CODEWITHSUNDEEP
androidmultithreadingserviceandroid-activity
uzay95
uzay95

Reputation: 16622

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

I've 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);
}

Upvotes: 0

Views: 2370

Answers (5)

JaskeyLam
JaskeyLam

Reputation: 15755

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).

Upvotes: 0

CommonsWare
CommonsWare

Reputation: 1006624

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.

Upvotes: 1

Will Kru
Will Kru

Reputation: 5212

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

Upvotes: 0

Haphazard
Haphazard

Reputation: 10948

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.

Upvotes: 1

Konstantin Milyutin
Konstantin Milyutin

Reputation: 12366

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.

Upvotes: 0

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