| /* |
| * Copyright (C) 2016 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.core.widget; |
| |
| import android.os.Build; |
| import android.view.View; |
| import android.widget.ListView; |
| |
| import androidx.annotation.DoNotInline; |
| import androidx.annotation.NonNull; |
| import androidx.annotation.RequiresApi; |
| |
| /** |
| * Helper for accessing features in {@link ListView} |
| */ |
| public final class ListViewCompat { |
| |
| /** |
| * Scrolls the list items within the view by a specified number of pixels. |
| * |
| * @param listView the list to scroll |
| * @param y the amount of pixels to scroll by vertically |
| */ |
| public static void scrollListBy(@NonNull ListView listView, int y) { |
| if (Build.VERSION.SDK_INT >= 19) { |
| // Call the framework version directly |
| Api19Impl.scrollListBy(listView, y); |
| } else { |
| // provide backport on earlier versions |
| final int firstPosition = listView.getFirstVisiblePosition(); |
| if (firstPosition == ListView.INVALID_POSITION) { |
| return; |
| } |
| |
| final View firstView = listView.getChildAt(0); |
| if (firstView == null) { |
| return; |
| } |
| |
| final int newTop = firstView.getTop() - y; |
| listView.setSelectionFromTop(firstPosition, newTop); |
| } |
| } |
| |
| /** |
| * Check if the items in the list can be scrolled in a certain direction. |
| * |
| * @param listView ListView for which to check the state. |
| * @param direction Negative to check scrolling up, positive to check |
| * scrolling down. |
| * @return true if the list can be scrolled in the specified direction, |
| * false otherwise. |
| * @see #scrollListBy(ListView, int) |
| */ |
| public static boolean canScrollList(@NonNull ListView listView, int direction) { |
| if (Build.VERSION.SDK_INT >= 19) { |
| // Call the framework version directly |
| return Api19Impl.canScrollList(listView, direction); |
| } else { |
| // provide backport on earlier versions |
| final int childCount = listView.getChildCount(); |
| if (childCount == 0) { |
| return false; |
| } |
| |
| final int firstPosition = listView.getFirstVisiblePosition(); |
| if (direction > 0) { |
| final int lastBottom = listView.getChildAt(childCount - 1).getBottom(); |
| final int lastPosition = firstPosition + childCount; |
| return lastPosition < listView.getCount() |
| || (lastBottom > listView.getHeight() - listView.getListPaddingBottom()); |
| } else { |
| final int firstTop = listView.getChildAt(0).getTop(); |
| return firstPosition > 0 || firstTop < listView.getListPaddingTop(); |
| } |
| } |
| } |
| |
| private ListViewCompat() { |
| } |
| |
| @RequiresApi(19) |
| static class Api19Impl { |
| private Api19Impl() { |
| // This class is not instantiable. |
| } |
| |
| @DoNotInline |
| static void scrollListBy(ListView absListView, int y) { |
| absListView.scrollListBy(y); |
| } |
| |
| @DoNotInline |
| static boolean canScrollList(ListView absListView, int direction) { |
| return absListView.canScrollList(direction); |
| } |
| } |
| } |