Question

I’m trying to have an image wrap around the window (When it falls off the left, it reappears on the right) I have a timer calling a function containing this:

bgImage.center = CGPointMake(bgImage.center.x - 5, bgImage.center.y);
if (bgImage.center.x < -self.view.frame.size.width/2)
    bgImage.center = CGPointMake(bgImage.center.x + self.view.frame.size.width, bgImage.center.y);
    NSLog(@"%f",bgImage.center.x);

When it falls off the screen, it comes back half way, then a little less each time. The console returns very large values for an x value

2012-02-09 13:33:44.229 Parkour Runner[1351:f803] 2: 28990.000000
2012-02-09 13:33:44.328 Parkour Runner[1351:f803] 2: 29285.000000
2012-02-09 13:33:44.429 Parkour Runner[1351:f803] 2: 29580.000000
2012-02-09 13:33:44.528 Parkour Runner[1351:f803] 2: 29875.000000

Answer 1

How about this instead? It will take into consideration the size of the image.

bgImage.frame = CGRectMake(bgImage.origin.x - 5.0f, bgImage.origin.y, bgImage.size.width, bgImage.size.height);

if ( (bgImage.frame.origin.x + bgImage.frame.size.width) < 0.0f) {
    bgImage.frame = CGRectMake(self.view.frame.size.width, bgImage.origin.y, bgImage.size.width, bgImage.size.height);
}