Android Handler内存泄漏

1. 原因分析

1.1 内存泄漏实例

首先看一个简单的Handler引发内存泄漏的例子：

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, );
    }

}
           

1.2 内存泄漏分析

Handler的引用阻止GC回收Activity

• 在Java中，非静态(匿名)内部类会默认隐性引用外部类对象。

  如果外部类是Activity就会造成内存泄漏

• Handler和Activity的生命周期不一致

  就上面的例子而言，当Activity结束后，消息循环中还有延时消息，那么Handler还会一直存在，知道所有消息处理完，但Handler引用了Activity，那么就会阻止Activity被回收，造成内存泄漏。

2. 解决方式

（1）使用显式引用

• 把Handler声明为静态内部类，而静态内部类不会引用外部类对象
• 把Handler声明为静态外部类

（2）在handler中弱引用Activity

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

    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() {

    }
}