Question

Possible Duplicate:
Android Service makes Activity not responding

I use service to synchronize data between database and view. But the service does not work properly, whenever I use service to work long task, the view stop response (I can’t do any event in UI) and I have to wait the service has done. Here is my service:

public class SyncService extends Service{
private static final String TAG = "SyncService";
@Override
public void onCreate()
{       
    super.onCreate();
}

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

@Override
public IBinder onBind(Intent intent)
{
    Log.d(TAG, "call onBind");
    return new DataManagerBinder();
}

private class DataManagerBinder extends Binder implements IUserDataManager
{
    @Override
    public void doProcess(Activity mView)
    {
        //do some long task (not touch UI thread)
        // this will cause the view not response
        syncDB();
        // update view after process completed
        mView.updateViewOnComplete();
    }

}

I try to bind this service in client activity

//the interface to handle binder 
IUserDataManager  viewManager = null;    
ServiceConnection serviceConnection = new ServiceConnection()
{

    @Override
    public void onServiceDisconnected(ComponentName name)
    {
        Log.i(TAG, "connection closed unexpectedly");
        viewManager = null;
    }

    @Override
    public void onServiceConnected(ComponentName name, IBinder binder)
    {
        Log.d(TAG, "serviceConnection onServiceConnected");
        viewManager = (IUserDataManager) binder;
        viewManager.doProcess(MyActivity.this);
    }
};

    Intent intent = new Intent(MyActivity.this, SyncService.class);
    bindService(intent, serviceConnection, Context.BIND_AUTO_CREATE);

Please give me the solution for that. Thanks in advance!

Answer 1

While others have given some responses, I don’t know if the main point has been emphasized:
While a Service sounds like something that would automatically run in the background, it does not. It’s merely a piece of code that can react to intents without maintaining a UI. However, the UI thread still does the processing for the Service.

By contrast, it looks like what you want, is a Service that sits in the background and does some work in a background thread. You will use the Service class to spawn a new thread, this is typically done on response to some intent, which you can define (usually in your onStart() or something similar). You will probably start a new thread which actually does the work updating the database, etc…, and use your main Service to coordinate to that thread.

As it looks like you also want to communicate with the service, you will have to implement an appropriate Messenger and Handler pair to keep track of messages you pass between the UI and the Service (coordinating a background thread), and also (possibly) some way (also perhaps a messenger) of coordinating between the Service and the background thread.

As others have noted, you can also use AsyncTask to do things on the UI thread and use a background thread “seamlessly.”