onHandleIntent - Wallpaper change not working correctly when app is closed

Question

I am using the IntentService to change wallpaper in the background. It gets invoked on receiving of a push notification. Below code works fine if notification is received while the application is open. But does not work if the Application is closed/killed (by swiping it away with help of menu button)

@Override
protected void onHandleIntent(Intent intent) {

    //Toast.makeText(this, "Intent", Toast.LENGTH_SHORT).show();
    sharedpreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);

    String imageUrl = intent.getExtras().getString("imageUrl");

    try {
        URL url;
        try {
            WallpaperManager myWallpaperManager = WallpaperManager
                    .getInstance(MySingletonClass.mainActivityInstance);


            url = new URL(
                    imageUrl);
            Bitmap bmp = BitmapFactory.decodeStream(url
                    .openConnection().getInputStream());
            myWallpaperManager.setBitmap(bmp);


        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

    PushReceiver.completeWakefulIntent(intent);
}

Works fine when the application is opened. When closed/killed, it isn't able to create instance of WallpaperManager and throws below exception.

W/System.err: java.lang.NullPointerException
W/System.err: at android.app.WallpaperManager.getInstance(WallpaperManager.java:361)

Answer 1

Instead of using MySingletonClass.mainActivityInstance which was actually null as pointed by @qbix, Use context of the IntentService which is this.

try {
        WallpaperManager myWallpaperManager = WallpaperManager
                .getInstance(this);


        url = new URL(
                imageUrl);
        Bitmap bmp = BitmapFactory.decodeStream(url
                .openConnection().getInputStream());
        myWallpaperManager.setBitmap(bmp);


    }