在Swift 2.0中一次显示一个字符

Question

Swift 2.0的新功能；尝试学习它，对动画感兴趣，并尝试编写一些代码以一次在屏幕上显示一条消息。

我写了这个，它可以工作，但是我不能帮忙，但是我可能无法对CALayers和/或alpha值做些什么？或一些动画小玩意，更值得一去；这感觉和看起来有点笨拙，确实在1977年。

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.


let supertext  = "A long time ago, in a galaxy far, far away ..."
let round = supertext.characters.count
for i in 0...round {
    let delay = Double(i)/10
    let subtext = supertext[supertext.startIndex..<supertext.startIndex.advancedBy(i)]
    NSTimer.scheduledTimerWithTimeInterval(delay, target: self, selector: "ghostText:", userInfo: ["theText" :subtext], repeats: false)
    }
}

var view3:UITextView = UITextView()

func ghostText(timer:NSTimer) {
    view3.removeFromSuperview()
    let userInfo = timer.userInfo as! Dictionary<String, AnyObject>
    let tempText:NSString = (userInfo["theText"] as! NSString)
    print(tempText)

    let font = UIFont(name: "Georgia", size: 18.0) ?? UIFont.systemFontOfSize(18.0)
    let textFont = [NSFontAttributeName:font]

    let subChararacter = NSAttributedString(string: String(tempText), attributes: textFont)
    view3.frame = CGRect(x: 100, y: 120, width: CGRectGetWidth(self.view.frame), height: CGRectGetWidth(self.view.frame)-20)
    view3.attributedText = subChararacter
    self.view.addSubview(view3)
}

Answer 1

我想Swiftworthy是主观的，但这是另一个基于您代码当前工作方式的实现，该实现将NSTimer包装在Swift类中。

class Timer {
    typealias TimerFunction = (Int)->Bool
    private var handler: TimerFunction
    private var i = 0

    init(interval: NSTimeInterval, handler: TimerFunction) {
        self.handler = handler
        NSTimer.scheduledTimerWithTimeInterval(interval, target: self, selector: "timerFired:", userInfo: nil, repeats: true)
    }

    @objc
    private func timerFired(timer:NSTimer) {
        if !handler(i++) {
            timer.invalidate()
        }
    }
}

class ViewController: UIViewController {
    let text: NSAttributedString = {
        let font = UIFont(name: "Georgia", size: 18.0) ?? UIFont.systemFontOfSize(18.0)
        return NSAttributedString(string: "A long time ago, in a galaxy far, far away ...", attributes: [NSFontAttributeName: font])
    }()

    override func viewDidLoad() {
        super.viewDidLoad()

        let textView = UITextView(frame: CGRect(x: 100, y: 120, width: CGRectGetWidth(self.view.frame), height: CGRectGetWidth(self.view.frame)-20))
        self.view.addSubview(textView)

        let _ = Timer(interval: 0.1) {i -> Bool in
            textView.attributedText = self.text.attributedSubstringFromRange(NSRange(location: 0, length: i+1))
            return i + 1 < self.text.string.characters.count
        }
    }
}