常用handler导致内存泄露

public class  extends Activity {

    private MyHandler mMyHandler;

    
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mMyHandler = new MyHandler(this);
        mMyHandler.sendEmptyMessage(0);
    }


    private static class MyHandler extends Handler {
        private SoftReference<MainActivity> mActivity = null;

        public MyHandler(MainActivity mainActivity) {
            mActivity = new SoftReference<MainActivity>(mainActivity);
        }

        
        public void handleMessage(Message msg) {
            System.out.println(msg);
            if (mActivity.get() == null) {
                return;
            }
            mActivity.get().todo();
        }
    }

    
    protected void onDestroy() {
        super.onDestroy();
        mMyHandler.removeCallbacksAndMessages(null);
    }

    protected void todo() {
        Toast.makeText(this, "haha", Toast.LENGTH_SHORT).show();
    }
}