Handler防泄漏的正确使用姿势

某年某月某日在VLC的库源码里面看到的，总结一下

public class WeakHandler<T extends WeakHandler.MessageListener> extends Handler {
    private final WeakReference<T> mHandlerReference;

    public WeakHandler(T owner) {
        mHandlerReference = new WeakReference<>(owner);
    }


    @Override
    public void handleMessage(Message msg) {
        final T owner = getOwner();
        if (owner != null) {
            owner.handleMessage(msg);
        }
    }

    public interface MessageListener {
        public void handleMessage(Message msg);
    }

    public T getOwner() {
        return this.mHandlerReference.get();
    }

    public void clear() {
        mHandlerReference.clear();
    }
}

在activity里面使用

public class HandlerActivity extends Activity implements MyWeakHandler.MessageListener {

    private static MyWeakHandler<HandlerActivity> sHandler;//设置成静态成员，否则会出现内存泄漏
    public static final int MSG_ON_A = 0x111;
    public static final int MSG_ON_B = 0x112;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        sHandler = new MyWeakHandler<>(this);
    }


    @Override
    protected void onDestroy() {
        super.onDestroy();
        sHandler.removeCallbacksAndMessages(null);//清除所有未处理的消息
        sHandler.clear();
        sHandler=null;
    }

    private void backgroundWorkA() {

        .....
        //耗时操作,一般在线程的run方法或者Android系统框架回调放方法,比如低功耗蓝牙 BluetoothAdapter.LeScanCallback的 onLeScan()回调方法
        sHandler.obtainMessage(MSG_ON_A).sendToTarget();
        .....
    }

    private void backgroundWorkB() {

        ....
        //耗时操作
        sHandler.obtainMessage(MSG_ON_B).sendToTarget();
        .....
    }

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) { //处理各种消息
            case MSG_ON_A:
                break;
            case MSG_ON_B:
                break;
        }

    }
}