| /* |
| * Copyright (C) 2017 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 android.support.wear.widget.drawer; |
| |
| import android.os.Handler; |
| import android.os.Looper; |
| import android.support.annotation.RestrictTo; |
| import android.support.annotation.RestrictTo.Scope; |
| import android.support.v4.widget.NestedScrollView; |
| import android.support.v4.widget.NestedScrollView.OnScrollChangeListener; |
| import android.support.wear.widget.drawer.FlingWatcherFactory.FlingListener; |
| import android.support.wear.widget.drawer.FlingWatcherFactory.FlingWatcher; |
| import android.view.View; |
| |
| import java.lang.ref.WeakReference; |
| |
| /** |
| * {@link FlingWatcher} implementation for {@link NestedScrollView NestedScrollViews}. |
| * <p> |
| * Because {@link NestedScrollView} does not provide a way to listen to the scroll state, there's no |
| * callback which definitely indicates the fling has finished. So, we instead listen for scroll |
| * events. If we reach the top or bottom of the view or if there are no events within {@link |
| * #MAX_WAIT_TIME_MS}, we assume the fling has finished. |
| * |
| * @hide |
| */ |
| @RestrictTo(Scope.LIBRARY_GROUP) |
| class NestedScrollViewFlingWatcher implements FlingWatcher, OnScrollChangeListener { |
| |
| static final int MAX_WAIT_TIME_MS = 100; |
| private final Handler mMainThreadHandler = new Handler(Looper.getMainLooper()); |
| private final FlingListener mListener; |
| private final WeakReference<NestedScrollView> mNestedScrollView; |
| private final Runnable mNotifyListenerRunnable = new Runnable() { |
| @Override |
| public void run() { |
| onEndOfFlingFound(); |
| } |
| }; |
| |
| NestedScrollViewFlingWatcher(FlingListener listener, NestedScrollView nestedScrollView) { |
| mListener = listener; |
| mNestedScrollView = new WeakReference<>(nestedScrollView); |
| } |
| |
| private static boolean isViewAtTopOrBottom(View view) { |
| return !view.canScrollVertically(-1 /* up */) || !view.canScrollVertically(1 /* down */); |
| } |
| |
| @Override |
| public void watch() { |
| NestedScrollView nestedScrollView = mNestedScrollView.get(); |
| if (nestedScrollView != null) { |
| nestedScrollView.setOnScrollChangeListener(this); |
| scheduleNext(); |
| } |
| } |
| |
| @Override |
| public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, |
| int oldScrollY) { |
| if (isViewAtTopOrBottom(v)) { |
| onEndOfFlingFound(); |
| } else { |
| scheduleNext(); |
| } |
| } |
| |
| private void onEndOfFlingFound() { |
| mMainThreadHandler.removeCallbacks(mNotifyListenerRunnable); |
| NestedScrollView nestedScrollView = mNestedScrollView.get(); |
| if (nestedScrollView != null) { |
| nestedScrollView.setOnScrollChangeListener((OnScrollChangeListener) null); |
| mListener.onFlingComplete(nestedScrollView); |
| } |
| } |
| |
| private void scheduleNext() { |
| mMainThreadHandler.removeCallbacks(mNotifyListenerRunnable); |
| mMainThreadHandler.postDelayed(mNotifyListenerRunnable, MAX_WAIT_TIME_MS); |
| } |
| } |