how can I get return value from android services

Question

I got the problem that I don't know how can I fetch return value from services. Why I want return value from services is I want to show this return value in Activity page. Following is my services file and return value is retvalue.

public class SyncService extends Service{
    private String forSync, lastrecordfromlocal, userdefined;
    DatabaseUtil dbUtil = new DatabaseUtil(this);

    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @SuppressWarnings("deprecation")
    @Override
    public void onStart(Intent intent, int startId) {
        // TODO Auto-generated method stub
        super.onStart(intent, startId);   

        forSync = common.getInfoForSync(this); 
        String[] getlist = forSync.split(":");
        lastrecordfromlocal = getlist[0].toString(); 
        userdefined = getlist[1].toString();

        if (common.isNetAvailable(this) == true) {
            SyncServiceTask InstallData = new SyncServiceTask(this);
            try {
                String (((retvalue))) = InstallData.execute(lastrecordfromlocal, userdefined).get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }                               
        }        
        this.stopSelf();
    }

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

Answer 1

As far as I know, the common way for service to communicate with activity is by BROADCAST.

You can send a broadcast at the position you want to "return retvalue" by something like:

Intent retIntent = new Intent(ServiceReturnIntent);
retIntent.putExtra("retvalue", retvalue);
sendBroadcast(retIntent);

which ServiceReturnIntent and "retvalue" are all self-defined strings to identify the broadcast and value name.

And in your activity which wishes to catch the return value, you should have a broadcast receiver, with something like:

public class myActivity extends Activity implements BroadcastReceiver {
    TextView myTextView;

 @Override
     OnCreate(Bundle savedInstanceState) {
         setContentView(R.layout.simple_layout);
         myTextView = (TextView) findViewByID(R.id.simple_textview);
     }  

 @Override
    public void onReceive(Context context, Intent intent) {

        int action = jumpTable.get(intent.getAction());
        switch (action) {
    case ServiceReturnIntent:
            String valueFromService = intent.getStringExtra("retvalue");
                myTextView.setText(valueFromService);
                break;
            // handle other action 
         ......
    }
}

You can read this tutorial for more about broadcast in android.

EDIT modify sample code with setting it to a textview

Answer 2

You can bind service to the Activity:link

Your Service:

  public class SyncService extends Service {
  private final IBinder mBinder = new MyBinder();
  private String;

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {

     forSync = common.getInfoForSync(this); 
    String[] getlist = forSync.split(":");
    lastrecordfromlocal = getlist[0].toString(); 
    userdefined = getlist[1].toString();

    if (common.isNetAvailable(this) == true) {
        SyncServiceTask InstallData = new SyncServiceTask(this);
        try {
            String (((retvalue))) = InstallData.execute(lastrecordfromlocal, userdefined).get();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }                               
    }    
    return Service.START_NOT_STICKY;
  }

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

  public class MyBinder extends Binder {
    SyncService getService() {
      return SyncService .this;
    }
  }

  public String getRetValue() {
    return retvalue;
  }

}

And in Activity check the value:

SyncService mService;
    @Override
        protected void onStart() {
            super.onStart();
            // Bind to LocalService
            Intent intent = new Intent(this, SyncService .class);
            bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
        }

        @Override
        protected void onStop() {
            super.onStop();
            // Unbind from the service
            if (mBound) {
                unbindService(mConnection);
                mBound = false;
            }
        }

        /** Called when a button is clicked (the button in the layout file attaches to
          * this method with the android:onClick attribute) */
        public void onButtonClick(View v) {
            if (mBound) {

                Toast.makeText(this, "number: " + num, Toast.LENGTH_SHORT).show();
            }
        }

    /** Defines callbacks for service binding, passed to bindService() */
        private ServiceConnection mConnection = new ServiceConnection() {

            @Override
            public void onServiceConnected(ComponentName className,
                    IBinder service) {
                LocalBinder binder = (LocalBinder) service;
                mService = binder.getService();
                mBound = true;
            }

            @Override
            public void onServiceDisconnected(ComponentName arg0) {
                mBound = false;
            }
        };

Answer 3

if you want service to communicate with activity.we have two method.

1, you can use BROADCAST. you can send BROADCAST in service and use BroadcastReceiver in activity.

2, you also can use bindService to communicate activity.

public class LocalService extends Service {
    // This is the object that receives interactions from clients.  See
    // RemoteService for a more complete example.
    private final IBinder mBinder = new LocalBinder();

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

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

you can use iBinder to communicate with service