tonyzonghui / ispagescrollview

A page scroll view which allows infinite scrolling (not looping). This scroll view is optimised for huge number of pages display.

ISPageScrollView

Note: This is a sub-project of UIKitHelper git project. You may want to use UIKitHelper in your project for more UIKit utilities.

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Description

ISPageScrollView is a UIScrollView subclass optimised for huge number of pages display. It uses lazy-loading mechanism to maintain only the previous few pages and the next few pages in order to minimize the memory usage.

Properties:

id<ISPageScrollViewDataSource> dataSource: Like UITableViewDataSource, it asks its dataSource object for views displayed in each page.

id<ISPageScrollViewDelegate> pageDelegate: Tells receiver when a page will be removed from cache, has been removed from cache or when the displayed page changed.

NSInteger numberOfReusablePages: number of pages maintanined in memory. This number should be an odd number (e.g: 5 = current displayed page + 2 pages in front + 2 pages after)

NSMutableDictionary readonly scrollViewAvailablePages: this is the dictionary that stores the views of the pages in memory. The keys for the dictionary are NSNumbers for page index. The values for each key is an UIView object.

DataSource required methods

*-viewForScrollView:(ISPageScrollView )scrollView page:(NSInteger)pageIndex: Needs to return the view to use on specified page.

*-numberOfPagesForPageScrollView:(ISPageScrollView )scrollView: Needs to return the number of pages in the scroll view.

Usage

It can be created in xcode like UIScollView or can be created programatically.

ISPageScrollView *pageScrollView = [[ISPageScrollView alloc] initWithFrame:CGRectMake(0, 0, 200, 100)];
pageScrollView.dataSource = self;
pageScrollView.numberOfReusableViews = 5;

[pageScrollView displayPage:0];

Also implement both methods of the datasource.

License

UIKitHelper is available under the MIT license. See the LICENSE file for more info.

ispagescrollview's Issues

NSRangeException - beyond bounds

When _numberOfPages and numberOfReusable views are equal, this raises an NSRangeException (beyond bounds). )I think in line 100 of ISPageScrollView:
NSInteger maxPageIndex = MIN(_numberOfPages, pageIndex + (_numberOfReusableViews - 1) / 2.0);

it should be

NSInteger maxPageIndex = MIN(_numberOfPages - 1, pageIndex + (_numberOfReusableViews - 1) / 2.0);