1 /* 2 * Copyright (C) 2015 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 package android.databinding.adapters; 17 18 import android.os.Build.VERSION; 19 import android.os.Build.VERSION_CODES; 20 import android.util.SparseArray; 21 import android.view.View; 22 23 import java.lang.ref.WeakReference; 24 import java.util.WeakHashMap; 25 26 public class ListenerUtil { 27 private static SparseArray<WeakHashMap<View, WeakReference<?>>> sListeners = 28 new SparseArray<WeakHashMap<View, WeakReference<?>>>(); 29 30 /** 31 * This method tracks listeners for a View. Only one listener per listenerResourceId 32 * can be tracked at a time. This is useful for add*Listener and remove*Listener methods 33 * when used with BindingAdapters. This guarantees not to leak the listener or the View, 34 * so will not keep a strong reference to either. 35 * 36 * Example usage: 37 *<pre><code>@BindingAdapter("onFoo") 38 * public static void addFooListener(MyView view, OnFooListener listener) { 39 * OnFooListener oldValue = ListenerUtil.trackListener(view, listener, R.id.fooListener); 40 * if (oldValue != null) { 41 * view.removeOnFooListener(oldValue); 42 * } 43 * if (listener != null) { 44 * view.addOnFooListener(listener); 45 * } 46 * }</code></pre> 47 * 48 * @param view The View that will have this listener 49 * @param listener The listener to keep track of. May be null if the listener is being removed. 50 * @param listenerResourceId A unique resource ID associated with the listener type. 51 * @return The previously tracked listener. This will be null if the View did not have 52 * a previously-tracked listener. 53 */ 54 @SuppressWarnings("unchecked") trackListener(View view, T listener, int listenerResourceId)55 public static <T> T trackListener(View view, T listener, int listenerResourceId) { 56 if (VERSION.SDK_INT >= VERSION_CODES.ICE_CREAM_SANDWICH) { 57 final T oldValue = (T) view.getTag(listenerResourceId); 58 view.setTag(listenerResourceId, listener); 59 return oldValue; 60 } else { 61 synchronized (sListeners) { 62 WeakHashMap<View, WeakReference<?>> listeners = sListeners.get(listenerResourceId); 63 if (listeners == null) { 64 listeners = new WeakHashMap<View, WeakReference<?>>(); 65 sListeners.put(listenerResourceId, listeners); 66 } 67 final WeakReference<T> oldValue; 68 if (listener == null) { 69 oldValue = (WeakReference<T>) listeners.remove(view); 70 } else { 71 oldValue = (WeakReference<T>) listeners.put(view, new WeakReference(listener)); 72 } 73 if (oldValue == null) { 74 return null; 75 } else { 76 return oldValue.get(); 77 } 78 } 79 } 80 } 81 82 /** 83 * Returns the previous value for a listener if one was stored previously with 84 * {@link #trackListener(View, Object, int)} 85 * @param view The View to check for a listener previously stored with 86 * {@link #trackListener(View, Object, int)} 87 * @param listenerResourceId A unique resource ID associated with the listener type. 88 * @return The previously tracked listener. This will be null if the View did not have 89 * a previously-tracked listener. 90 */ getListener(View view, int listenerResourceId)91 public static <T> T getListener(View view, int listenerResourceId) { 92 if (VERSION.SDK_INT >= VERSION_CODES.ICE_CREAM_SANDWICH) { 93 return (T) view.getTag(listenerResourceId); 94 } else { 95 synchronized (sListeners) { 96 WeakHashMap<View, WeakReference<?>> listeners = sListeners.get(listenerResourceId); 97 if (listeners == null) { 98 return null; 99 } 100 final WeakReference<T> oldValue = (WeakReference<T>) listeners.get(view); 101 if (oldValue == null) { 102 return null; 103 } else { 104 return oldValue.get(); 105 } 106 } 107 } 108 } 109 } 110