如何使用 for-in-loop 在 CADisplayLink 中创建多个对象

Question

所以我尝试使用 for in 循环创建 10 个按钮，并使用 CADisplayLink 使所有这 10 个按钮向下移动。问题是我的 CADisplayLink 只向下移动一个按钮，我希望它移动所有 10 个按钮。请帮忙！提前致谢！

var button: UIButton!



override func viewDidLoad() {
    super.viewDidLoad()

    var displayLink = CADisplayLink(target: self, selector: "handleDisplayLink:")
    displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)

    for index in 0...10 {

        var xLocation:CGFloat = CGFloat(arc4random_uniform(300) + 30)

        button = UIButton.buttonWithType(UIButtonType.System) as UIButton

        button.frame = CGRectMake(xLocation, 10, 100, 100)
        button.setTitle("Test Button", forState: UIControlState.Normal)
        button.addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)

        self.view.addSubview(button)

        }



}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()

}

func handleDisplayLink(displayLink: CADisplayLink) {

    for index in 0...10 {

        var buttonFrame = button.frame
        buttonFrame.origin.y += 1
        button.frame = buttonFrame
        if button.frame.origin.y >= 500 {
            displayLink.invalidate()
        }
    }
}


func buttonAction(sender: UIButton) {
    sender.alpha = 0
}

}

Answer 1

您只获得了对您在 viewDidLoad 中创建的 10 个按钮之一的引用。使用类型为按钮 [UIButton] 的数组来存储所有 10 个，然后在 CADisplayLink 回调期间遍历它们中的每一个。

您的声明将是：

    var buttons: [UIButton] = Array(count: 10, repeatedValue: UIButton.buttonWithType(.System) as! UIButton)

无论何时您在原始代码中引用了按钮，请使用数组索引运算符在 for 循环的当前索引处引用该按钮：

buttons[index]

这里有 Swift 数组的概述和标准库参考：

• Swift Language Guide: Collection Types
• Swift Standard Library Reference: Arrays

所以提供的代码是：

var buttons: [UIButton] = Array(count: 10, repeatedValue: UIButton.buttonWithType(.System) as! UIButton)

override func viewDidLoad() {
    super.viewDidLoad()

    var displayLink = CADisplayLink(target: self, selector: "handleDisplayLink:")
    displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)

    for index in 0...10 {

        var xLocation:CGFloat = CGFloat(arc4random_uniform(300) + 30)

        buttons[index].frame = CGRectMake(xLocation, 10, 100, 100)
        buttons[index].setTitle("Test Button \(index)", forState: UIControlState.Normal)
        buttons[index].addTarget(self, action: "buttonAction:", forControlEvents: UIControlEvents.TouchUpInside)

        self.view.addSubview(buttons[index])

        }



}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()

}

func handleDisplayLink(displayLink: CADisplayLink) {

    for index in 0...10 {

        var buttonFrame = buttons[index].frame
        buttonFrame.origin.y += 1
        buttons[index].frame = buttonFrame
        if buttons[index].frame.origin.y >= 500 {
            displayLink.invalidate()
        }
    }
}


func buttonAction(sender: UIButton) {
    sender.alpha = 0
}