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/*
* Copyright (C) 2015 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.databinding.adapters;
import android.os.Build.VERSION;
import android.os.Build.VERSION_CODES;
import android.util.SparseArray;
import android.view.View;
import java.lang.ref.WeakReference;
import java.util.WeakHashMap;
public class ListenerUtil {
private static SparseArray<WeakHashMap<View, WeakReference<?>>> sListeners =
new SparseArray<>();
/**
* This method tracks listeners for a View. Only one listener per listenerResourceId
* can be tracked at a time. This is useful for add*Listener and remove*Listener methods
* when used with BindingAdapters. This guarantees not to leak the listener or the View,
* so will not keep a strong reference to either.
*
* Example usage:
* <pre>
* {@code
* @BindingAdapter("onFoo")
* public static void addFooListener(MyView view, OnFooListener listener) {
* OnFooListener oldValue = ListenerUtil.trackListener(view, listener, R.id.fooListener);
* if (oldValue != null) {
* view.removeOnFooListener(oldValue);
* }
* if (listener != null) {
* view.addOnFooListener(listener);
* }
* }
* }
* </pre>
*
* @param view The View that will have this listener
* @param listener The listener to keep track of. May be null if the listener is being removed.
* @param listenerResourceId A unique resource ID associated with the listener type.
* @return The previously tracked listener. This will be null if the View did not have
* a previously-tracked listener.
*/
@SuppressWarnings("unchecked")
public static <T> T trackListener(View view, T listener, int listenerResourceId) {
if (VERSION.SDK_INT >= VERSION_CODES.ICE_CREAM_SANDWICH) {
final T oldValue = (T) view.getTag(listenerResourceId);
view.setTag(listenerResourceId, listener);
return oldValue;
} else {
synchronized (sListeners) {
WeakHashMap<View, WeakReference<?>> listeners = sListeners.get(listenerResourceId);
if (listeners == null) {
listeners = new WeakHashMap<>();
sListeners.put(listenerResourceId, listeners);
}
final WeakReference<T> oldValue;
if (listener == null) {
oldValue = (WeakReference<T>) listeners.remove(view);
} else {
oldValue = (WeakReference<T>) listeners.put(view, new WeakReference(listener));
}
if (oldValue == null) {
return null;
} else {
return oldValue.get();
}
}
}
}
}
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