Question

I created a live wallpaper service using AndEngine library. On screen there are a number of bird Sprite objects that flying repeatedly from the left to right started in random y-coordinate (I’m using LoopEntityModifier and PathModifier for this, see my previous question if you’re curious). The birds shouldn’t start flying in same time, but there is a gap/interval about 3 seconds before another bird showed up from left most screen.

The question is what technique that I have to use to achieve that?

I had created array of Sprites to hold the bird sprites. The code is like this…

public class MyLiveWallpaperService extends BaseLiveWallpaperService {

    private BirdSprite[] birdSprites;    // BirdSprite is actually an extension class from AnimatedSprite
    ...

    @Override
    public Scene onLoadScene() {
        ...
        birdSprites= new BirdSprite[4];
        for (int i=0; i<4; ++i) {
            birdSprites[i] = new BirdSprite(0, 0, birdTextureRegion);

            scene.getChild(LAYER_FRONT).attachChild(birdSprites[i]);
        }
    }
}

The above code produces four birds that show-up on left screen in same time. I tried by adding Thread.sleep(3000) before calling attachChild, but it affects whole application. The live wallpapaper application become hanged for several seconds when started.

Answer 1

This is the solution I found by using TimerHandler:

    scene.registerUpdateHandler(new TimerHandler(3, true, new ITimerCallback() {

        @Override
        public void onTimePassed(TimerHandler pTimerHandler) {
            // your code here will be executed every 3 seconds (see 1st argument of TimerHandler)
            ...
            scene.getChild(LAYER_FRONT).attachChild(birdSprites[i]);
        }
    }));

Please let me know if you have better solution.