1/*
2 * Copyright (C) 2017 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.support.wear.widget.drawer;
18
19import android.support.annotation.RestrictTo;
20import android.support.annotation.RestrictTo.Scope;
21import android.support.v7.widget.RecyclerView;
22import android.support.v7.widget.RecyclerView.OnScrollListener;
23import android.support.wear.widget.drawer.FlingWatcherFactory.FlingListener;
24import android.support.wear.widget.drawer.FlingWatcherFactory.FlingWatcher;
25
26import java.lang.ref.WeakReference;
27
28/**
29 * {@link FlingWatcher} implementation for {@link RecyclerView RecyclerViews}. Detects the end of
30 * a Fling by waiting until the scroll state becomes idle.
31 *
32 * @hide
33 */
34@RestrictTo(Scope.LIBRARY_GROUP)
35class RecyclerViewFlingWatcher extends OnScrollListener implements FlingWatcher {
36
37    private final FlingListener mListener;
38    private final WeakReference<RecyclerView> mRecyclerView;
39
40    RecyclerViewFlingWatcher(FlingListener listener, RecyclerView view) {
41        mListener = listener;
42        mRecyclerView = new WeakReference<>(view);
43    }
44
45    @Override
46    public void watch() {
47        RecyclerView recyclerView = mRecyclerView.get();
48        if (recyclerView != null) {
49            recyclerView.addOnScrollListener(this);
50        }
51    }
52
53    @Override
54    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
55        if (newState == RecyclerView.SCROLL_STATE_IDLE) {
56            mListener.onFlingComplete(recyclerView);
57            recyclerView.removeOnScrollListener(this);
58        }
59    }
60}
61