Toast created in an IntentService never goes away

Question

I have an IntentService that downloads some files. The problem is that I create a Toast inside the IntentService like this

Toast.makeText(getApplicationContext(), "some message", Toast.LENGTH_SHORT).show();

The Toast will never disappear event if I exit the app. The only way to destroy it is to kill the process.

What am I doing wrong?

Tantivy

There's no reason not to create a Toast from a service. From the notification dev guide: >If you create a toast notification from a Service, it appears in front of the Activity currently in focus. – Homelike

That must be wrong, because it doesn't work when you test it with IntentService. @rony's solution works best. – Lowercase

Answer 1

You shouldn't create Toasts from a Service. You should use a Notification instead.

Pacification

Wrong. from developer.android.com/guide/topics/ui/notifiers/toasts.html "A toast can be created and displayed from an Activity or Service". Its not working because "Service" runs on Main thread, whereas "Intent service" run on another thread. – Hollingshead

Just because you can do a thing doesn't mean you should do a thing. You shouldn't create toasts from a service. – Pacification

@Qberticus, can you update your answer with a code example of how Notification would be used in this case? – Positivism

Why should we use Notifications instead of Toasts from services? Is it because of a technical limitation? Is it because the user mightn't be looking at the screen? – Barbarity

A notification would be a good solution. Only issue is that user may turn off notifications for an app. – Mclaren

Answer 2

The problem is that IntentService is not running on the main application thread. you need to obtain a Handler for the main thread (in onCreate()) and post the Toast to it as a Runnable.

the following code should do the trick:

@Override
public void onCreate() {
    super.onCreate();
    mHandler = new Handler();
}

@Override
protected void onHandleIntent(Intent intent) {
    mHandler.post(new Runnable() {            
        @Override
        public void run() {
            Toast.makeText(MyIntentService.this, "Hello Toast!", Toast.LENGTH_LONG).show();                
        }
    });
}

Balaklava

@rkmax android studio for some reason defaults to import java.util.logging.Handler; (which is abstract) change it to import android.os.Handler; – Yard

@rony If I call this from JNI I get a null pointer exception, any idea why that is? Do I need a new thread in JNI? – Hoplite

Is new Handler() call expensive? – Ursala

Answer 3

This works for me:

public void ShowToastInIntentService(final String sText) {
    final Context MyContext = this;

    new Handler(Looper.getMainLooper()).post(new Runnable() {
        @Override
        public void run() {
            Toast toast1 = Toast.makeText(MyContext, sText, Toast.LENGTH_LONG);
            toast1.show();
        }
    });
};

Noneffective

Perfect solution – Clinch

Answer 4

IntentService will create a thread to handle the new intent, and terminated it immediately once the task has done. So, the Toast will be out of controlled by a dead thread.

You should see some exceptions in the console when the toast showing on the screen.

Josefinejoseito

+1 for pointing out worker thread mechanism in IntentService. – Welford

Answer 5

For people developing in Xamarin studio, this is how its done there:

Handler handler = new Handler ();
handler.Post (() => {
    Toast.MakeText (_Context, "Your text here.", ToastLength.Short).Show ();
});

Crabber

Answer 6

To show a toast when the user is in one of the application activity.

Just need a reference of the current activity, and call it with this sample code:

public void showToast(final String msg) {
    final Activity a = currentActivity;
    if (a != null ) {
        a.runOnUiThread(new Runnable() {

            @Override
            public void run() {
                Toast.makeText(a, msg, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

There is a lot of options to get the current activity, check this question: How to get current foreground activity context in android?

But I use this approach:

The application must have:

private Activity currentActivity = null;

public Activity getCurrentActivity() {
    return currentActivity;
}

public void setCurrentActivity(Activity mCurrentActivity) {
    this.currentActivity = mCurrentActivity;
}

Each activity must have:

@Override
protected void onResume() {
    super.onResume();
    ((MyApplication) getApplication()).setCurrentActivity(this);

}
@Override
protected void onPause() {
    super.onPause();
    ((MyApplication) getApplication()).setCurrentActivity(null);
}

Scales

Call super.onPause() from onPause – Educative

Oh my god a bug!... But it's gone now. – Arand