UIButton 之外的 TouchUpInside 边界

Question

我目前正在努力熟悉 Swift 下的 UIKit，并找出以编程方式添加 UI 元素的最佳方法。但是，我发现触摸可以在它开始的按钮之外结束，但仍注册为 TouchUpInside 事件。下面的 ViewController 来自单个视图应用程序，可以直接在按钮 17 上开始触摸，在按钮 18 上结束触摸，并且仍然让 buttonAction() 声明“Button tapped: 17”。

知道我在这里缺少什么吗？ （编辑：这是在 Xcode 6 beta 3 BTW 下。）

// ViewController.swift

import UIKit

class ViewController: UIViewController {
    let scrollView:UIScrollView = UIScrollView()

    var GWIDTH:Float = 0.0
    var GHEIGHT:Float = 0.0


    override func viewDidLoad() {
        super.viewDidLoad()

        GWIDTH = self.view.bounds.size.width
        GHEIGHT = self.view.bounds.size.height

        scrollView.frame = CGRectMake(10, 10, GWIDTH-10, GHEIGHT-20)
        scrollView.contentSize = CGSize(width:GWIDTH-20, height: 0)
        self.view.addSubview(scrollView)

        for currentTag in 1...30{
            var currentButton = UIButton.buttonWithType(UIButtonType.System) as UIButton
            currentButton.frame = CGRectMake(100, scrollView.contentSize.height, 100, 50)
            currentButton.backgroundColor = UIColor.greenColor()
            currentButton.setTitle("Test Button \(currentTag)", forState: UIControlState.Normal)
            currentButton.tag = currentTag
            currentButton.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)

            scrollView.addSubview(currentButton)
            scrollView.contentSize = CGSize(width:GWIDTH-20,height:2.0+currentButton.frame.size.height+currentButton.frame.origin.y)
        }//next
    }// end viewDidLoad()


    func buttonAction(sender:UIButton!){
        println("Button tapped: \(sender.tag)")
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


    override func prefersStatusBarHidden() -> Bool {
        return true
    }
}

Answer 1

好吧，这需要一些挖掘才能深入了解，但有几个有用的 Obj-C 链接...

UIControlEventTouchDragExit triggers when 100 pixels away from UIButton

How to correctly subclass UIControl?

http://www.bytearray.org/?p=5336（尤其是第 89 行）

...由于触摸界面，这种行为似乎是标准的（我个人本能地发现默认区域过多，但我确信 Apple 做了功课）并且可以通过子类化 UIControl 或询问来覆盖控制事件的位置。

我选择了后者，这里有一个专门在 Swift 中的实现：

// ViewController.swift

import UIKit

class ViewController: UIViewController {
    let buttonCount = 3

    override func viewDidLoad() {
        super.viewDidLoad()

        for currentTag:Int in 1...buttonCount{
            var currentButton = UIButton.buttonWithType(UIButtonType.System) as UIButton
            currentButton.frame = CGRectMake(50, Float(currentTag*50), 120, 50)
            currentButton.backgroundColor = UIColor.greenColor()
            currentButton.setTitle("Test Button \(currentTag)", forState: UIControlState.Normal)
            currentButton.contentEdgeInsets = UIEdgeInsets(top:3,left:6,bottom:3,right:6)
            currentButton.tag = currentTag
            currentButton.addTarget(self,
                action: "btn_TouchDown:",
                forControlEvents: UIControlEvents.TouchDown)
            currentButton.addTarget(self,
                action: "btn_TouchDragExit:",
                forControlEvents: UIControlEvents.TouchDragExit)
            currentButton.addTarget(self,
                action: "btn_TouchUpInside:event:",
                forControlEvents: UIControlEvents.TouchUpInside)
            currentButton.sizeToFit()

            self.view.addSubview(currentButton)
        }//next
    }// end viewDidLoad()


    func btn_TouchDown(sender:UIButton!){
        println("TouchDown event: \(sender.tag)\n")
    }

    func btn_TouchDragExit(sender:UIButton!){
        println("TouchDragExit event: \(sender.tag)\n")
    }

    func btn_TouchUpInside(sender:UIButton!,event:UIEvent!){
        println("TouchUpInside event: \(sender.tag)")

        var currentTouch:CGPoint = event.allTouches().anyObject().locationInView(sender)
        println( "Point: \(currentTouch.x), \(currentTouch.y)\n" )
        if currentTouch.x > sender.frame.width{return}
        if currentTouch.x < 0 {return}
        if currentTouch.y > sender.frame.height{return}
        if currentTouch.y < 0 {return}

        println("Event ended within frame!")
    }


    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


    override func prefersStatusBarHidden() -> Bool {
        return true
    }
}