Working With Scroll Views

Transcript

1. Working with Scroll Views Ash Furrow Tuesday, 8 May, 12
2. What is a scroll view? • Subclass of UIView • A view which scrolls • Sometimes zooms Tuesday, 8 May, 12
3. What is a scroll view? • Subclass of UIView • A view which scrolls • Sometimes zooms UIView UIScrollView Tuesday, 8 May, 12
4. OK, what does “scroll” mean? • A container view that lets its subviews move around • Maps • Home screen • Table view • Most things that move in iOS Tuesday, 8 May, 12
5. How to UIScrollView Tuesday, 8 May, 12
6. How to UIScrollView • Create scroll view, either in xib or programmatically • Add subviews • ??? • Profit! Tuesday, 8 May, 12
7. How to UIScrollView • Create scroll view, either in xib or programmatically • Add subviews • ??? • Profit! • ʵ Set contentSize Tuesday, 8 May, 12
8. contentSize • Defines the scrollable region • CGSize • Large contentSize values don’t adversely affect performance Tuesday, 8 May, 12
9. contentInset Tuesday, 8 May, 12
10. contentOffset Tuesday, 8 May, 12
11. Demo: Basic Scroll View Tuesday, 8 May, 12
12. Scrolling • With Fingers! • Receive delegate callbacks (next slide) • Programmatically • to top • to new contentOffset • to new rectangle Tuesday, 8 May, 12
13. Interesting Properties • delaysContentTouches • scrollview gesture recognizers • bounces • alwaysBouncesVertical • alwaysBouncesHorizontal • scroll indicators (inset & style) • pagingEnabled Tuesday, 8 May, 12
14. Zooming • I am not an expert at zooming scroll views • Different approaches • Watch the WWDC videos Tuesday, 8 May, 12
15. UIScrollViewDelegate • Tracking • Dragging • Decelerating • Zooming • contentOffset change Tuesday, 8 May, 12
16. Demo: Paging Tuesday, 8 May, 12
17. YO, DAWG. I HEARD YOU LIKE SCROLLING. Tuesday, 8 May, 12
18. UITableViewDelegate • UITableView subclasses UIScrollView • Captures UIScrollViewDelegate callbacks Tuesday, 8 May, 12
19. Performance • UIScrollView Scales with subviews • Not with contentSize • UIImage will kill your memory footprint Tuesday, 8 May, 12
20. Delegate flowcharts • UIScrollViewDelegate is simple • Implementing complex behaviour with it is not Tuesday, 8 May, 12
21. Subclassing vs Delegation • Subclassing can break MVC • Better for repeated behaviours • Delegation can get verbose • You’re writing Objective-C, live with it Tuesday, 8 May, 12
22. Demo: Reusing Subviews Tuesday, 8 May, 12
23. Demo: Infinite Scroll Tuesday, 8 May, 12
24. Ash Furrow ash@ashfurrow.com @ashfurrow Podcast: DashDashForce.me http://ashfurrow.com/ScrollViewMaterials.zip Tuesday, 8 May, 12