在 swift 2.0 中一次显示一个字符

Question

Swift2.0 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个字符的消息。

我写了这个，它有效，但我忍不住不能用 CALayers 做一些事情，也许 and/or alpha 值？或者一些动画小发明，更 swift 有价值的东西；这感觉和看起来有点笨重，真的是 1977 年的那种。

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

我认为 Swiftworthy 是主观的，但这是另一个基于您的代码当前工作方式的实现，它将 NSTimer 包装在 Swift class.

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
        }
    }
}

在 swift 2.0 中一次显示一个字符

Displaying text one character at a time in swift 2.0

uitextview

uiview

nsattributedstring

ios

swift