android - 如何在多个 Activity 中使用服务？

Question

我在编写服务时遇到问题，该服务应该适用于多个 Activity 。我编写了一个简单的服务和一个进行绑定(bind)并可以返回服务对象的中介类。这是简单的服务类:

public class ServerConnectionService extends Service{

private static final String TAG = "ServerConnectionService";
private final Binder binder=new LocalBinder();

@Override
public void onCreate() {
    super.onCreate();
}

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

@Override
public IBinder onBind(Intent intent) {
    return binder;
}

public class LocalBinder extends Binder {
    ServerConnectionService getService() {
        return ServerConnectionService.this;
    }
}
}

这是中介类:

public class ServiceConnectionBinder{

private ServerConnectionService m_SrvConnection=null;
private ServiceConnection m_OnService;
private boolean m_IsBound;
private Activity m_Client;

public ServiceConnectionBinder(Activity  i_Activity)
{
    m_IsBound = false;
    this.m_Client = i_Activity;
    this.m_OnService=new ServiceConnection() {
        public void onServiceConnected(ComponentName className,IBinder rawBinder) {
                m_SrvConnection=((ServerConnectionService.LocalBinder)rawBinder).getService();
            }

            public void onServiceDisconnected(ComponentName className) {
                m_SrvConnection=null;
            }
        };

    doBindService();
    Log.d("ServiceConnectionBinder", "finished Ctor");
}

private void doBindService() {
    if(!m_IsBound)
    {
        m_Client.bindService(new Intent(m_Client, ServerConnectionService.class), m_OnService, Context.BIND_AUTO_CREATE);
        m_IsBound = true;
    }

    if(m_SrvConnection == null)
    {
        Log.d("ServiceConnectionBinder",".doBindService cannot bind " + ServerConnectionService.class.toString() + " to " + this.toString());
    }
}

public void doUnbindService() {
    if (m_IsBound) {
        // Detach our existing connection.
        m_Client.unbindService(m_OnService);
        m_IsBound = false;
    }
}

public ServerConnectionService getServerConnectionService()
{
    if(m_IsBound)
    {
        Log.d("ServiceConnectionBinder", "getServerConnectionService m_IsBound = " + m_IsBound); 
    }
    return m_SrvConnection;
}
}

客户端 Activity 有以下数据成员:

private ServiceConnectionBinder m_SrvcConnectionBinder=null;
private ServerConnectionService m_SrvConnection=null;

并在 onCreate() 中执行以下代码:

m_SrvcConnectionBinder = new ServiceConnectionBinder(this);
m_SrvConnection = m_SrvcConnectionBinder.getServerConnectionService();

问题是在 onCreate() 之后，m_SrvConnection 始终为 null。

如果您有任何其他实现方法，我们非常欢迎您分享..

Answer 1

problem is that after the onCreate(), the m_SrvConnection is always null.

当然。绑定(bind)请求甚至不会开始，直到主应用程序线程再次获得控制权(即，您将控制权返回给操作系统)。

在调用 onServiceConnected() 之前，您不能使用 m_SrvConnection。