iOS Multiple Images Paging and Zooming Issues

Question

There are a few threads out there related to this issues, but could not find a solid solution. Any help would be appreciated. This code works great if you give it one image. Zooms in perfect. You give it two images it scrolls threws the images fine but when you go to zoom in it always zooms into the first image? Not sure why the viewForZoomingInScrollView method doesn't figure out which view you are on. Code posted below

PagedScrollViewController.h

#import <UIKit/UIKit.h>
@interface PagedScrollViewController : UIViewController <UIScrollViewDelegate>
@property (nonatomic, strong) IBOutlet UIScrollView *scrollView;
@property (nonatomic, strong) IBOutlet UIPageControl *pageControl;
@property (nonatomic, strong) IBOutlet UIButton *cancelButtonClicked;
@property (nonatomic, strong) IBOutlet UILabel *headerTitle;
@property (nonatomic, strong) IBOutlet NSString *headerTitleS;
@property (nonatomic, strong) IBOutlet NSMutableArray *pageImages;
@property (nonatomic, strong) IBOutlet UITextView *caption;
@property (weak, nonatomic) IBOutlet UINavigationBar *navigationBar;
@property (nonatomic, strong) NSMutableArray *captionArray;

-(IBAction)cancelButtonClicked:(id)sender;

@end

PagedScrollViewController.m

@interface PagedScrollViewController ()
@property (nonatomic, strong) NSMutableArray *pageViews;

- (void)loadVisiblePages;
- (void)loadPage:(NSInteger)page;
- (void)purgePage:(NSInteger)page;
@end

@implementation PagedScrollViewController
@synthesize scrollView = _scrollView;
@synthesize pageControl = _pageControl;
@synthesize pageImages = _pageImages;
@synthesize pageViews = _pageViews;
@synthesize cancelButtonClicked = _cancelButtonClicked;
@synthesize headerTitle = _headerTitle;
@synthesize headerTitleS = _headerTitleS;
@synthesize caption = _caption;
@synthesize captionArray = _captionArray;

- (void)loadVisiblePages {
    // First, determine which page is currently visible
    CGFloat pageWidth = self.scrollView.frame.size.width;
    NSInteger page = (NSInteger)floor((self.scrollView.contentOffset.x * 2.0f + pageWidth) 
    / (pageWidth * 2.0f));

    // Update the page control
    self.pageControl.currentPage = page;

    NSObject *captionObject = [self.captionArray objectAtIndex:page];
    NSString *captionString = [NSString stringWithFormat:@"%@", [captionObject 
    valueForKey:@"caption"]]; 
    self.caption.text = captionString;

    // Work out which pages we want to load
    NSInteger firstPage = page - 1;
    NSInteger lastPage = page + 1;

    // Purge anything before the first page
    for (NSInteger i=0; i<firstPage; i++) {
        [self purgePage:i];
    }
        for (NSInteger i=firstPage; i<=lastPage; i++) {
        [self loadPage:i];
    }
    for (NSInteger i=lastPage+1; i<self.pageImages.count; i++) {
        [self purgePage:i];
    }
}

- (void)loadPage:(NSInteger)page {
    if (page < 0 || page >= self.pageImages.count) {
        // If it's outside the range of what we have to display, then do nothing
        return;
    }

    // Load an individual page, first seeing if we've already loaded it
    UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView == [NSNull null]) {
        CGRect frame = self.scrollView.bounds;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0.0f;

        UIImageView *newPageView = [[UIImageView alloc] initWithImage:[self.pageImages 
        objectAtIndex:page]];

        newPageView.contentMode  = UIViewContentModeScaleAspectFit;
        newPageView.frame = CGRectMake((page*320), 0, 310, 320);
        self.scrollView.maximumZoomScale = 1.3;
        self.scrollView.contentSize = CGSizeMake(320*[self.pageImages count],389);
        self.scrollView.frame = CGRectMake(320*(self.pageControl.currentPage), 44, 310, 
        370);
        [self.scrollView addSubview:newPageView];
        [self.pageViews replaceObjectAtIndex:page withObject:newPageView];
    }
 }

- (void)purgePage:(NSInteger)page {
 if (page < 0 || page >= self.pageImages.count) {
    // If it's outside the range of what we have to display, then do nothing
    return;
}

// Remove a page from the scroll view and reset the container array
UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView != [NSNull null]) {
        [pageView removeFromSuperview];
        [self.pageViews replaceObjectAtIndex:page withObject:[NSNull null]];
     }
 }

-(UIView *) viewForZoomingInScrollView:(UIScrollView *)scrollView {
      self.scrollView.contentSize = CGSizeMake(320*[self.pageImages count],389);
     return [self.scrollView.subviews objectAtIndex:self.pageControl.currentPage];
}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.scrollView.delegate = self;
    self.headerTitle.text = self.headerTitleS;
    // Set up the image we want to scroll & zoom and add it to the scroll view
    NSInteger pageCount = self.pageImages.count;

    // Set up the page control
    self.pageControl.currentPage = 0;
    self.pageControl.numberOfPages = pageCount;

    // Set up the array to hold the views for each page
    self.pageViews = [[NSMutableArray alloc] init];
    for (NSInteger i = 0; i < pageCount; ++i) {
    [self.pageViews addObject:[NSNull null]];
    }
}

- (void)viewWillAppear:(BOOL)animated {
   [super viewWillAppear:animated];
   // Load the initial set of pages that are on screen
   [self loadVisiblePages];
}

- (void)viewDidUnload {
   [super viewDidUnload];
   self.scrollView = nil;
   self.pageControl = nil;
   self.pageImages = nil;
   self.pageViews = nil;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  [self loadVisiblePages];
}

-(IBAction)cancelButtonClicked:(id)sender{
   [self dismissViewControllerAnimated:YES completion:nil];
}

@end

Answer 1

This is what I found to work. Supports multiple images with paging and zooming. Enjoy!

#define VIEW_FOR_ZOOM_TAG (1)

@implementation SVViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIScrollView *mainScrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    mainScrollView.pagingEnabled = YES;
    mainScrollView.showsHorizontalScrollIndicator = NO;
    mainScrollView.showsVerticalScrollIndicator = NO;

    CGRect innerScrollFrame = mainScrollView.bounds;

    for (NSInteger i = 0; i < 3; i++) {
    UIImageView *imageForZooming = [[UIImageView alloc] initWithImage:[UIImage imageNamed:  
    [NSString stringWithFormat:@"page%d", i + 1]]];
    imageForZooming.tag = VIEW_FOR_ZOOM_TAG;

    UIScrollView *pageScrollView = [[UIScrollView alloc] initWithFrame:innerScrollFrame];
    pageScrollView.minimumZoomScale = 1.0f;
    pageScrollView.maximumZoomScale = 2.0f;
    pageScrollView.zoomScale = 1.0f;
    pageScrollView.contentSize = imageForZooming.bounds.size;
    pageScrollView.delegate = self;
    pageScrollView.showsHorizontalScrollIndicator = NO;
    pageScrollView.showsVerticalScrollIndicator = NO;
    [pageScrollView addSubview:imageForZooming];

    [mainScrollView addSubview:pageScrollView];

    if (i < 2) {
        innerScrollFrame.origin.x += innerScrollFrame.size.width;
    }
    }

    mainScrollView.contentSize = CGSizeMake(innerScrollFrame.origin.x + 
    innerScrollFrame.size.width, mainScrollView.bounds.size.height);

    [self.view addSubview:mainScrollView];
   }

 - (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
  return [scrollView viewWithTag:VIEW_FOR_ZOOM_TAG];
}

 - (NSUInteger)supportedInterfaceOrientations {
 return UIInterfaceOrientationMaskPortrait;
} 

- (BOOL)shouldAutorotate {
 return NO;
}

@end