“This is my paging scroll view. There are many like it, but this one is mine.”
RGMPagingScrollView is a simple UIScrollView subclass that manages presentation of a single horizontal or vertical row of reusable views, similar to the Photos app on iOS. The API follows the patterns set by UITableView and UICollectionView which makes it easy to understand and use.
On iOS 6, UIPageViewController provides similar behaviour out of the box. I’ve made the source available for developers targeting older versions of iOS. I hope you find it useful.
See the example Xcode project in /RGMPagingScrollViewExample.
Instantiate RGMPagingScrollView in code or as part of a nib or storyboard. Set the datasource and delegate properties and adopt the corresponding protocols. Reusable views can be registered in advance using the -registerClass:forReuseIdentifier: or -registerNib:forReuseIdentifier: methods.
_pagingScrollView = [[RMGPagingScrollView alloc] initWithFrame:self.view.bounds]
_pagingScrollView.datasource = self;
_pagingScrollView.delegate = self;
[_pagingScrollView registerClass:[XYZPageView class] forReuseIdentifier:@"identifier"];
[self.view addSubview:_pagingScrollView];
Implement the two required methods, -pagingScrollViewNumberOfPages: and -pagingScrollView:viewForIndex:, which are analogous to those of UITableViewDatasource.
- (UIView *)pagingScrollView:(RGMPagingScrollView *)pagingScrollView viewForIndex:(NSInteger)idx
{
XYZPageView *view = (XYZPageView *)[pagingScrollView dequeueReusablePageWithIdentifer:@"identifier" forIndex:idx];
// customize view…
return view;
}
Following the behaviour of UITableView in iOS 5 and up, -dequeueReusablePageWithIdentifer: is guaranteed to return a view through reuse or by instantiating a new one from a registered class or nib.
The RGMPagingScrollViewDelegate protocol cleanly extends UIScrollViewDelegate. Thanks to the Objective-C runtime’s message forwarding system, any object that conforms to RGMPagingScrollViewDelegate will also receive any UIScrollViewDelegate method calls it can respond to.
There is one optional delegate method, -pagingScrollView:scrolledToPage:, which is called when the view finishes scrolling to a page boundary as a result of user action or explicit animation.
RGMPageControl is a customizable replacement for UIPageControl. It supports custom indicator images and spacing, and both horizontal and vertical layout.
_pageControl = [[RGMPageControl alloc] initWithItemImage:itemImage activeImage:activeImage];
_pageControl.numberOfPages = 3;
_pageControl.currentPage = 0;
[_pageControl addTarget:self action:@selector(pageControlValueChanged:) forControlEvents:UIControlEventValueChanged];
[self.view addSubview:_pageControl];
RGMPagingScrollView is provided as-is by Ryder Mackay. If you’re using it in a project, I’d love to hear about it on Twitter. If you’d like to contribute (thanks!), please send a pull request or open a new issue on GitHub.