Animate sprites using drawableAnmiation

Issue

I have a design question so I don't start off on the wrong way. I am planning to have a sprite where it animates moving and I want to move this sprite around (changing position once every second).

I noticed that some tutorial talk about having a game loop,, onDraw on Canvas, bitmap ..etc

However, I am thinking of using drawableAnimation where I specify the set of images to load in xml and call start on it. Then I can just draw at the position required every second ( no loop, it is more like listener that gets called every sec from different process).

Do you forsee an issue? Any problem with above method

Thank you

Solution

Drawable Animation requires a fixed frame animation. Think of it like a flip book. The drawable would have to be the entire size of your canvas and your sprite would have to be prerendered on top of some transparent background to achieve your affect. It also would require a large amount of texture memory depending on the size and number of frames.

The "game loop" as you stated is sort of what Android already provides in a way. Inside of the standard canvas setup you have your "main Thread". So with an entity like a Handler you could tick frames if you like.

i.e.

Handler handler;
public void onCreate(Bundle bundle) {
super.onCreate(bundle);
handler = new Handler();
handler.post(new Runnable() {
   public void run() {
       boolean isLastFrame = drawFrame();
       if (!isLastFrame) {
           handler.postDelayed(this, ONE_SECOND_MILLIS);
       }
   }
});

This is not the greatest really either.

You could also encapsulate your sprite inside a View or own custom Drawable and inside your onDraw() method, you would update your canvas.

public void onDraw(Canvas canvas) {
  // clear canvas
  mPaint.setColor(Color.WHITE);
  canvas.drawPaint(mPaint);
  // Draw current
  mPaint.setColor(Color.BLACK);
  canvas.drawRect(rect, mPaint);
}

public void moveSprite() {
  rect.offset(3, 3);
  invalidate();
}

You could also, if using a View, use an ObjectAnimator to translate the View from position (x1, y1) to (x2, y2).

public void moveTo() {
  if (!moveNeeded) {
    return;
  } 
  View view  = getMyView();
  view.animate().x(1).y(1).setListener(new Animator.AnimatorListener() {
    public void onAnimationCancel(Animator a) { }
    public void onAnimationStart(Animator a) {
    }
    public void onAnimationEnd(Animator a) {
      moveTo();
    }
    public void onAnimationRepeat(Animator a) {
    }
  });
}

Answered By - Greg Giacovelli