Question

I would like to create a “Flash” class to display a white flash screen (200ms) as easily as a toast, like this:

Flash.create(context).show();

• This layer should appear instantly then gradually disappear (alpha transition)
• It must not catch events
• It must adapt to the screen rotation
• It can be created from any activity

I looked for a solution via WindowManager but I am having some difficulties.
What solution do you recommend?

Answer 1

After searching for many hours, it seems impossible to delegate events from one window to another. So the final functional solution I’ve found is to extend an activity so that it achieves this flash effect. For those who are interested in it, here’s my subclass:

public class FlmActivity extends Activity {


    private final static int DURATION_FADEIN = 50;
    private final static int DURATION_FADEOUT = 200;
    private final static int DURATION_INTERVAL = 200;
    private View view;
    private AnimationSet anim;
    private int count;


    public FlmActivity() {
        super();
    }


    @Override protected void onPostCreate(Bundle state) {
        super.onPostCreate(state);
        view = new View(this) {{
            setBackgroundColor(0xffffffff);
            setVisibility(View.INVISIBLE);
        }};
        anim = new AnimationSet(false) {{
            addAnimation(new AlphaAnimation(0, 1) {{
                setDuration(DURATION_FADEIN);
            }});
            addAnimation(new AlphaAnimation(1, 0) {{
                setStartOffset(DURATION_FADEIN);
                setDuration(DURATION_FADEOUT);
            }});
            addAnimation(new Animation() {{
                setStartOffset(DURATION_FADEIN + DURATION_FADEOUT);
                setDuration(DURATION_INTERVAL);
                setAnimationListener(new AnimationListener() {
                    @Override public void onAnimationStart(Animation anim) {}
                    @Override public void onAnimationRepeat(Animation anim) {}
                    @Override public void onAnimationEnd(Animation anim) {
                        flash(count - 1);
                    }
                });
            }});
        }};
        addContentView(view, getWindow().getAttributes());
    }


    @Override protected void onDestroy() {
        ((ViewGroup) view.getParent()).removeView(view);
        super.onDestroy();
    }


    public final void flash(int count) {
        if((this.count = count) > 0) {
            view.startAnimation(anim);
        }
    }


}

Code to call flash effect in an extended activity:

flash(10);

With this implementation, the events pass through the layer