这个Handler类应该是静态的，否则可能会发生泄漏

我正在开发一个带有服务的Android 2.3.3应用程序。我在这个服务中有这个来与Main活动通信:

public class UDPListenerService extends Service
{
    private static final String TAG = "UDPListenerService";
    //private ThreadGroup myThreads = new ThreadGroup("UDPListenerServiceWorker");
    private UDPListenerThread myThread;
    /**
     * Handler to communicate from WorkerThread to service.
     */
    private Handler mServiceHandler;

    // Used to receive messages from the Activity
    final Messenger inMessenger = new Messenger(new IncomingHandler());
    // Use to send message to the Activity
    private Messenger outMessenger;

    class IncomingHandler extends Handler
    {
        @Override
        public void handleMessage(Message msg)
        {
        }
    }

    /**
     * Target we publish for clients to send messages to Incoming Handler.
     */
    final Messenger mMessenger = new Messenger(new IncomingHandler());
    [ ... ]
}

在这里，final Messenger mMessenger = new Messenger(new IncomingHandler());，我得到以下Lint警告:

这是什么意思?

当前回答

这种方法对我来说很有效，通过将处理消息的位置保留在它自己的内部类中，从而保持代码干净。

您希望使用的处理程序

Handler mIncomingHandler = new Handler(new IncomingHandlerCallback());

内部类

class IncomingHandlerCallback implements Handler.Callback{

        @Override
        public boolean handleMessage(Message message) {

            // Handle message code

            return true;
        }
}

2013-04-17 23:16:47

其他回答

我不确定，但你可以尝试初始化处理程序为空在onDestroy()

2015-01-07 09:25:08

下面是一个使用弱引用和静态处理程序类来解决问题的通用示例(在Lint文档中推荐):

public class MyClass{

  //static inner class doesn't hold an implicit reference to the outer class
  private static class MyHandler extends Handler {
    //Using a weak reference means you won't prevent garbage collection
    private final WeakReference<MyClass> myClassWeakReference; 

    public MyHandler(MyClass myClassInstance) {
      myClassWeakReference = new WeakReference<MyClass>(myClassInstance);
    }

    @Override
    public void handleMessage(Message msg) {
      MyClass myClass = myClassWeakReference.get();
      if (myClass != null) {
        ...do work here...
      }
    }
  }

  /**
   * An example getter to provide it to some external class
   * or just use 'new MyHandler(this)' if you are using it internally.
   * If you only use it internally you might even want it as final member:
   * private final MyHandler mHandler = new MyHandler(this);
   */
  public Handler getHandler() {
    return new MyHandler(this);
  }
}

2015-01-07 18:25:07

这种方法对我来说很有效，通过将处理消息的位置保留在它自己的内部类中，从而保持代码干净。

您希望使用的处理程序

Handler mIncomingHandler = new Handler(new IncomingHandlerCallback());

内部类

class IncomingHandlerCallback implements Handler.Callback{

        @Override
        public boolean handleMessage(Message message) {

            // Handle message code

            return true;
        }
}

2013-04-17 23:16:47

借助@Sogger的回答，我创建了一个通用的Handler:

public class MainThreadHandler<T extends MessageHandler> extends Handler {

    private final WeakReference<T> mInstance;

    public MainThreadHandler(T clazz) {
        // Remove the following line to use the current thread.
        super(Looper.getMainLooper());
        mInstance = new WeakReference<>(clazz);
    }

    @Override
    public void handleMessage(Message msg) {
        T clazz = mInstance.get();
        if (clazz != null) {
            clazz.handleMessage(msg);
        }
    }
}

的接口:

public interface MessageHandler {

    void handleMessage(Message msg);

}

我是这样使用的。但我不能百分百确定这是否安全。也许有人可以对此发表评论:

public class MyClass implements MessageHandler {

    private static final int DO_IT_MSG = 123;

    private MainThreadHandler<MyClass> mHandler = new MainThreadHandler<>(this);

    private void start() {
        // Do it in 5 seconds.
        mHandler.sendEmptyMessageDelayed(DO_IT_MSG, 5 * 1000);
    }

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {
            case DO_IT_MSG:
                doIt();
                break;
        }
    }

    ...

}

2017-03-27 13:40:04

如果您正在使用Kotlin，只需在声明嵌套类时删除inner关键字即可。

Kotlin中的嵌套类默认情况下是静态的，使用inner声明它们使它们成为非静态的。

将嵌套的Handler子类声明更改为

class myService : Service() {

inner class IncomingHandler : Handler(Looper.getMainLooper()) {
/////
}

}

class myService : Service() {

class IncomingHandler : Handler(Looper.getMainLooper()) {
/////
}

}

2022-08-09 07:33:00

这个Handler类应该是静态的，否则可能会发生泄漏

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