Question

我有一个关于套接字对象的问题，我通过Service实例传递到我的Android活动中。

套接字对象总是返回null，我不明白为什么。我在其他活动中使用相同的方法，它工作正常。有人可以看看吗？

这是我的代码：

**Service class code:**

public class SocketService extends Service {
    // Create subclass of IBinder and bind it to local class instance
private final IBinder mBinder = new LocalBinder();      
public class LocalBinder extends Binder { 
    SocketService getService() { 
        return SocketService.this; 
        }
    }

@Override
public IBinder onBind(Intent arg0) {
    return mBinder;
}

@Override
public void onCreate() {
        try {
            socket = new SocketIO(URL);
            socket.connect(new IOCallback() {

                // Tell if connection was established
                @Override
                public void onConnect(){    
                }

                // Server Message
                @Override
                public void on(String event, final IOAcknowledge ack,
                        Object... arg) {
            }

                @Override
                public void onDisconnect() {
                    socket.reconnect();
                }

                @Override
                public void onError(SocketIOException arg0) {
                    Log.e("ERROR", "No Connection to host");
                    error = true;
            }    

                @Override
                public void onMessage(String arg0, IOAcknowledge arg1) {        
                }

                @Override
                public void onMessage(JSONObject arg0, IOAcknowledge arg1) {    
                }   
            });

        } catch (MalformedURLException e) {
            Log.e("error", "Wrong Server URL" + e); }
        } else {
            Log.e("ERROR", "No connection possible");
            }
}

@Override
public void onDestroy() {
    super.onDestroy();
    socket.disconnect();
    stopSelf();
}

public SocketIO getSocket(){
    return socket;
}

这里是null套接字对象的活动：

Activity code:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_menu);

 socketConnection = new ServiceConnection() {
        public void onServiceConnected(ComponentName className,
                IBinder service) {
            LocalBinder binder = (LocalBinder) service;
            socketService = binder.getService();
            isBound = true;
        }

        public void onServiceDisconnected(ComponentName arg0) {
            socketService = null;
        }
       };

        // Bind to socket service
        Intent serviceIntent = new Intent(ContactMenuActivity.this, SocketService.class);
        bindService(serviceIntent, socketConnection, Context.BIND_AUTO_CREATE);


        socket = socketService.getSocket(); // This code always returns null 
but only for this activity, it works with other activities with same approach

Answer 1

好的，我找到了问题的答案。在任何一种情况下，显然绑定到服务可能需要一些时间，比我的活动启动时间长。

解决方案是在意图连接到服务后立即检查IBinder对象的返回值：

Service Class

@Override
public IBinder onBind(Intent arg0) {
    Log.d("DEBUG", "Connected to service");
    return mBinder;
}

Activity Class

if (mBinder != null)
socket = socketService.getSocket();

Socket对象在Activity绑定到Service中返回null

1 个答案: