Accessing UI component on Activity from the Service class's Thread in Android

I'v开发者_StackOverflowe a class named by MyService which extends Service below. Everything will be ran until I remove the Toast.makeText... line in the run method of Thread.

Why? And how can I get access to the Activity components from the run method of Thread class?

public class MyService extends Service {

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

@Override
public void onCreate() {
    Toast.makeText(this, "This msg will be shown", Toast.LENGTH_LONG).show();
    Log.d("Bilgi", "This msg will be shown.");
    super.onCreate();
}

@Override
public void onStart(Intent intent, int startId) {
    Toast.makeText(this, "This msg will be shown", Toast.LENGTH_LONG).show();
    super.onStart(intent, startId);

    timer.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {
            try {
                Log.d("This msg will ","be shown"); //if I remove next line 
                Toast.makeText(this, "This msg will NOT be shown", Toast.LENGTH_LONG).show(); 

                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }, 5000, 8000);
}

And how can I get access to the Activity components from the run method of Thread class?

You don't. Use Messenger to send Message objects from the service to the activity's Handler. The activity -- and only the activity -- can update its widgets, and that only from the main application thread.

Here is a sample application demonstrating this.

Don't use Threads - use AyncTasks. Also, you shouldn't be accessing the Activity methods/UI through threads/tasks. Take a look at the first link to get an idea of how the Activity and its "threads" work together.

The only method I know is to use broadcast receiver inside your activity, which will catch you messages and update UI or whatever you want.

When creating the Toast, pass in the ApplicationContext which you can get through getApplicationContext()

The UI widgets are not thread-safe so you can not update the the UI widget unless in the Main(UI) Thread , in your case, making Toast is in another thread which is forbidden.

You may need to use something like Handler, and use Messenger to send message to the handler created in the activity UI thread. And then deal with the widgets in method handleMessage(Message msg).