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      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 
     17 package androidx.wear.widget.drawer;
     18 
     19 import android.view.View;
     20 import android.widget.AbsListView;
     21 import android.widget.ScrollView;
     22 
     23 import androidx.annotation.Nullable;
     24 import androidx.annotation.RestrictTo;
     25 import androidx.annotation.RestrictTo.Scope;
     26 import androidx.core.widget.NestedScrollView;
     27 import androidx.recyclerview.widget.RecyclerView;
     28 
     29 import java.util.Map;
     30 import java.util.WeakHashMap;
     31 
     32 /**
     33  * Creates a {@link FlingWatcher} based on the type of {@link View}.
     34  *
     35  * @hide
     36  */
     37 @RestrictTo(Scope.LIBRARY)
     38 class FlingWatcherFactory {
     39 
     40     /**
     41      * Listener that is notified when a fling completes and the view has settled. Polling may be
     42      * used to determine when the fling has completed, so there may be up to a 100ms delay.
     43      */
     44     interface FlingListener {
     45         void onFlingComplete(View view);
     46     }
     47 
     48     /**
     49      * Watches a given {@code view} to detect the end of a fling. Will notify a {@link
     50      * FlingListener} when the end is found.
     51      */
     52     interface FlingWatcher {
     53         void watch();
     54     }
     55 
     56     private final FlingListener mListener;
     57     private final Map<View, FlingWatcher> mWatchers = new WeakHashMap<>();
     58 
     59     FlingWatcherFactory(FlingListener listener) {
     60         if (listener == null) {
     61             throw new IllegalArgumentException("FlingListener was null");
     62         }
     63 
     64         mListener = listener;
     65     }
     66 
     67     /**
     68      * Returns a {@link FlingWatcher} for the particular type of {@link View}.
     69      */
     70     @Nullable
     71     FlingWatcher getFor(View view) {
     72         FlingWatcher watcher = mWatchers.get(view);
     73         if (watcher == null) {
     74             watcher = createFor(view);
     75             if (watcher != null) {
     76                 mWatchers.put(view, watcher);
     77             }
     78         }
     79 
     80         return watcher;
     81     }
     82 
     83     /**
     84      * Creates a {@link FlingWatcher} for the particular type of {@link View}.
     85      */
     86     @Nullable
     87     private FlingWatcher createFor(View view) {
     88         if (view == null) {
     89             throw new IllegalArgumentException("View was null");
     90         }
     91 
     92         if (view instanceof RecyclerView) {
     93             return new RecyclerViewFlingWatcher(mListener, (RecyclerView) view);
     94         } else if (view instanceof AbsListView) {
     95             return new AbsListViewFlingWatcher(mListener, (AbsListView) view);
     96         } else if (view instanceof ScrollView) {
     97             return new ScrollViewFlingWatcher(mListener, (ScrollView) view);
     98         } else if (view instanceof NestedScrollView) {
     99             return new NestedScrollViewFlingWatcher(mListener, (NestedScrollView) view);
    100         } else {
    101             return null;
    102         }
    103     }
    104 }
    105