Zoom UIScrollView with multiple images - iphone

Question

I have a UIScrollFrame that contains multiple UIImageViews.
What is the correct way of supporting zoom in such a control?
Which view should 'viewForZoomingInScrollView' return?

Answer 1

I finally implemented it by putting a scrollview within a scrollview.
This way, the inner view handles page swipes while the outer handles zoom.

Answer 2

Apple has a really nice piece of Sample Code that is all about UIScrollView and zooming and tiling. Check it out at
http://developer.apple.com/iphone/library/samplecode/ScrollViewSuite/index.html
This code is discussed in the Scoll Views session of WWDC2009. The video of that session is unfortunately not freely available, but you can buy it as part of the iPhone WWDC2009 video package.

Answer 3

Just put a scrollview within another.
Like that:
-(void)zoomToSelectedImage:(NSIndexPath *)indexPath
{
int currentPage = indexPath.row;
//The External Scrollview. It move back and forward
UIScrollView *contentViewZoom = [[UIScrollView alloc] initWithFrame:self.frame];
[contentViewZoom setBackgroundColor:[UIColor colorWithWhite:0.0 alpha:0.8]];
[contentViewZoom setContentSize:CGSizeMake(contentViewZoom.frame.size.width * [arrayOfImages count], contentViewZoom.frame.size.height)];
[contentViewZoom setPagingEnabled:YES];
[contentViewZoom setDelegate:self];
for (int i = 0; i < [arrayOfImages count]; i++) {
CGRect frame;
frame.origin.x = contentViewZoom.frame.size.width * i;
frame.origin.y = 0;
frame.size = contentViewZoom.frame.size;
//The Internal Scrollview. It allow you zoom the picture
UIScrollView *imageScrollView = [[UIScrollView alloc]initWithFrame:frame];
[imageScrollView setTag:1];
[imageScrollView setMinimumZoomScale:1.0];
[imageScrollView setMaximumZoomScale:3.0];
[imageScrollView setAlpha:1];
[imageScrollView setDelegate:self];
[imageScrollView setBouncesZoom:YES];
[imageScrollView setClipsToBounds:YES];
[imageScrollView setShowsHorizontalScrollIndicator:NO];
[imageScrollView setShowsVerticalScrollIndicator:NO];
[imageScrollView setContentSize:CGSizeMake(768, 1024)];
UIImage *image = [arrayOfImages objectAtIndex:i];
UIImageView* imgView = [[UIImageView alloc] init];
[imgView setImage:image];
[imgView setFrame:CGRectMake(0, 0, 768, 1024)];
imgView.bounds = self.bounds;
[imgView setClipsToBounds:YES];
[imgView setContentMode:UIViewContentModeScaleAspectFit];
[imgView setAutoresizingMask:UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight];
[imageScrollView addSubview:imgView];
[contentViewZoom addSubview:imageScrollView];
}
[self addSubview:contentViewZoom];
[contentViewZoom setAlpha:0.2];
//Positioning according to current position
CGRect frame;
frame.origin.x = contentViewZoom.frame.size.width * currentPage;
frame.origin.y = 0;
frame.size = contentViewZoom.frame.size;
[contentViewZoom scrollRectToVisible:frame animated:NO];
}
OBS.: In my case, the screen size is fixed (768x1024), you should change as you need.