In Android, how do I smoothly fade the background from one color to another? (How to use threads)

Question

I\'ve been playing with Android programming on and off for a couple of weeks, and I\'m trying to get something to work that seems simple, but I think I am missing something.

Answer 1

In your loop, your setting on background is so fast that the UI is not (will not) able to schedule the update of display. Yes, you better use a second thread to update the background or else you will stall the UI thread. Try following:

LinearLayout screen;
Handler handler = new Handler();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    screen = (LinearLayout) findViewById(R.id.screen);

    (new Thread(){
        @Override
        public void run(){
            for(int i=0; i<255; i++){
                handler.post(new Runnable(){
                    public void run(){
                        screen.setBackgroundColor(Color.argb(255, i, i, i));
                    }
                });
                // next will pause the thread for some time
                try{ sleep(10); }
                catch{ break; }
            }
        }
    }).start();
}

This is a threaded version of your code.