Working With Scroll Views

Transcript

1. Working with
   Scroll Views
   Ash Furrow
   Tuesday, 8 May, 12
   

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2. What is a scroll view?
   • Subclass of UIView
   • A view which scrolls
   • Sometimes zooms
   Tuesday, 8 May, 12
   

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3. What is a scroll view?
   • Subclass of UIView
   • A view which scrolls
   • Sometimes zooms
   UIView
   UIScrollView
   Tuesday, 8 May, 12
   

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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
   

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

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