photoview using UIScrollViewController

Question

I'm trying to make photo album like photo.app in iPhone. I know We have 'PhotoScroller' example from Apple (which I don't think I can copy and paste the code here due to the Non Disclosure Agreement, plus it's bit biggy to play with at the moment). However I found an another example from random search and it seems like based on the PhotoScroller (very simplified tough). The link for the example is ; http://ykyuen.wordpress.com/2010/05/22/iphone-uiscrollview-with-paging-example/

I applied this code to my project to make photo album (and it scrolls, at least), but I found a problem. The problem is I cannot start from the page I want. The sample code only starts scrolling with Page One. Code itself seems 'really' simple but somehow I just cannot make it start from the page I choose.

Here is main part of the sample code that I found on the Internet. You can of course download the project the link above.

- (void)viewDidLoad {

NSLog(@"ScrollViewWithPagingViewContrller :: viewDidLoad"); [super viewDidLoad];

// view controllers are created lazily // in the meantime, load the array with placeholders which will be replaced on demand NSMutableArray *controllers = [[NSMutableArray alloc] init]; for (unsigned i = 0; i < kNumberOfPages; i++) { [controllers addObject:[NSNull null]]; } self.viewControllers = controllers; [controllers release];

// a page is the width of the scroll view
scrollView.pagingEnabled = YES;
scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * kNumberOfPages, scrollView.frame.size.height);
scrollView.showsHorizontalScrollIndicator = NO;
scrollView.showsVerticalScrollIndicator = NO;
scrollView.scrollsToTop = NO;
scrollView.delegate = self;

pageControl.numberOfPages = kNumberOfPages;
pageControl.currentPage = 0;

// pages are created on demand
// load the visible page
// load the page on either side to avoid flashes when the user starts scrolling
[self loadScrollViewWithPage:0];
[self loadScrollViewWithPage:1];}

- (void)loadScrollViewWithPage:(int)page {

NSLog(@"ScrollViewWithPagingViewContrller :: loadScrollViewWithPage"); if (page < 0) return; if (page >= kNumberOfPages) return;

// replace the placeholder if necessary


MyViewController *controller = [viewControllers objectAtIndex:page];
if ((NSNull *)controller == [NSNull null]) {
    controller = [[MyViewController alloc] initWithPageNumber:page];
    [viewControllers replaceObjectAtIndex:page withObject:controller];
  //

[controller release]; }

// add the controller's view to the scroll view
if (nil == controller.view.superview) {
    CGRect frame = scrollView.frame;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0;
    controller.view.frame = frame;
    [scrollView addSubview:controller.view];
}

}

- (void)scrollViewDidScroll:(UIScrollView *)sender {

NSLog(@"ScrollViewWithPagingViewContrller :: scrollViewDidScroll");

// We don't want a "feedback loop" between the UIPageControl and the scroll delegate in
// which a scroll event generated from the user hitting the page control triggers updates from
// the delegate method. We use a boolean to disable the delegate logic when the page control is used.
if (pageControlUsed) {
    // do nothing - the scroll was initiated from the page control, not the user dragging
    return;
}

// Switch the indicator when more than 50% of the previous/next page is visible
CGFloat pageWidth = scrollView.frame.size.width;

int page = floor(scrollView.contentOffset.x - pageWidth / 2) / pageWidth; pageControl.currentPage = page;

// load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
[self loadScrollViewWithPage:page - 1];
[self loadScrollViewWithPage:page];
[self loadScrollViewWithPage:page + 1];

// A possible optimization would be to unload the views+controllers which are no longer visible

}

// At the begin of scroll dragging, reset the boolean used when scrolls originate from the UIPageControl

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView { NSLog(@"ScrollViewWithPagingViewContrller :: scrollViewWillBeginDragging"); pageControlUsed = NO; }

    // At the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { NSLog(@"ScrollViewWithPagingViewContrller :: scrollViewDidEndDecelerating"); pageControlUsed = NO; }

- (IBAction)changePage:(id)sender {

NSLog(@"ScrollViewWithPagingViewContrller :: changePage"); int page = pageControl.currentPage;

// load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
[self loadScrollViewWithPage:page - 1];
[self loadScrollViewWithPage:page];
[self loadScrollViewWithPage:page + 1];

// update the scroll view to the appropriate page CGRect frame = scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; [scrollView scrollRectToVisible:frame animated:YES];

// Set the boolean used when scrolls originate from the UIPageControl. See scrollViewDidScroll: above. pageControlUsed = YES; }

Warrior Warrior · Accepted Answer · 2010-12-15T11:47:20

I have implemented photo album view where in first view i have shown all the thumbnail images and on clicking each image it gives its full screen view. you also scroo the images. See this answer.

All the best.

photoview using UIScrollViewController

2 Answers