Android Handler內存泄漏

1. 原因分析

1.1 內存泄漏實例

首先看一個簡單的Handler引發內存泄漏的例子：

public class HandlerActivity extends Activity {

    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case Const.NOTIFY_LOCATION_SUC:
                    boolean isSuc = (Boolean) msg.obj;
                    doLocation(isSuc);
                    break;

                default:
                    break;
            }
            super.handleMessage(msg);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        initView();

 mHandler.sendEmptyMessageDelayed(Const.NOTIFY_LOCATION_SUC, 10000);
    }

}

1.2 內存泄漏分析

Handler的引用阻止GC回收Activity

• 在Java中，非靜態(匿名)內部類會默認隱性引用外部類對象。
  如果外部類是Activity就會造成內存泄漏

• Handler和Activity的生命週期不一致
  就上面的例子而言，當Activity結束後，消息循環中還有延時消息，那麼Handler還會一直存在，知道所有消息處理完，但Handler引用了Activity，那麼就會阻止Activity被回收，造成內存泄漏。

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2. 解決方式

（1）使用顯式引用

• 把Handler聲明爲靜態內部類，而靜態內部類不會引用外部類對象
• 把Handler聲明爲靜態外部類

（2）在handler中弱引用Activity

public class HandlerActivity extends Activity {
    private static final int MSG_START_RECORDING = 0x1001;
    private static final int MSG_STOP_RECORDING = 0x1002;

    private WorkHandler mHandler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mHandler = new WorkHandler(this);
    }

    public void start() {
        mHandler.sendMessage(mHandler.obtainMessage(MSG_START_RECORDING));
    }

    public void stop() {
        mHandler.sendMessage(mHandler.obtainMessage(MSG_STOP_RECORDING));
    }

    private static class WorkHandler extends Handler {
        private WeakReference<HandlerActivity> mWeakActivity;

        public WorkHandler(HandlerActivity activity) {
            super();
            mWeakActivity = new WeakReference<HandlerActivity>(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

            HandlerActivity activity = mWeakActivity.get();

            switch (msg.what) {
                case MSG_START_RECORDING:
                    activity.handleStartEncoding();
                    break;

                case MSG_STOP_RECORDING:
                    activity.handleStopEncoding();
                    break;
            }
        }
    }

    private void handleStartEncoding() {

    }

    private void handleStopEncoding() {

    }
}