Move an UIImageView around in a UIScrollView - iphone

Question

I'm creating an application where I want to let the user move (not pan) an UIImageView around by dragging it on the screen. Additionally, I want the user to be able to zoom the UIImageView in and out.
As such I've been using a custom UIScrollView that forwards single touches to the 'contentView':
#implementation JM_UIScrollView
- (BOOL)touchesShouldBegin:(NSSet *)touches withEvent:(UIEvent *)event inContentView:(UIView *)view
{
NSSet *allTouches = [event allTouches];
NSLog(#"Checking for touches: %d", [allTouches count]);
if ([allTouches count] == 1) {
return YES;
}
return NO;
}
#end
Along with a custom UIImageView that implements touchesBegan and touchesMoved to determine where to move the UIImageView:
#implementation JM_UIImageView
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSSet *allTouches = [event allTouches];
if ([allTouches count] == 0)
return;
UITouch *firstTouch = [[allTouches allObjects] objectAtIndex: 0];
CGPoint touchLoc = [firstTouch locationInView: [self superview]];
touchOffset= CGPointMake(touchLoc.x-self.center.x,touchLoc.y-self.center.y);
NSLog(#"Currently at: %3.3f x %3.3f", touchLoc.x, touchLoc.y);
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
NSSet *allTouches = [event allTouches];
if ([allTouches count] == 0)
return;
UITouch *firstTouch = [[allTouches allObjects] objectAtIndex: 0];
CGPoint touchLoc = [firstTouch locationInView: [self superview]];
if ([allTouches count] == 1)
{
if ([firstTouch view] == self)
{
touchLoc.x -= touchOffset.x;
touchLoc.y -= touchOffset.y;
NSLog(#"Moved to: %3.3f x %3.3f", touchLoc.x, touchLoc.y);
self.center = touchLoc;
}
}
}
#end
This is then all glued together:
scrollView = [[JM_UIScrollView alloc] initWithFrame: [[UIScreen mainScreen] bounds]];
scrollView.delegate = self;
scrollView.bouncesZoom = YES;
scrollView.scrollEnabled = NO;
scrollView.backgroundColor = [UIColor redColor];
scrollView.clipsToBounds = YES;
UIImage *image = [UIImage imageNamed:#"berg.jpg"];
imageView = [[JM_UIImageView alloc] initWithFrame: CGRectMake(0, 0, 140, 230)];
imageView.image = image;
imageView.center = CGPointMake(200,300);
[imageView setUserInteractionEnabled: YES];
[scrollView addSubview: imageView];
scrollView.contentSize = CGSizeMake(140,230);
scrollView.minimumZoomScale = 0.2;
scrollView.maximumZoomScale = 1.1;
[window addSubview: scrollView];
// Override point for customization after application launch
[window makeKeyAndVisible];
The problem:
When I start the application, I can move the UIImageView just fine and fluently. I can zoom-in and still be able to move it around.
However, it seems that whenever I zoom back out to the maximum level I seem then unable to move the UIImageView around anymore. It will jump at times, but by a maximum of 10 pixels. Use of NSLog() shows the touchesBegan/touchesMoved methods on the JM_UIImageView are no longer called.
Does anyone have any idea on what I might be missing here?
EDIT:
Would also accept an answer for wether or not this is the only way of implementing pinch-zooming with the zoombounce animation.