ios - Keep moving images bouncing within frame width and height -

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i trying figure out how keep image within frame width , height. right wraps around. preferably create stays within frame , bounces around inside.

-(void) movebutterfly {     bfly.center = cgpointmake(bfly.center.x + bfly_vx, bfly.center.y + bfly_vy);      if(bfly.center.x > framewidth)     {         bfly.center = cgpointmake(0, bfly.center.y + bfly_vy);     }     else if (bfly.center.x < 0)     {         bfly.center = cgpointmake(framewidth, bfly.center.y + bfly_vy);     }      if(bfly.center.y > frameheight)     {         bfly.center = cgpointmake(bfly.center.x + bfly_vx, 0);     }     else if (bfly.center.y < 0)     {         bfly.center = cgpointmake(bfly.center.x + bfly_vx, frameheight);     } } 

-(void)movebutterfly{     static int dx = 1;     static int dy = 1;     if (bfly.frame.origin.x >= self.view.bounds.size.width - bfly.bounds.size.width) {         dx = -dx;     }     if (bfly.frame.origin.y >= self.view.bounds.size.height - bfly.bounds.size.height) {         dy = -dy;     }     if (bfly.frame.origin.x <= 0) {         dx = -dx;     }     if (bfly.frame.origin.y <= 0) {         dy = -dy;     }     cgpoint point = bfly.center;     point.x += dx;     point.y += dy;     bfly.center = point; }

keep calling function using nstimer @ rate want update position. here dx , dy velocity @ butterfly move.


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