android - 从 AsyncTask 到 Activity 的消息

Question

我正在尝试从服务中嵌入的异步任务向我的主要 Activity 发送消息。基本上，异步任务必须在输入时阻塞，它不能在主 Activity 线程中运行(阻塞已从下面的示例代码中删除)。但是当数据进来时，我需要将它发送到主要 Activity 。我发现下面发送的消息永远不会成功。如果答案是在异步任务中移动绑定(bind)，您该怎么做？如果可能的话，指向示例代码会有很大帮助。

public class InputService2 extends Service {
int bufferSize = 1024;
Process process;
DataInputStream os;
TextView inputView;
byte[] buffer = new byte[bufferSize];
private MyAsyncTask inputTask = null;
       public void onCreate(){
           inputTask = new  MyAsyncTask();
           inputTask.execute((Void[])null);

       }
       private class MyAsyncTask extends AsyncTask<Void,Void,Void> {

        int mValue = 0;
        static final int MSG_SET_VALUE = 3;
            protected void onProgressUpdate(Void progress){

            }

            protected void onPostExecute(Void result) {

            }

            protected Void doInBackground(Void... params) {

                int i = 0;


                try {
                    mValue = 0x23;
            Message message =     Message.obtain(null,MSG_SET_VALUE,mValue,0);
                    mMessenger.send(message);
                }
                catch (Exception e) {

                }


            }
        } 
       class IncomingHandler extends Handler {
            @Override
            public void handleMessage(Message msg) {
            }
        }
        final Messenger mMessenger = new Messenger(new IncomingHandler());
        public IBinder onBind(Intent intent) {
            return mMessenger.getBinder();
        } 

}

下面是 Activity 内部:

class IncomingHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        Context context = getApplicationContext();
        int duration = Toast.LENGTH_LONG;
        Toast toast = Toast.makeText(context, msg.arg1, duration);
        toast.show();
    }
}

boolean mBound;
private ServiceConnection mConnection = new ServiceConnection() {
    public void onServiceConnected(ComponentName className, IBinder service) {
        // This is called when the connection with the service has been
        // established, giving us the object we can use to
        // interact with the service. We are communicating with the
        // service using a Messenger, so here we get a client-side
        // representation of that from the raw IBinder object.
        mService = new Messenger(service);
        mBound = true;
    }

    public void onServiceDisconnected(ComponentName className) {
        // This is called when the connection with the service has been
        // unexpectedly disconnected -- that is, its process crashed.
        mService = null;
        mBound = false;
    }
};

protected void onStart() {
    super.onStart();
    // Bind to the service
    bindService(new Intent(this, InputService2.class), mConnection,
            Context.BIND_AUTO_CREATE);
}

Answer 1

看起来您的示例基于 http://developer.android.com/reference/android/app/Service.html#RemoteMessengerServiceSample 处的 javadoc 引用，但是您遗漏了很多实际使它起作用的实现细节。您必须返回并实现该示例中引用的全部功能才能使用该特定模式:请仔细注意 IncomingHandler 类中的 REGISTER_CLIENT 和 UN_REGISTER_CLIENT 实现部分，因为这些是实际确保 Message 可以从为 Activity 服务。