Question

Hello guys I hope you can help me. I try to code a game but I fail at collision. I searched a lot and found out that the bounding box method (to create a unvisible rectangle around the sprite) is the best soulution for me. But the intersect method is not working for me. I have two bitmap sprites which collide, but in the LogCat there is no collision…

Sprite No. 1 Class

public Sprite(GameView theGameView, Bitmap bmp) {
    this.theGameView = theGameView;
    this.bmp = bmp;
    this.width = bmp.getWidth();
    this.height = bmp.getHeight();
    ySpeed = 0;
    xSpeed = 1;
}


 public Rect bounds() {         
        return (new Rect(x,y,width,height));
    }


public void onDraw(Canvas canvas) {
    canvas.drawBitmap(bmp, x, y, null);
}

Sprite No. 2 Class

public FourthSprite(GameView theGameView, Bitmap bmp) {
    this.theGameView = theGameView;
    this.bmp = bmp;
    this.width = bmp.getWidth();
    this.height = bmp.getHeight();
    ySpeed =  0;
    xSpeed = -1;
}


public Rect bounds() {
    // TODO Auto-generated method stub
    return (new Rect(x,y,width,height));
}

public void onDraw(Canvas canvas) {
         canvas.drawBitmap(bmp, x, y, null);
}

}

GameView Class

public void collision() {

   Rect r1 = theSprite.bounds();  // Sprite on left side
       Rect r4 = theSprite4.bounds(); // Sprite on right side

  if (r1.intersect(r4)){

       collision = true;
       Log.v("Log Tag", "COLLISION :D :D :D :D :D :D :D");
   }

  else       {
       collision = false;
       Log.v("Log Tag", "NO COLLISION");
  }
    }

If it helps i can also upload a video.

Edit: http://youtu.be/wYxZ7nKsmdw
I figured out, that collision is working, when one sprite does not move arround and the x,y coordinates are 0. What could be the problem?

Answer 1

According to the video and the data you’re outputting into LogCat, something seems to be wrong with the move function (which hasn’t been listed in your question).

The left coordinates of the rectangles are changing, however the right coordinates aren’t. After some time the left coordinate of one rectangle becomes greater than right coordinate, which results in the intersects function to return false.

On a side note, you should think about structuring your code differently, try to use inheritance instead of a lot of very similar classes.