver, final ServiceCallbacks callbacks) {
             if (TextUtils.isEmpty(action) || receiver == null) {
                 return;
             }

             mHandler.postOrRun(new Runnable() {
                 @Override
                 public void run() {
                     final IBinder b = callbacks.asBinder();

                     ConnectionRecord connection = mConnections.get(b);
                     if (connection == null) {
                         Log.w(TAG, "sendCustomAction for callback that isn't registered action="
                                 + action + ", extras=" + extras);
                         return;
                     }
                     performCustomAction(action, extras, connection, receiver);
                 }
             });
         }
     }

     private interface ServiceCallbacks {
         IBinder asBinder();
         void onConnect(String root, MediaSessionCompat.Token session, Bundle extras)
                 throws RemoteException;
         void onConnectFailed() throws RemoteException;
         void onLoadChildren(String mediaId, List<MediaBrowserCompat.MediaItem> list, Bundle options,
                 Bundle notifyChildrenChangedOptions) throws RemoteException;
     }

     private static class ServiceCallbacksCompat implements ServiceCallbacks {
         final Messenger mCallbacks;

         ServiceCallbacksCompat(Messenger callbacks) {
             mCallbacks = callbacks;
         }

         @Override
         public IBinder asBinder() {
             return mCallbacks.getBinder();
         }

         @Override
         public void onConnect(String root, MediaSessionCompat.Token session, Bundle extras)
                 throws RemoteException {
             if (extras == null) {
                 extras = new Bundle();
             }
             extras.putInt(EXTRA_SERVICE_VERSION, SERVICE_VERSION_CURRENT);
             Bundle data = new Bundle();
             data.putString(DATA_MEDIA_ITEM_ID, root);
             data.putParcelable(DATA_MEDIA_SESSION_TOKEN, session);
             data.putBundle(DATA_ROOT_HINTS, extras);
             sendRequest(SERVICE_MSG_ON_CONNECT, data);
         }

         @Override
         public void onConnectFailed() throws RemoteException {
             sendRequest(SERVICE_MSG_ON_CONNECT_FAILED, null);
         }

         @SuppressWarnings({"rawtypes", "unchecked"})
         @Override
         public void onLoadChildren(String mediaId, List<MediaBrowserCompat.MediaItem> list,
                 Bundle options, Bundle notifyChildrenChangedOptions) throws RemoteException {
             Bundle data = new Bundle();
             data.putString(DATA_MEDIA_ITEM_ID, mediaId);
             data.putBundle(DATA_OPTIONS, options);
             data.putBundle(DATA_NOTIFY_CHILDREN_CHANGED_OPTIONS, notifyChildrenChangedOptions);
             if (list != null) {
                 data.putParcelableArrayList(DATA_MEDIA_ITEM_LIST,
                         list instanceof ArrayList ? (ArrayList) list : new ArrayList<>(list));
             }
             sendRequest(SERVICE_MSG_ON_LOAD_CHILDREN, data);
         }

         private void sendRequest(int what, Bundle data) throws RemoteException {
             Message msg = Message.obtain();
             msg.what = what;
             msg.arg1 = SERVICE_VERSION_CURRENT;
             msg.setData(data);
             mCallbacks.send(msg);
         }
     }

     @RequiresApi(21)
     @SuppressWarnings({"rawtypes", "unchecked"})
     static class ResultWrapper<T> {
         MediaBrowserService.Result mResultFwk;

         ResultWrapper(MediaBrowserService.Result result) {
             mResultFwk = result;
         }

         public void sendResult(T result) {
             if (result instanceof List) {
                 mResultFwk.sendResult(parcelListToItemList((List<Parcel>) result));
             } else if (result instanceof Parcel) {
                 Parcel parcel = (Parcel) result;
                 parcel.setDataPosition(0);
                 mResultFwk.sendResult(MediaBrowser.MediaItem.CREATOR.createFromParcel(parcel));
                 parcel.recycle();
             } else {
                 // The result is null or an invalid instance.
                 mResultFwk.sendResult(null);
             }
         }

         public void detach() {
             mResultFwk.detach();
         }

         List<MediaBrowser.MediaItem> parcelListToItemList(List<Parcel> parcelList) {
             if (parcelList == null) {
                 return null;
             }
             List<MediaBrowser.MediaItem> items = new ArrayList<>(parcelList.size());
             for (Parcel parcel : parcelList) {
                 parcel.setDataPosition(0);
                 items.add(MediaBrowser.MediaItem.CREATOR.createFromParcel(parcel));
                 parcel.recycle();
             }
             return items;
         }
     }

     /**
      * Attaches to the base context. This method is added to change the visibility of
      * {@link Service#attachBaseContext(Context)}.
      * <p>
      * Note that we cannot simply override {@link Service#attachBaseContext(Context)} and hide it
      * because lint checks considers the overriden method as the new public API that needs update
      * of current.txt.
      *
      */
     @RestrictTo(LIBRARY_GROUP_PREFIX) // accessed by media2-session
     public void attachToBaseContext(Context base) {
         attachBaseContext(base);
     }

     @Override
     public void onCreate() {
         super.onCreate();
         if (Build.VERSION.SDK_INT >= 28) {
             mImpl = new MediaBrowserServiceImplApi28();
         } else if (Build.VERSION.SDK_INT >= 26) {
             mImpl = new MediaBrowserServiceImplApi26();
         } else if (Build.VERSION.SDK_INT >= 23) {
             mImpl = new MediaBrowserServiceImplApi23();
         } else if (Build.VERSION.SDK_INT >= 21) {
             mImpl = new MediaBrowserServiceImplApi21();
         } else {
             mImpl = new MediaBrowserServiceImplBase();
         }
         mImpl.onCreate();
     }

     @CallSuper
     @MainThread
     @Override
     public void onDestroy() {
         mHandler.release();
     }

     @Override
     public IBinder onBind(Intent intent) {
         return mImpl.onBind(intent);
     }

     @Override
     public void dump(FileDescriptor fd, PrintWriter writer, String[] args) {
     }

     /**
      * Called to get the root information for browsing by a particular client.
      * <p>
      * The implementation should verify that the client package has permission
      * to access browse media information before returning the root id; it
      * should return null if the client is not allowed to access this
      * information.
      * </p>
      *
      * @param clientPackageName The package name of the application which is
      *            requesting access to browse media.
      * @param clientUid The uid of the application which is requesting access to
      *            browse media.
      * @param rootHints An optional bundle of service-specific arguments to send
      *            to the media browse service when connecting and retrieving the
      *            root id for browsing, or null if none. The contents of this
      *            bundle may affect the information returned when browsing.
      * @return The {@link BrowserRoot} for accessing this app's content or null.
      * @see BrowserRoot#EXTRA_RECENT
      * @see BrowserRoot#EXTRA_OFFLINE
      * @see BrowserRoot#EXTRA_SUGGESTED
      */
     public abstract @Nullable BrowserRoot onGetRoot(@NonNull String clientPackageName,
             int clientUid, @Nullable Bundle rootHints);

     /**
      * Called to get information about the children of a media item.
      * <p>
      * Implementations must call {@link Result#sendResult result.sendResult}
      * with the list of children. If loading the children will be an expensive
      * operation that should be performed on another thread,
      * {@link Result#detach result.detach} may be called before returning from
      * this function, and then {@link Result#sendResult result.sendResult}
      * called when the loading is complete.
      * </p><p>
      * In case the media item does not have any children, call {@link Result#sendResult}
      * with an empty list. When the given {@code parentId} is invalid, implementations must
      * call {@link Result#sendResult result.sendResult} with {@code null}, which will invoke
      * {@link MediaBrowserCompat.SubscriptionCallback#onError}.
      * </p>
      *
      * @param parentId The id of the parent media item whose children are to be
      *            queried.
      * @param result The Result to send the list of children to.
      */
     public abstract void onLoadChildren(@NonNull String parentId,
             @NonNull Result<List<MediaBrowserCompat.MediaItem>> result);

     /**
      * Called to get information about the children of a media item.
      * <p>
      * Implementations must call {@link Result#sendResult result.sendResult}
      * with the list of children. If loading the children will be an expensive
      * operation that should be performed on another thread,
      * {@link Result#detach result.detach} may be called before returning from
      * this function, and then {@link Result#sendResult result.sendResult}
      * called when the loading is complete.
      * </p><p>
      * In case the media item does not have any children, call {@link Result#sendResult}
      * with an empty list. When the given {@code parentId} is invalid, implementations must
      * call {@link Result#sendResult result.sendResult} with {@code null}, which will invoke
      * {@link MediaBrowserCompat.SubscriptionCallback#onError}.
      * </p>
      *
      * @param parentId The id of the parent media item whose children are to be
      *            queried.
      * @param result The Result to send the list of children to.
      * @param options A bundle of service-specific arguments sent from the media
      *            browse. The information returned through the result should be
      *            affected by the contents of this bundle.
      */
     public void onLoadChildren(@NonNull String parentId,
             @NonNull Result<List<MediaBrowserCompat.MediaItem>> result, @NonNull Bundle options) {
         // To support backward compatibility, when the implementation of MediaBrowserService doesn't
         // override onLoadChildren() with options, onLoadChildren() without options will be used
         // instead, and the options will be applied in the implementation of result.onResultSent().
         result.setFlags(RESULT_FLAG_OPTION_NOT_HANDLED);
         onLoadChildren(parentId, result);
     }

     /**
      * Called when a {@link MediaBrowserCompat#subscribe} is called.
      *
      * @param id id
      * @param option option
      */
     @RestrictTo(LIBRARY_GROUP_PREFIX)
     public void onSubscribe(String id, Bundle option) {
     }

     /**
      * Called when a {@link MediaBrowserCompat#unsubscribe} is called.
      *
      * @param id
      */
     @RestrictTo(LIBRARY_GROUP_PREFIX)
     public void onUnsubscribe(String id) {
     }

     /**
      * Called to get information about a specific media item.
      * <p>
      * Implementations must call {@link Result#sendResult result.sendResult}. If
      * loading the item will be an expensive operation {@link Result#detach
      * result.detach} may be called before returning from this function, and
      * then {@link Result#sendResult result.sendResult} called when the item has
      * been loaded.
      * </p><p>
      * When the given {@code itemId} is invalid, implementations must call
      * {@link Result#sendResult result.sendResult} with {@code null}.
      * </p><p>
      * The default implementation will invoke {@link MediaBrowserCompat.ItemCallback#onError}.
      *
      * @param itemId The id for the specific {@link MediaBrowserCompat.MediaItem}.
      * @param result The Result to send the item to, or null if the id is
      *            invalid.
      */
     public void onLoadItem(String itemId, @NonNull Result<MediaBrowserCompat.MediaItem> result) {
         result.setFlags(RESULT_FLAG_ON_LOAD_ITEM_NOT_IMPLEMENTED);
         result.sendResult(null);
     }

     /**
      * Called to get the search result.
      * <p>
      * Implementations must call {@link Result#sendResult result.sendResult}. If the search will be
      * an expensive operation {@link Result#detach result.detach} may be called before returning
      * from this function, and then {@link Result#sendResult result.sendResult} called when the
      * search has been completed.
      * </p><p>
      * In case there are no search results, call {@link Result#sendResult result.sendResult} with an
      * empty list. In case there are some errors happened, call {@link Result#sendResult
      * result.sendResult} with {@code null}, which will invoke {@link
      * MediaBrowserCompat.SearchCallback#onError}.
      * </p><p>
      * The default implementation will invoke {@link MediaBrowserCompat.SearchCallback#onError}.
      * </p>
      *
      * @param query The search query sent from the media browser. It contains keywords separated
      *            by space.
      * @param extras The bundle of service-specific arguments sent from the media browser.
      * @param result The {@link Result} to send the search result.
      */
     public void onSearch(@NonNull String query, Bundle extras,
             @NonNull Result<List<MediaBrowserCompat.MediaItem>> result) {
         result.setFlags(RESULT_FLAG_ON_SEARCH_NOT_IMPLEMENTED);
         result.sendResult(null);
     }

     /**
      * Called to request a custom action to this service.
      * <p>
      * Implementations must call either {@link Result#sendResult} or {@link Result#sendError}. If
      * the requested custom action will be an expensive operation {@link Result#detach} may be
      * called before returning from this function, and then the service can send the result later
      * when the custom action is completed. Implementation can also call
      * {@link Result#sendProgressUpdate} to send an interim update to the requester.
      * </p><p>
      * If the requested custom action is not supported by this service, call
      * {@link Result#sendError}. The default implementation will invoke {@link Result#sendError}.
      * </p>
      *
      * @param action The custom action sent from the media browser.
      * @param extras The bundle of service-specific arguments sent from the media browser.
      * @param result The {@link Result} to send the result of the requested custom action.
      * @see MediaBrowserCompat#CUSTOM_ACTION_DOWNLOAD
      * @see MediaBrowserCompat#CUSTOM_ACTION_REMOVE_DOWNLOADED_FILE
      */
     public void onCustomAction(@NonNull String action, Bundle extras,
             @NonNull Result<Bundle> result) {
         result.sendError(null);
     }

     /**
      * Call to set the media session.
      * <p>
      * This should be called as soon as possible during the service's startup.
      * It may only be called once.
      *
      * @param token The token for the service's {@link MediaSessionCompat}.
      */
     public void setSessionToken(MediaSessionCompat.Token token) {
         if (token == null) {
             throw new IllegalArgumentException("Session token may not be null");
         }
         if (mSession != null) {
             throw new IllegalStateException("The session token has already been set");
         }
         mSession = token;
         mImpl.setSessionToken(token);
     }

     /**
      * Gets the session token, or null if it has not yet been created
      * or if it has been destroyed.
      */
     @Nullable
     public MediaSessionCompat.Token getSessionToken() {
         return mSession;
     }

     /**
      * Gets the root hints sent from the currently connected {@link MediaBrowserCompat}.
      * The root hints are service-specific arguments included in an optional bundle sent to the
      * media browser service when connecting and retrieving the root id for browsing, or null if
      * none. The contents of this bundle may affect the information returned when browsing.
      * <p>
      * Note that this will return null when connected to {@link android.media.browse.MediaBrowser}
      * and running on API 23 or lower.
      *
      * @throws IllegalStateException If this method is called outside of {@link #onLoadChildren},
      *             {@link #onLoadItem} or {@link #onSearch}.
      * @see MediaBrowserServiceCompat.BrowserRoot#EXTRA_RECENT
      * @see MediaBrowserServiceCompat.BrowserRoot#EXTRA_OFFLINE
      * @see MediaBrowserServiceCompat.BrowserRoot#EXTRA_SUGGESTED
      */
     public final Bundle getBrowserRootHints() {
         return mImpl.getBrowserRootHints();
     }

     /**
      * Gets the browser information who sent the current request.
      *
      * @throws IllegalStateException If this method is called outside of {@link #onGetRoot} or
      *             {@link #onLoadChildren} or {@link #onLoadItem}.
      * @see MediaSessionManager#isTrustedForMediaControl(RemoteUserInfo)
      */
     @NonNull
     public final RemoteUserInfo getCurrentBrowserInfo() {
         return mImpl.getCurrentBrowserInfo();
     }

     /**
      * Notifies all connected media browsers that the children of
      * the specified parent id have changed in some way.
      * This will cause browsers to fetch subscribed content again.
      *
      * @param parentId The id of the parent media item whose
      * children changed.
      */
     public void notifyChildrenChanged(@NonNull String parentId) {
         if (parentId == null) {
             throw new IllegalArgumentException("parentId cannot be null in notifyChildrenChanged");
         }
         mImpl.notifyChildrenChanged(parentId, null);
     }

     /**
      * Notifies all connected media browsers that the children of
      * the specified parent id have changed in some way.
      * This will cause browsers to fetch subscribed content again.
      *
      * @param parentId The id of the parent media item whose
      *            children changed.
      * @param options A bundle of service-specific arguments to send
      *            to the media browse. The contents of this bundle may
      *            contain the information about the change.
      */
     public void notifyChildrenChanged(@NonNull String parentId, @NonNull Bundle options) {
         if (parentId == null) {
             throw new IllegalArgumentException("parentId cannot be null in notifyChildrenChanged");
         }
         if (options == null) {
             throw new IllegalArgumentException("options cannot be null in notifyChildrenChanged");
         }
         mImpl.notifyChildrenChanged(parentId, options);
     }

     /**
      * Notifies a connected media browsers that the children of
      * the specified parent id have changed in some way.
      * This will cause browsers to fetch subscribed content again.
      *
      * @param remoteUserInfo to receive this event.
      * @param parentId The id of the parent media item whose
      *            children changed.
      * @param options A bundle of service-specific arguments to send
      *            to the media browse. The contents of this bundle may
      *            contain the information about the change.
      */
     @RestrictTo(LIBRARY_GROUP_PREFIX) // accessed by media2-session
     public void notifyChildrenChanged(@NonNull RemoteUserInfo remoteUserInfo,
             @NonNull String parentId, @NonNull Bundle options) {
         if (remoteUserInfo == null) {
             throw new IllegalArgumentException("remoteUserInfo cannot be null in"
                     + " notifyChildrenChanged");
         }
         if (parentId == null) {
             throw new IllegalArgumentException("parentId cannot be null in notifyChildrenChanged");
         }
         if (options == null) {
             throw new IllegalArgumentException("options cannot be null in notifyChildrenChanged");
         }
         mImpl.notifyChildrenChanged(remoteUserInfo, parentId, options);
     }

     // Package visibility to avoid synthetic accessor.
     /* package */ void handleMessageInternal(Message msg) {
         Bundle data = msg.getData();
         switch (msg.what) {
             case CLIENT_MSG_CONNECT: {
                 Bundle rootHints = data.getBundle(DATA_ROOT_HINTS);
                 MediaSessionCompat.ensureClassLoader(rootHints);

                 mServiceBinderImpl.connect(
                         data.getString(DATA_PACKAGE_NAME),
                         data.getInt(DATA_CALLING_PID),
                         data.getInt(DATA_CALLING_UID),
                         rootHints,
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             }
             case CLIENT_MSG_DISCONNECT:
                 mServiceBinderImpl.disconnect(new ServiceCallbacksCompat(msg.replyTo));
                 break;
             case CLIENT_MSG_ADD_SUBSCRIPTION: {
                 Bundle options = data.getBundle(DATA_OPTIONS);
                 MediaSessionCompat.ensureClassLoader(options);

                 mServiceBinderImpl.addSubscription(
                         data.getString(DATA_MEDIA_ITEM_ID),
                         BundleCompat.getBinder(data, DATA_CALLBACK_TOKEN),
                         options,
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             }
             case CLIENT_MSG_REMOVE_SUBSCRIPTION:
                 mServiceBinderImpl.removeSubscription(
                         data.getString(DATA_MEDIA_ITEM_ID),
                         BundleCompat.getBinder(data, DATA_CALLBACK_TOKEN),
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             case CLIENT_MSG_GET_MEDIA_ITEM:
                 mServiceBinderImpl.getMediaItem(
                         data.getString(DATA_MEDIA_ITEM_ID),
                         (ResultReceiver) data.getParcelable(DATA_RESULT_RECEIVER),
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             case CLIENT_MSG_REGISTER_CALLBACK_MESSENGER: {
                 Bundle rootHints = data.getBundle(DATA_ROOT_HINTS);
                 MediaSessionCompat.ensureClassLoader(rootHints);

                 mServiceBinderImpl.registerCallbacks(
                         new ServiceCallbacksCompat(msg.replyTo),
                         data.getString(DATA_PACKAGE_NAME),
                         data.getInt(DATA_CALLING_PID),
                         data.getInt(DATA_CALLING_UID),
                         rootHints);
                 break;
             }
             case CLIENT_MSG_UNREGISTER_CALLBACK_MESSENGER:
                 mServiceBinderImpl.unregisterCallbacks(new ServiceCallbacksCompat(msg.replyTo));
                 break;
             case CLIENT_MSG_SEARCH: {
                 Bundle searchExtras = data.getBundle(DATA_SEARCH_EXTRAS);
                 MediaSessionCompat.ensureClassLoader(searchExtras);

                 mServiceBinderImpl.search(
                         data.getString(DATA_SEARCH_QUERY),
                         searchExtras,
                         (ResultReceiver) data.getParcelable(DATA_RESULT_RECEIVER),
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             }
             case CLIENT_MSG_SEND_CUSTOM_ACTION: {
                 Bundle customActionExtras = data.getBundle(DATA_CUSTOM_ACTION_EXTRAS);
                 MediaSessionCompat.ensureClassLoader(customActionExtras);

                 mServiceBinderImpl.sendCustomAction(
                         data.getString(DATA_CUSTOM_ACTION),
                         customActionExtras,
                         (ResultReceiver) data.getParcelable(DATA_RESULT_RECEIVER),
                         new ServiceCallbacksCompat(msg.replyTo));
                 break;
             }
             default:
                 Log.w(
                         TAG,
                         "Unhandled message: "
                                 + msg
                                 + "\n  Service version: "
                                 + SERVICE_VERSION_CURRENT
                                 + "\n  Client version: "
                                 + msg.arg1);
         }
     }

     /**
      * Return whether the given package is one of the ones that is owned by the uid.
      */
     boolean isValidPackage(String pkg, int uid) {
         if (pkg == null) {
             return false;
         }
         final PackageManager pm = getPackageManager();
         final String[] packages = pm.getPackagesForUid(uid);
         final int N = packages.length;
         for (int i=0; i<N; i++) {
             if (packages[i].equals(pkg)) {
                 return true;
             }
         }
         return false;
     }

     /**
      * Save the subscription and if it is a new subscription send the results.
      */
     void addSubscription(String id, ConnectionRecord connection, IBinder token,
             Bundle options) {
         // Save the subscription
         List<Pair<IBinder, Bundle>> callbackList = connection.subscriptions.get(id);
         if (callbackList == null) {
             callbackList = new ArrayList<>();
         }
         for (Pair<IBinder, Bundle> callback : callbackList) {
             if (token == callback.first
                     && MediaBrowserCompatUtils.areSameOptions(options, callback.second)) {
                 return;
             }
         }
         callbackList.add(new Pair<>(token, options));
         connection.subscriptions.put(id, callbackList);
         // send the results
         performLoadChildren(id, connection, options, null);

         mCurConnection = connection;
         onSubscribe(id, options);
         mCurConnection = null;
     }

     /**
      * Remove the subscription.
      */
     boolean removeSubscription(String id, ConnectionRecord connection, IBinder token) {
         try {
             if (token == null) {
                 return connection.subscriptions.remove(id) != null;
             }
             boolean removed = false;
             List<Pair<IBinder, Bundle>> callbackList = connection.subscriptions.get(id);
             if (callbackList != null) {
                 Iterator<Pair<IBinder, Bundle>> iter = callbackList.iterator();
                 while (iter.hasNext()) {
                     if (token == iter.next().first) {
                         removed = true;
                         iter.remove();
                     }
                 }
                 if (callbackList.size() == 0) {
                     connection.subscriptions.remove(id);
                 }
             }
             return removed;
         } finally {
             mCurConnection = connection;
             onUnsubscribe(id);
             mCurConnection = null;
         }
     }

     /**
      * Call onLoadChildren and then send the results back to the connection.
      * <p>
      * Callers must make sure that this connection is still connected.
      */
     void performLoadChildren(final String parentId, final ConnectionRecord connection,
             final Bundle subscribeOptions, final Bundle notifyChildrenChangedOptions) {
         final Result<List<MediaBrowserCompat.MediaItem>> result
                 = new Result<List<MediaBrowserCompat.MediaItem>>(parentId) {
             @Override
             void onResultSent(@Nullable List<MediaBrowserCompat.MediaItem> list) {
                 if (mConnections.get(connection.callbacks.asBinder()) != connection) {
                     if (DEBUG) {
                         Log.d(TAG, "Not sending onLoadChildren result for connection that has"
                                 + " been disconnected. pkg=" + connection.pkg + " id=" + parentId);
                     }
                     return;
                 }

                 List<MediaBrowserCompat.MediaItem> filteredList =
                         (getFlags() & RESULT_FLAG_OPTION_NOT_HANDLED) != 0
                                 ? applyOptions(list, subscribeOptions) : list;
                 try {
                     connection.callbacks.onLoadChildren(parentId, filteredList, subscribeOptions,
                             notifyChildrenChangedOptions);
                 } catch (RemoteException ex) {
                     // The other side is in the process of crashing.
                     Log.w(TAG, "Calling onLoadChildren() failed for id=" + parentId
                             + " package=" + connection.pkg);
                 }
             }
         };

         mCurConnection = connection;
         if (subscribeOptions == null) {
             onLoadChildren(parentId, result);
         } else {
             onLoadChildren(parentId, result, subscribeOptions);
         }
         mCurConnection = null;

         if (!result.isDone()) {
             throw new IllegalStateException("onLoadChildren must call detach() or sendResult()"
                     + " before returning for package=" + connection.pkg + " id=" + parentId);
         }
     }

     List<MediaBrowserCompat.MediaItem> applyOptions(List<MediaBrowserCompat.MediaItem> list,
             final Bundle options) {
         if (list == null) {
             return null;
         }
         int page = options.getInt(MediaBrowserCompat.EXTRA_PAGE, -1);
         int pageSize = options.getInt(MediaBrowserCompat.EXTRA_PAGE_SIZE, -1);
         if (page == -1 && pageSize == -1) {
             return list;
         }
         int fromIndex = pageSize * page;
         int toIndex = fromIndex + pageSize;
         if (page < 0 || pageSize < 1 || fromIndex >= list.size()) {
             return Collections.emptyList();
         }
         if (toIndex > list.size()) {
             toIndex = list.size();
         }
         return list.subList(fromIndex, toIndex);
     }

     void performLoadItem(String itemId, ConnectionRecord connection,
             final ResultReceiver receiver) {
         final Result<MediaBrowserCompat.MediaItem> result =
                 new Result<MediaBrowserCompat.MediaItem>(itemId) {
                     @Override
                     void onResultSent(@Nullable MediaBrowserCompat.MediaItem item) {
                         if ((getFlags() & RESULT_FLAG_ON_LOAD_ITEM_NOT_IMPLEMENTED) != 0) {
                             receiver.send(RESULT_ERROR, null);
                             return;
                         }
                         Bundle bundle = new Bundle();
                         bundle.putParcelable(KEY_MEDIA_ITEM, item);
                         receiver.send(RESULT_OK, bundle);
                     }
                 };

         mCurConnection = connection;
         onLoadItem(itemId, result);
         mCurConnection = null;

         if (!result.isDone()) {
             throw new IllegalStateException("onLoadItem must call detach() or sendResult()"
                     + " before returning for id=" + itemId);
         }
     }

     void performSearch(final String query, Bundle extras, ConnectionRecord connection,
             final ResultReceiver receiver) {
         final Result<List<MediaBrowserCompat.MediaItem>> result =
                 new Result<List<MediaBrowserCompat.MediaItem>>(query) {
             @Override
             void onResultSent(@Nullable List<MediaBrowserCompat.MediaItem> items) {
                 if ((getFlags() & RESULT_FLAG_ON_SEARCH_NOT_IMPLEMENTED) != 0
                         || items == null) {
                     receiver.send(RESULT_ERROR, null);
                     return;
                 }
                 Bundle bundle = new Bundle();
                 bundle.putParcelableArray(KEY_SEARCH_RESULTS,
                         items.toArray(new MediaBrowserCompat.MediaItem[0]));
                 receiver.send(RESULT_OK, bundle);
             }
         };

         mCurConnection = connection;
         onSearch(query, extras, result);
         mCurConnection = null;

         if (!result.isDone()) {
             throw new IllegalStateException("onSearch must call detach() or sendResult()"
                     + " before returning for query=" + query);
         }
     }

     void performCustomAction(final String action, Bundle extras, ConnectionRecord connection,
             final ResultReceiver receiver) {
         final Result<Bundle> result = new Result<Bundle>(action) {
                 @Override
                 void onResultSent(@Nullable Bundle result) {
                     receiver.send(RESULT_OK, result);
                 }

                 @Override
                 void onProgressUpdateSent(@Nullable Bundle data) {
                     receiver.send(RESULT_PROGRESS_UPDATE, data);
                 }

                 @Override
                 void onErrorSent(@Nullable Bundle data) {
                     receiver.send(RESULT_ERROR, data);
                 }
             };

         mCurConnection = connection;
         onCustomAction(action, extras, result);
         mCurConnection = null;

         if (!result.isDone()) {
             throw new IllegalStateException("onCustomAction must call detach() or sendResult() or "
                     + "sendError() before returning for action=" + action + " extras="
                     + extras);
         }
     }

     /**
      * Contains information that the browser service needs to send to the client
      * when first connected.
      */
     public static final class BrowserRoot {
         /**
          * The lookup key for a boolean that indicates whether the browser service should return a
          * browser root for recently played media items.
          *
          * <p>When creating a media browser for a given media browser service, this key can be
          * supplied as a root hint for retrieving media items that are recently played.
          * If the media browser service can provide such media items, the implementation must return
          * the key in the root hint when {@link #onGetRoot(String, int, Bundle)} is called back.
          *
          * <p>The root hint may contain multiple keys.
          *
          * @see #EXTRA_OFFLINE
          * @see #EXTRA_SUGGESTED
          */
         public static final String EXTRA_RECENT = "android.service.media.extra.RECENT";

         /**
          * The lookup key for a boolean that indicates whether the browser service should return a
          * browser root for offline media items.
          *
          * <p>When creating a media browser for a given media browser service, this key can be
          * supplied as a root hint for retrieving media items that are can be played without an
          * internet connection.
          * If the media browser service can provide such media items, the implementation must return
          * the key in the root hint when {@link #onGetRoot(String, int, Bundle)} is called back.
          *
          * <p>The root hint may contain multiple keys.
          *
          * @see #EXTRA_RECENT
          * @see #EXTRA_SUGGESTED
          */
         public static final String EXTRA_OFFLINE = "android.service.media.extra.OFFLINE";

         /**
          * The lookup key for a boolean that indicates whether the browser service should return a
          * browser root for suggested media items.
          *
          * <p>When creating a media browser for a given media browser service, this key can be
          * supplied as a root hint for retrieving the media items suggested by the media browser
          * service. The list of media items passed in {@link MediaBrowserCompat.SubscriptionCallback#onChildrenLoaded(String, List)}
          * is considered ordered by relevance, first being the top suggestion.
          * If the media browser service can provide such media items, the implementation must return
          * the key in the root hint when {@link #onGetRoot(String, int, Bundle)} is called back.
          *
          * <p>The root hint may contain multiple keys.
          *
          * @see #EXTRA_RECENT
          * @see #EXTRA_OFFLINE
          */
         public static final String EXTRA_SUGGESTED = "android.service.media.extra.SUGGESTED";

         /**
          * The lookup key for a string that indicates specific keywords which will be considered
          * when the browser service suggests media items.
          *
          * <p>When creating a media browser for a given media browser service, this key can be
          * supplied as a root hint together with {@link #EXTRA_SUGGESTED} for retrieving suggested
          * media items related with the keywords. The list of media items passed in
          * {@link android.media.browse.MediaBrowser.SubscriptionCallback#onChildrenLoaded(String, List)}
          * is considered ordered by relevance, first being the top suggestion.
          * If the media browser service can provide such media items, the implementation must return
          * the key in the root hint when {@link #onGetRoot(String, int, Bundle)} is called back.
          *
          * <p>The root hint may contain multiple keys.
          *
          * @see #EXTRA_RECENT
          * @see #EXTRA_OFFLINE
          * @see #EXTRA_SUGGESTED
          * @deprecated The search functionality is now supported by the methods
          *             {@link MediaBrowserCompat#search} and {@link #onSearch}. Use those methods
          *             instead.
          */
         @Deprecated
         public static final String EXTRA_SUGGESTION_KEYWORDS
                 = "android.service.media.extra.SUGGESTION_KEYWORDS";

         final private String mRootId;
         final private Bundle mExtras;

         /**
          * Constructs a browser root.
          * @param rootId The root id for browsing.
          * @param extras Any extras about the browser service.
          */
         public BrowserRoot(@NonNull String rootId, @Nullable Bundle extras) {
             if (rootId == null) {
                 throw new IllegalArgumentException("The root id in BrowserRoot cannot be null. " +
                         "Use null for BrowserRoot instead");
             }
             mRootId = rootId;
             mExtras = extras;
         }

         /**
          * Gets the root id for browsing.
          */
         public String getRootId() {
             return mRootId;
         }

         /**
          * Gets any extras about the browser service.
          */
         public Bundle getExtras() {
             return mExtras;
         }
     }
 }