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[英]How to use a for-in-loop to make multiple objects in a CADisplayLink
[英]How to generate an array of buttons using a for-in-loop and then animate them with a CADisplayLink
我試圖使用for-in-loop生成由10個按鈕組成的數組,然后使用CADisplayLink內的for-in-loop對它們進行動畫處理,但問題是僅創建了一個按鈕並對其進行了動畫處理。 請幫忙! 提前致謝!
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 - 1{
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 - 1{
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
}
}
構造函數Array(count:, repeatedValue:)
不會Array(count:, repeatedValue:)
執行UIButton
構造函數。 它接收一個值,然后重復該值,您碰巧在行中實例化了指針。
您所做的工作與以下功能相同:
var aButton:UIButton = UIButton.buttonWithType(.System) as UIButton
var buttons: [UIButton] = Array(count: 10, repeatedValue:aButton)
以這種方式拆分參數使Array
構造函數的操作更加清晰。
您可能想做的更像是:
var buttons:[UIButton] = Array()
for index in 1...10 {
buttons.append(UIButton.buttonWithType(.System) as UIButton)
}
您可能會變得更加敏捷:
var buttons:[UIButton] = Array(Range(1...10)).map( { $0; return UIButton.buttonWithType(UIButtonType.System) as UIButton } )
我不完全確定為什么需要增加$0;
到該關閉的最前面,但沒有它,它拒絕工作。 幸運的是,它什么也沒做。
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