Bounds and anchoring of programmatic UIScrollView with zooming - iphone

Question

So, I've managed to create a UIScrollView with zooming method programmatically, but I'm kind of stuck how to solve an issue I'm having with zooming:
When I zoom in or out the point at where it expands/retracts does not happen where I do the pinch gesture, it happens on a corner.
After zooming in or out, it will leave extra space outside the bounds, and I cannot scroll the image more than half the width & height of the image.
Other than this, I'm so close to getting it working 100%. I've tried playing around with achorpoints, but it looks like the scroll view and image view does not respond to this.
Here is the important stuff in the code listing:
UIScrollView *mapScrollView;
UIImageView *mapImageView;
CGFloat lastScale = 0;
NSMutableArray *map_List;
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
mainMenuAppDelegate *del = (mainMenuAppDelegate *)[[UIApplication sharedApplication] delegate];
map_List = [[NSMutableArray alloc] init];
[map_List addObject:#"Pacific_Map_8bit.png"];
[map_List addObject:#"Atlantic_Map_8bit.png"];
CGRect mapScrollViewFrame = CGRectMake(0, 0, 1024, 768);
mapScrollView = [[UIScrollView alloc] initWithFrame:mapScrollViewFrame];
mapScrollView.contentSize = CGSizeMake(2437, 1536);
UIImage *mapImage = [UIImage imageNamed:[map_List objectAtIndex:mapNum]];
mapImageView = [[UIImageView alloc] initWithImage: mapImage];
mapScrollView.bounces = NO;
[mapImage release];
[mapScrollView addSubview:mapImageView];
[self addSubview:mapScrollView];
mapImageView.userInteractionEnabled = YES;
UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:#selector(scale:)];
[mapImageView addGestureRecognizer:pinchRecognizer];
[pinchRecognizer release];
}
return self;
}
// the scale method thats triggered to zoom when pinching
-(void)scale:(id)sender {
if([(UIPinchGestureRecognizer*)sender state] == UIGestureRecognizerStateEnded) {
lastScale = 1.0;
return;
}
CGFloat scale = 1.0 - (lastScale - [(UIPinchGestureRecognizer*)sender scale]);
NSLog(#"map scale %f", scale);
CGFloat mapWidth = mapImageView.frame.size.width;
CGFloat mapHeight = mapImageView.frame.size.height;
NSLog(#"map width %f", mapWidth);
if(scale>=1 & mapWidth<=4000 || scale<1 & mapWidth>=1234){
CGAffineTransform currentTransform = [(UIPinchGestureRecognizer*)sender view].transform;
CGAffineTransform newTransform = CGAffineTransformScale(currentTransform, scale, scale);
[[(UIPinchGestureRecognizer*)sender view] setTransform:newTransform];
lastScale = [(UIPinchGestureRecognizer*)sender scale];
}
mapScrollView.contentSize = CGSizeMake(mapWidth, mapHeight);
}
Thanks!

Answer 1

UIScrollView has built-in zooming support. All you need to do is set the minimumZoomScale and maximumZoomScale properties, and return a view to be used for zooming using viewForZoomingInScrollView.