Question

I’m trying to make a rectangle move across the iPhone screen by changing its x value then redrawing. I’m new to Objective C, can someone point me to a tutorial on how to do this? It doesn’t look like DrawRect accepts parameters, should I make a public variable to store the rectangle x value?

It looks like I need to run a for loop to scale through x values for the rectangle incrementally, and after each x is changed call setNeedsDisplay. I have quite a few files and default functions I don’t recognize already. Where would it be appropriate to place the for loop?

Answer 1

You can use the UIView transformation methods. Just go to the documentation and search for UIView and there should be an animations section. It is quite easy actually. I would post code here, but that should be self explanatory.

---

Something like this:

-(void)animateLeft
{
    [UIView beginAnimations:ANIMATE_TO_LEFT context:nil];
    [UIView setAnimationDelay:0];
    [UIView setAnimationDuration:0.2f];
    [UIView setAnimationCurve:UIViewAnimationCurveLinear];
    [UIView setAnimationBeginsFromCurrentState:YES];
    [UIView setAnimationDelegate:self];

    CGRect updateFrame = [self frame];
    updateFrame.origin.x = updateFrame.origin.x-distanceToMove;
    [self setFrame:updateFrame];

    [UIView commitAnimations];
}