Modern User Interaction on iOS - 笔记

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WWDC 2017 Session 219 地址：[https://developer.apple.com/videos/play/wwdc2017/219/

目录：

  • 手势 The UIGestureRecognizer system
  • 系统手势 System gesture interaction
  • 拖拽 Drag and Drop

1. 手势

基础：

  • UIGestureRecognizer 比 UITouch 优先级高

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    class UIGestureRecognizer: NSObject {
        open var delaysTouchesEnded: Bool // default is true.
        open var cancelsTouchesInView: Bool // default is true.
        open var delaysTouchesBegan: Bool // default is false.
    }

    ​

  • UIGestureRecognizer 只有一个的胜出相应手势

  • UIGestureRecognizer 是否允许同时响应其他手势：在delegate可控制

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    public protocol UIGestureRecognizerDelegate: NSObjectProtocol {
           
           optional func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool
           
       }

    ​

  • UIGestureRecognizer 是否让其他手势失效

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    open class UIGestureRecognizer: NSObject {
        open func shouldRequireFailure(of otherGestureRecognizer: UIGestureRecognizer) -> Bool
        open func shouldBeRequiredToFail(by otherGestureRecognizer: UIGestureRecognizer) -> Bool
    }

  • Hit Testing

  • 新属性 name，便于调试

手势系统的注意事项：

  • 复查你的构建步骤（Revisit your setups ）
  • 排除和失效的标准（Exclusion and failure requirements）
  • 手势是否在正确的视图上？（ Are your gesture recognizers on the right views?）

2. 系统手势

应用手势和系统手势之争！如非沉浸式的游戏或画画的应用，别推迟系统手势。

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class MyViewController: UIViewController {
    
    // override to return which screen edges to defer system gestures
    override func preferredScreenEdgesDeferringSystemGestures() -> UIRectEdge {
        return deferControlCenter ? .bottom : UIRectEdge()
    }
    
    // call whenever your method would return a different screen edge
    var deferControlCenter: Bool {
        didSet { setNeedsUpdateOfScreenEdgesDeferringSystemGestures() }
    }
    
}

3. 拖拽

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let dragInteraction = UIDragInteraction(delegate: myDelegate) myView.addInteraction(dragInteraction)

总结

手势部分关于同时兼容或禁止其他的应该都很熟悉，尤其是分页加 table view经常处理。iOS可以延迟系统边缘手势很不错的选择，很多app手势经常与系统同步调出。拖拽的话，主要在iPad上应用，就不深入学习了。