Question

Developing a game with AndEngine GLES2

I am having an issue trying to change the scale of a rectangle that I have added to a scene from within a TimerHandlers callback. Whenever the timer ticks it makes a percentage calculation and then within the OnTimePassed ITimerCallback it tries to set the scale of the rectangle in the scene. Unless I declare the rectangle as static I keep getting a nullreferenceexception error.

I know that this is a scope issue, my question is, should I be declaring the objects I need to access from within the timercallback as static or is there an “accepted way” to get access to Activity level objects from within a timercallback?

PlayerRecastTimer = new TimerHandler(0.5f, true, new ITimerCallback(){
    private float recastTime = playerSpellToCast.getRecastTime();

    public void onTimePassed(TimerHandler pTimerHandler) {
        if(recastTime == 0) {
            mAct.GetEngine().unregisterUpdateHandler(pTimerHandler);
            mAct.GetQueue().RemovePlayerSpell();
            pRecast.setScaleX(1);
            RunScene();
        }

        float recastScale;

        recastScale = recastTime / playerSpellToCast.getRecastTime();
        pRecast.setScaleX(recastScale); //blows up here when attempting to scale the rectangle
        recastTime -= 0.5;
    }
});

Answer 1

If your PlayerRecastTimer is a member of a class that contains pRecast, then you can reference it using ClassName.this.

Example: If you have a class named LoadingScreenActivity and it has a rectangle called pRecast, then you can access pRecast in your onTimePassed() function by using

LoadingScreenActivity.this.pRecast.setScaleX(1);