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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 com.android.tv.common;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.support.annotation.NonNull;
import java.lang.ref.WeakReference;
/**
* A Handler that keeps a {@link WeakReference} to an object.
*
* <p>Use this to prevent leaking an Activity or other Context while messages are still pending.
* When you extend this class you <strong>MUST NOT</strong> use a non static inner class, or the
* containing object will still be leaked.
*
* <p>See <a href="http://android-developers.blogspot.com/2009/01/avoiding-memory-leaks.html">
* Avoiding memory leaks</a>.
*/
public abstract class WeakHandler<T> extends Handler {
private final WeakReference<T> mRef;
/**
* Constructs a new handler with a weak reference to the given referent using the provided
* Looper instead of the default one.
*
* @param looper The looper, must not be null.
* @param ref the referent to track
*/
public WeakHandler(@NonNull Looper looper, T ref) {
super(looper);
mRef = new WeakReference<>(ref);
}
/**
* Constructs a new handler with a weak reference to the given referent.
*
* @param ref the referent to track
*/
public WeakHandler(T ref) {
mRef = new WeakReference<>(ref);
}
/** Calls {@link #handleMessage(Message, Object)} if the WeakReference is not cleared. */
@Override
public final void handleMessage(Message msg) {
T referent = mRef.get();
if (referent == null) {
return;
}
handleMessage(msg, referent);
}
/**
* Subclasses must implement this to receive messages.
*
* <p>If the WeakReference is cleared this method will no longer be called.
*
* @param msg the message to handle
* @param referent the referent. Guaranteed to be non null.
*/
protected abstract void handleMessage(Message msg, @NonNull T referent);
}
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