fragment/fragment/src/main/java/androidx/fragment/app/FragmentContainerView.java - platform/frameworks/support - Git at Google

 /*
  * Copyright 2019 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.fragment.app;

 import android.animation.LayoutTransition;
 import android.content.Context;
 import android.content.res.TypedArray;
 import android.graphics.Canvas;
 import android.os.Build;
 import android.os.Bundle;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.WindowInsets;
 import android.widget.FrameLayout;

 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 import androidx.fragment.R;

 import java.util.ArrayList;
 /**
  * FragmentContainerView is a customized Layout designed specifically for Fragments. It extends
  * {@link FrameLayout}, so it can reliably handle Fragment Transactions, and it also has additional
  * features to coordinate with fragment behavior.
  *
  * <p>FragmentContainerView should be used as the container for Fragments, commonly set in the
  * xml layout of an activity, e.g.: <p>
  *
  * <pre class="prettyprint">
  * &lt;androidx.fragment.app.FragmentContainerView
  *        xmlns:android="http://schemas.android.com/apk/res/android"
  *        xmlns:app="http://schemas.android.com/apk/res-auto"
  *        android:id="@+id/fragment_container_view"
  *        android:layout_width="match_parent"
  *        android:layout_height="match_parent"&gt;
  * &lt;/androidx.fragment.app.FragmentContainerView&gt;
  * </pre>
  *
  * <p> FragmentContainerView can also be used to add a Fragment by using the
  * <code>android:name</code> attribute. FragmentContainerView will perform a one time operation
  * that:
  *
  * <ul>
  * <li>Creates a new instance of the Fragment</li>
  * <li>Calls {@link Fragment#onInflate(Context, AttributeSet, Bundle)}</li>
  * <li>Executes a FragmentTransaction to add the Fragment to the appropriate FragmentManager</li>
  * </ul>
  *
  * <p> You can optionally include an <code>android:tag</code> which allows you to use
  * {@link FragmentManager#findFragmentByTag(String)} to retrieve the added Fragment.
  *
  * <pre class="prettyprint">
  * &lt;androidx.fragment.app.FragmentContainerView
  *        xmlns:android="http://schemas.android.com/apk/res/android"
  *        xmlns:app="http://schemas.android.com/apk/res-auto"
  *        android:id="@+id/fragment_container_view"
  *        android:layout_width="match_parent"
  *        android:layout_height="match_parent"
  *        android:name="com.example.MyFragment"
  *        android:tag="my_tag"&gt;
  * &lt;/androidx.fragment.app.FragmentContainerView&gt;
  * </pre>
  *
  * <p>FragmentContainerView should not be used as a replacement for other ViewGroups (FrameLayout,
  * LinearLayout, etc) outside of Fragment use cases.
  *
  * <p>FragmentContainerView will only allow views returned by a Fragment's
  * {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any other
  * view will result in an {@link IllegalStateException}.
  *
  * <p>Layout animations and transitions are disabled for FragmentContainerView for APIs above 17.
  * Otherwise, Animations should be done through
  * {@link FragmentTransaction#setCustomAnimations(int, int, int, int)}. If animateLayoutChanges is
  * set to <code>true</code> or {@link #setLayoutTransition(LayoutTransition)} is called directly an
  * {@link UnsupportedOperationException} will be thrown.
  *
  * <p>Fragments using exit animations are drawn before all others for FragmentContainerView. This
  * ensures that exiting Fragments do not appear on top of the view.
  */
 public final class FragmentContainerView extends FrameLayout {

     private ArrayList<View> mDisappearingFragmentChildren;

     private ArrayList<View> mTransitioningFragmentViews;

     // Used to indicate whether the FragmentContainerView should override the default ViewGroup
     // drawing order.
     private boolean mDrawDisappearingViewsFirst = true;

     public FragmentContainerView(@NonNull Context context) {
         super(context);
     }

     /**
      * Do not call this constructor directly. Doing so will result in an
      * {@link UnsupportedOperationException}.
      */
     public FragmentContainerView(@NonNull Context context, @Nullable AttributeSet attrs) {
         this(context, attrs, 0);
     }

     /**
      * Do not call this constructor directly. Doing so will result in an
      * {@link UnsupportedOperationException}.
      */
     public FragmentContainerView(
             @NonNull Context context,
             @Nullable AttributeSet attrs,
             int defStyleAttr) {
         super(context, attrs, defStyleAttr);
         if (attrs != null) {
             String name = attrs.getClassAttribute();
             String attribute = "class";
             TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FragmentContainerView);
             if (name == null) {
                 name = a.getString(R.styleable.FragmentContainerView_android_name);
                 attribute = "android:name";
             }
             a.recycle();
             if (name != null && !isInEditMode()) {
                 throw new UnsupportedOperationException("FragmentContainerView must be within "
                         + "a FragmentActivity to use " + attribute + "=\"" + name + "\"");
             }
         }
     }

     FragmentContainerView(
             @NonNull Context context,
             @NonNull AttributeSet attrs,
             @NonNull FragmentManager fm) {
         super(context, attrs);

         String name = attrs.getClassAttribute();
         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FragmentContainerView);
         if (name == null) {
             name = a.getString(R.styleable.FragmentContainerView_android_name);
         }
         String tag = a.getString(R.styleable.FragmentContainerView_android_tag);
         a.recycle();

         int id = getId();
         Fragment existingFragment = fm.findFragmentById(id);
         // If there is a name and there is no existing fragment,
         // we should add an inflated Fragment to the view.
         if (name != null && existingFragment == null) {
             if (id <= 0) {
                 final String tagMessage = tag != null
                         ? " with tag " + tag
                         : "";
                 throw new IllegalStateException("FragmentContainerView must have an android:id to "
                         + "add Fragment " + name + tagMessage);
             }
             Fragment containerFragment =
                     fm.getFragmentFactory().instantiate(context.getClassLoader(), name);
             containerFragment.onInflate(context, attrs, null);
             fm.beginTransaction()
                     .setReorderingAllowed(true)
                     .add(this, containerFragment, tag)
                     .commitNowAllowingStateLoss();
         }
     }

     /**
      * When called, this method throws a {@link UnsupportedOperationException} on APIs above 17.
      * On APIs 17 and below, it calls {@link FrameLayout#setLayoutTransition(LayoutTransition)}
      * This can be called either explicitly, or implicitly by setting animateLayoutChanges to
      * <code>true</code>.
      *
      * <p>View animations and transitions are disabled for FragmentContainerView for APIs above 17.
      * Use {@link FragmentTransaction#setCustomAnimations(int, int, int, int)} and
      * {@link FragmentTransaction#setTransition(int)}.
      *
      * @param transition The LayoutTransition object that will animated changes in layout. A value
      * of <code>null</code> means no transition will run on layout changes.
      * @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
      */
     @Override
     public void setLayoutTransition(@Nullable LayoutTransition transition) {
         if (Build.VERSION.SDK_INT < 18) {
             // Transitions on APIs below 18 are using an empty LayoutTransition as a replacement
             // for suppressLayout(true) and null LayoutTransition to then unsuppress it. If the
             // API is below 18, we should allow FrameLayout to handle this call.
             super.setLayoutTransition(transition);
             return;
         }

         throw new UnsupportedOperationException(
                 "FragmentContainerView does not support Layout Transitions or "
                         + "animateLayoutChanges=\"true\".");
     }

     /**
      * {@inheritDoc}
      *
      * <p>The sys ui flags must be set to enable extending the layout into the window insets.
      */
     @NonNull
     @RequiresApi(20)
     @Override
     public WindowInsets onApplyWindowInsets(@NonNull WindowInsets insets) {
         for (int i = 0; i < getChildCount(); i++) {
             View child = getChildAt(i);
             // Give child views fresh insets.
             child.dispatchApplyWindowInsets(new WindowInsets(insets));
         }
         return insets;
     }

     @Override
     protected void dispatchDraw(@NonNull Canvas canvas) {
         if (mDrawDisappearingViewsFirst && mDisappearingFragmentChildren != null) {
             for (int i = 0; i < mDisappearingFragmentChildren.size(); i++) {
                 super.drawChild(canvas, mDisappearingFragmentChildren.get(i), getDrawingTime());
             }
         }
         super.dispatchDraw(canvas);
     }

     @Override
     protected boolean drawChild(@NonNull Canvas canvas, @NonNull View child, long drawingTime) {
         if (mDrawDisappearingViewsFirst && mDisappearingFragmentChildren != null
                 && mDisappearingFragmentChildren.size() > 0) {
             // If the child is disappearing, we have already drawn it so skip.
             if (mDisappearingFragmentChildren.contains(child)) {
                 return false;
             }
         }
         return super.drawChild(canvas, child, drawingTime);
     }

     @Override
     public void startViewTransition(@NonNull View view) {
         if (view.getParent() == this) {
             if (mTransitioningFragmentViews == null) {
                 mTransitioningFragmentViews = new ArrayList<>();
             }
             mTransitioningFragmentViews.add(view);
         }
         super.startViewTransition(view);
     }

     @Override
     public void endViewTransition(@NonNull View view) {
         if (mTransitioningFragmentViews != null) {
             mTransitioningFragmentViews.remove(view);
             if (mDisappearingFragmentChildren != null
                     && mDisappearingFragmentChildren.remove(view)) {
                 mDrawDisappearingViewsFirst = true;
             }
         }
         super.endViewTransition(view);
     }

     // Used to indicate the container should change the default drawing order.
     void setDrawDisappearingViewsLast(boolean drawDisappearingViewsFirst) {
         mDrawDisappearingViewsFirst = drawDisappearingViewsFirst;
     }

     /**
      * <p>FragmentContainerView will only allow views returned by a Fragment's
      * {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
      *  other view will result in an {@link IllegalStateException}.
      *
      * {@inheritDoc}
      */
     @Override
     public void addView(@NonNull View child, int index, @Nullable ViewGroup.LayoutParams params) {
         if (FragmentManager.getViewFragment(child) == null) {
             throw new IllegalStateException("Views added to a FragmentContainerView must be"
                     + " associated with a Fragment. View " + child + " is not associated with a"
                     + " Fragment.");
         }
         super.addView(child, index, params);
     }

     /**
      * <p>FragmentContainerView will only allow views returned by a Fragment's
      * {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
      *  other view will result in an {@link IllegalStateException}.
      *
      * {@inheritDoc}
      */
     @Override
     protected boolean addViewInLayout(@NonNull View child, int index,
             @Nullable ViewGroup.LayoutParams params, boolean preventRequestLayout) {
         if (FragmentManager.getViewFragment(child) == null) {
             throw new IllegalStateException("Views added to a FragmentContainerView must be"
                     + " associated with a Fragment. View " + child + " is not associated with a"
                     + " Fragment.");
         }
         return super.addViewInLayout(child, index, params, preventRequestLayout);
     }

     @Override
     public void removeViewAt(int index) {
         View view = getChildAt(index);
         addDisappearingFragmentView(view);
         super.removeViewAt(index);
     }

     @Override
     public void removeViewInLayout(@NonNull View view) {
         addDisappearingFragmentView(view);
         super.removeViewInLayout(view);
     }

     @Override
     public void removeView(@NonNull View view) {
         addDisappearingFragmentView(view);
         super.removeView(view);
     }

     @Override
     public void removeViews(int start, int count) {
         for (int i = start; i < start + count; i++) {
             final View view = getChildAt(i);
             addDisappearingFragmentView(view);
         }
         super.removeViews(start, count);
     }

     @Override
     public void removeViewsInLayout(int start, int count) {
         for (int i = start; i < start + count; i++) {
             final View view = getChildAt(i);
             addDisappearingFragmentView(view);
         }
         super.removeViewsInLayout(start, count);
     }

     @Override
     public void removeAllViewsInLayout() {
         for (int i = getChildCount() - 1; i >= 0; i--) {
             final View view = getChildAt(i);
             addDisappearingFragmentView(view);
         }
         super.removeAllViewsInLayout();
     }

     @Override
     protected void removeDetachedView(@NonNull View child, boolean animate) {
         if (animate) {
             addDisappearingFragmentView(child);
         }
         super.removeDetachedView(child, animate);
     }

     /**
      * This method adds a {@link View} to the list of disappearing views only if it meets the
      * proper conditions to be considered a disappearing view.
      *
      * @param v {@link View} that might be added to list of disappearing views
      */
     private void addDisappearingFragmentView(@NonNull View v) {
         if (mTransitioningFragmentViews != null && mTransitioningFragmentViews.contains(v)) {
             if (mDisappearingFragmentChildren == null) {
                 mDisappearingFragmentChildren = new ArrayList<>();
             }
             mDisappearingFragmentChildren.add(v);
         }
     }
 }
	/*
	* Copyright 2019 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.fragment.app;

	import android.animation.LayoutTransition;
	import android.content.Context;
	import android.content.res.TypedArray;
	import android.graphics.Canvas;
	import android.os.Build;
	import android.os.Bundle;
	import android.util.AttributeSet;
	import android.view.LayoutInflater;
	import android.view.View;
	import android.view.ViewGroup;
	import android.view.WindowInsets;
	import android.widget.FrameLayout;

	import androidx.annotation.NonNull;
	import androidx.annotation.Nullable;
	import androidx.annotation.RequiresApi;
	import androidx.fragment.R;

	import java.util.ArrayList;
	/**
	* FragmentContainerView is a customized Layout designed specifically for Fragments. It extends
	* {@link FrameLayout}, so it can reliably handle Fragment Transactions, and it also has additional
	* features to coordinate with fragment behavior.
	*
	* <p>FragmentContainerView should be used as the container for Fragments, commonly set in the
	* xml layout of an activity, e.g.: <p>
	*
	* <pre class="prettyprint">
	* <androidx.fragment.app.FragmentContainerView
	* xmlns:android="http://schemas.android.com/apk/res/android"
	* xmlns:app="http://schemas.android.com/apk/res-auto"
	* android:id="@+id/fragment_container_view"
	* android:layout_width="match_parent"
	* android:layout_height="match_parent">
	* </androidx.fragment.app.FragmentContainerView>
	* </pre>
	*
	* <p> FragmentContainerView can also be used to add a Fragment by using the
	* <code>android:name</code> attribute. FragmentContainerView will perform a one time operation
	* that:
	*
	* <ul>
	* <li>Creates a new instance of the Fragment</li>
	* <li>Calls {@link Fragment#onInflate(Context, AttributeSet, Bundle)}</li>
	* <li>Executes a FragmentTransaction to add the Fragment to the appropriate FragmentManager</li>
	* </ul>
	*
	* <p> You can optionally include an <code>android:tag</code> which allows you to use
	* {@link FragmentManager#findFragmentByTag(String)} to retrieve the added Fragment.
	*
	* <pre class="prettyprint">
	* <androidx.fragment.app.FragmentContainerView
	* xmlns:android="http://schemas.android.com/apk/res/android"
	* xmlns:app="http://schemas.android.com/apk/res-auto"
	* android:id="@+id/fragment_container_view"
	* android:layout_width="match_parent"
	* android:layout_height="match_parent"
	* android:name="com.example.MyFragment"
	* android:tag="my_tag">
	* </androidx.fragment.app.FragmentContainerView>
	* </pre>
	*
	* <p>FragmentContainerView should not be used as a replacement for other ViewGroups (FrameLayout,
	* LinearLayout, etc) outside of Fragment use cases.
	*
	* <p>FragmentContainerView will only allow views returned by a Fragment's
	* {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any other
	* view will result in an {@link IllegalStateException}.
	*
	* <p>Layout animations and transitions are disabled for FragmentContainerView for APIs above 17.
	* Otherwise, Animations should be done through
	* {@link FragmentTransaction#setCustomAnimations(int, int, int, int)}. If animateLayoutChanges is
	* set to <code>true</code> or {@link #setLayoutTransition(LayoutTransition)} is called directly an
	* {@link UnsupportedOperationException} will be thrown.
	*
	* <p>Fragments using exit animations are drawn before all others for FragmentContainerView. This
	* ensures that exiting Fragments do not appear on top of the view.
	*/
	public final class FragmentContainerView extends FrameLayout {

	private ArrayList<View> mDisappearingFragmentChildren;

	private ArrayList<View> mTransitioningFragmentViews;

	// Used to indicate whether the FragmentContainerView should override the default ViewGroup
	// drawing order.
	private boolean mDrawDisappearingViewsFirst = true;

	public FragmentContainerView(@NonNull Context context) {
	super(context);
	}

	/**
	* Do not call this constructor directly. Doing so will result in an
	* {@link UnsupportedOperationException}.
	*/
	public FragmentContainerView(@NonNull Context context, @Nullable AttributeSet attrs) {
	this(context, attrs, 0);
	}

	/**
	* Do not call this constructor directly. Doing so will result in an
	* {@link UnsupportedOperationException}.
	*/
	public FragmentContainerView(
	@NonNull Context context,
	@Nullable AttributeSet attrs,
	int defStyleAttr) {
	super(context, attrs, defStyleAttr);
	if (attrs != null) {
	String name = attrs.getClassAttribute();
	String attribute = "class";
	TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FragmentContainerView);
	if (name == null) {
	name = a.getString(R.styleable.FragmentContainerView_android_name);
	attribute = "android:name";
	}
	a.recycle();
	if (name != null && !isInEditMode()) {
	throw new UnsupportedOperationException("FragmentContainerView must be within "
	+ "a FragmentActivity to use " + attribute + "=\"" + name + "\"");
	}
	}
	}

	FragmentContainerView(
	@NonNull Context context,
	@NonNull AttributeSet attrs,
	@NonNull FragmentManager fm) {
	super(context, attrs);

	String name = attrs.getClassAttribute();
	TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.FragmentContainerView);
	if (name == null) {
	name = a.getString(R.styleable.FragmentContainerView_android_name);
	}
	String tag = a.getString(R.styleable.FragmentContainerView_android_tag);
	a.recycle();

	int id = getId();
	Fragment existingFragment = fm.findFragmentById(id);
	// If there is a name and there is no existing fragment,
	// we should add an inflated Fragment to the view.
	if (name != null && existingFragment == null) {
	if (id <= 0) {
	final String tagMessage = tag != null
	? " with tag " + tag
	: "";
	throw new IllegalStateException("FragmentContainerView must have an android:id to "
	+ "add Fragment " + name + tagMessage);
	}
	Fragment containerFragment =
	fm.getFragmentFactory().instantiate(context.getClassLoader(), name);
	containerFragment.onInflate(context, attrs, null);
	fm.beginTransaction()
	.setReorderingAllowed(true)
	.add(this, containerFragment, tag)
	.commitNowAllowingStateLoss();
	}
	}

	/**
	* When called, this method throws a {@link UnsupportedOperationException} on APIs above 17.
	* On APIs 17 and below, it calls {@link FrameLayout#setLayoutTransition(LayoutTransition)}
	* This can be called either explicitly, or implicitly by setting animateLayoutChanges to
	* <code>true</code>.
	*
	* <p>View animations and transitions are disabled for FragmentContainerView for APIs above 17.
	* Use {@link FragmentTransaction#setCustomAnimations(int, int, int, int)} and
	* {@link FragmentTransaction#setTransition(int)}.
	*
	* @param transition The LayoutTransition object that will animated changes in layout. A value
	* of <code>null</code> means no transition will run on layout changes.
	* @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
	*/
	@Override
	public void setLayoutTransition(@Nullable LayoutTransition transition) {
	if (Build.VERSION.SDK_INT < 18) {
	// Transitions on APIs below 18 are using an empty LayoutTransition as a replacement
	// for suppressLayout(true) and null LayoutTransition to then unsuppress it. If the
	// API is below 18, we should allow FrameLayout to handle this call.
	super.setLayoutTransition(transition);
	return;
	}

	throw new UnsupportedOperationException(
	"FragmentContainerView does not support Layout Transitions or "
	+ "animateLayoutChanges=\"true\".");
	}

	/**
	* {@inheritDoc}
	*
	* <p>The sys ui flags must be set to enable extending the layout into the window insets.
	*/
	@NonNull
	@RequiresApi(20)
	@Override
	public WindowInsets onApplyWindowInsets(@NonNull WindowInsets insets) {
	for (int i = 0; i < getChildCount(); i++) {
	View child = getChildAt(i);
	// Give child views fresh insets.
	child.dispatchApplyWindowInsets(new WindowInsets(insets));
	}
	return insets;
	}

	@Override
	protected void dispatchDraw(@NonNull Canvas canvas) {
	if (mDrawDisappearingViewsFirst && mDisappearingFragmentChildren != null) {
	for (int i = 0; i < mDisappearingFragmentChildren.size(); i++) {
	super.drawChild(canvas, mDisappearingFragmentChildren.get(i), getDrawingTime());
	}
	}
	super.dispatchDraw(canvas);
	}

	@Override
	protected boolean drawChild(@NonNull Canvas canvas, @NonNull View child, long drawingTime) {
	if (mDrawDisappearingViewsFirst && mDisappearingFragmentChildren != null
	&& mDisappearingFragmentChildren.size() > 0) {
	// If the child is disappearing, we have already drawn it so skip.
	if (mDisappearingFragmentChildren.contains(child)) {
	return false;
	}
	}
	return super.drawChild(canvas, child, drawingTime);
	}

	@Override
	public void startViewTransition(@NonNull View view) {
	if (view.getParent() == this) {
	if (mTransitioningFragmentViews == null) {
	mTransitioningFragmentViews = new ArrayList<>();
	}
	mTransitioningFragmentViews.add(view);
	}
	super.startViewTransition(view);
	}

	@Override
	public void endViewTransition(@NonNull View view) {
	if (mTransitioningFragmentViews != null) {
	mTransitioningFragmentViews.remove(view);
	if (mDisappearingFragmentChildren != null
	&& mDisappearingFragmentChildren.remove(view)) {
	mDrawDisappearingViewsFirst = true;
	}
	}
	super.endViewTransition(view);
	}

	// Used to indicate the container should change the default drawing order.
	void setDrawDisappearingViewsLast(boolean drawDisappearingViewsFirst) {
	mDrawDisappearingViewsFirst = drawDisappearingViewsFirst;
	}

	/**
	* <p>FragmentContainerView will only allow views returned by a Fragment's
	* {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
	* other view will result in an {@link IllegalStateException}.
	*
	* {@inheritDoc}
	*/
	@Override
	public void addView(@NonNull View child, int index, @Nullable ViewGroup.LayoutParams params) {
	if (FragmentManager.getViewFragment(child) == null) {
	throw new IllegalStateException("Views added to a FragmentContainerView must be"
	+ " associated with a Fragment. View " + child + " is not associated with a"
	+ " Fragment.");
	}
	super.addView(child, index, params);
	}

	/**
	* <p>FragmentContainerView will only allow views returned by a Fragment's
	* {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
	* other view will result in an {@link IllegalStateException}.
	*
	* {@inheritDoc}
	*/
	@Override
	protected boolean addViewInLayout(@NonNull View child, int index,
	@Nullable ViewGroup.LayoutParams params, boolean preventRequestLayout) {
	if (FragmentManager.getViewFragment(child) == null) {
	throw new IllegalStateException("Views added to a FragmentContainerView must be"
	+ " associated with a Fragment. View " + child + " is not associated with a"
	+ " Fragment.");
	}
	return super.addViewInLayout(child, index, params, preventRequestLayout);
	}

	@Override
	public void removeViewAt(int index) {
	View view = getChildAt(index);
	addDisappearingFragmentView(view);
	super.removeViewAt(index);
	}

	@Override
	public void removeViewInLayout(@NonNull View view) {
	addDisappearingFragmentView(view);
	super.removeViewInLayout(view);
	}

	@Override
	public void removeView(@NonNull View view) {
	addDisappearingFragmentView(view);
	super.removeView(view);
	}

	@Override
	public void removeViews(int start, int count) {
	for (int i = start; i < start + count; i++) {
	final View view = getChildAt(i);
	addDisappearingFragmentView(view);
	}
	super.removeViews(start, count);
	}

	@Override
	public void removeViewsInLayout(int start, int count) {
	for (int i = start; i < start + count; i++) {
	final View view = getChildAt(i);
	addDisappearingFragmentView(view);
	}
	super.removeViewsInLayout(start, count);
	}

	@Override
	public void removeAllViewsInLayout() {
	for (int i = getChildCount() - 1; i >= 0; i--) {
	final View view = getChildAt(i);
	addDisappearingFragmentView(view);
	}
	super.removeAllViewsInLayout();
	}

	@Override
	protected void removeDetachedView(@NonNull View child, boolean animate) {
	if (animate) {
	addDisappearingFragmentView(child);
	}
	super.removeDetachedView(child, animate);
	}

	/**
	* This method adds a {@link View} to the list of disappearing views only if it meets the
	* proper conditions to be considered a disappearing view.
	*
	* @param v {@link View} that might be added to list of disappearing views
	*/
	private void addDisappearingFragmentView(@NonNull View v) {
	if (mTransitioningFragmentViews != null && mTransitioningFragmentViews.contains(v)) {
	if (mDisappearingFragmentChildren == null) {
	mDisappearingFragmentChildren = new ArrayList<>();
	}
	mDisappearingFragmentChildren.add(v);
	}
	}
	}