Hanlder ＋ 弱引用防内存漏泄示例＊

Hanlder ＋ 弱引用防内存漏泄示例：

public class MainActivity extends AppCompatActivity {

    public final MyHandler handler = new MyHandler(this);
    public final ThreadA threadA = new ThreadA(this);

    public static class ThreadA extends Thread {
        private WeakReference<MainActivity> activityRef;

        public ThreadA(MainActivity activity) {
            activityRef = new WeakReference<MainActivity>(activity);
        }

        @Override
        public void run() {
            MainActivity activity = activityRef.get();
            if (activity != null) {
                Message msg = new Message();
                msg.obj = "Hi,MainThread, I'm threadA.";
                activity.handler.sendMessage(msg);
            }
        }
    }

    ;

    public static class MyHandler extends Handler {

        private WeakReference<MainActivity> activityRef;

        public MyHandler(MainActivity activity) {
            activityRef = new WeakReference<MainActivity>(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            MainActivity activity = activityRef.get();
            if (activity != null) {
                //...
                String data = (String) msg.obj;
                System.out.println(data);
            }
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        System.out.println("onCreate");
        //...

        threadA.start();//开启一个无内存泄漏的线程（对MainActivity 弱引用），

        //...
    }

}