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），

         //...
     }

 }