显示一个字母在与延迟

Question

时间我试图在同一时间显示在textView，一个字母，并用延迟，但我无法得到它的权利。

我希望它看起来像某人正在输入它。以下是我当前的代码：

let delay = 2.0 * Double(NSEC_PER_SEC) 
let dispatchTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay)) 

let localmessage = message + "\n" 

for letter in localmessage.characters { 
     dispatch_after(dispatchTime, dispatch_get_main_queue(), { 
      self.textView.text = self.textView.text + String(letter) 

     }) 

    } 

Answer 1

您正在使用相同的dispatchTime，因此所有字符都将同时显示。您需要增加for循环中的dispatchTime以逐个显示一个字符。

试试这样说：

let localmessage = message + "\n" 

var myInt = 1 

for letter in localmessage.characters { 

    let delay = 2.0 * Double(NSEC_PER_SEC) * Double(myInt) 
    let dispatchTime = dispatch_time(DISPATCH_TIME_NOW, Int64(delay)) 

    dispatch_after(dispatchTime, dispatch_get_main_queue(), { 
     self.textView.text = self.textView.text + String(letter) 
    }) 

    myInt = myInt + 1 
} 

Answer 2

您可以尝试使用的NSTimer，而不是GCD：

var index = 0 
var timer = NSTimer() 

    override func viewDidLoad() { 
     super.viewDidLoad() 

     timer.scheduledTimerWithTimeInterval(2.0, target: self, selector: #selector(ViewController.updateTextView), userInfo: nil, repeats: true) 

    } 

    func updateTextView() { 

     let letter = localmessage.characters[index] 

     self.textView.text = self.textView.text + String(letter) 

     index++ 
     if index == localmessage.characters.count { 
      timer.invalidate() 
     } 

    } 

Answer 3

下面是我会做

let message = "hello world" 
    var index:Double = 1.0 
    let delayInSeconds = 0.5 
    for letter in message.characters { 
     runAfterDelay(delayInSeconds * index, block: { 
      self.firstTextField.text = self.firstTextField.text! + String(letter) 
     }) 
     index = index + 1 
    } 
} 

func runAfterDelay(delay: NSTimeInterval, block: dispatch_block_t) { 
    let time = dispatch_time(DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC))) 
    dispatch_after(time, dispatch_get_main_queue(), block) 
} 

的runAfterDelay功能验证在很多情况下非常方便，所以我喜欢保持它:)

Answer 4

为什么不简单地使用计时器？

class ViewController: UIViewController { 

    @IBOutlet weak var textView: UITextView! 

    let message = "Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. Nam liber te conscient to factor tum poen legum odioque civiuda." 

    override func viewDidLoad() { 
     super.viewDidLoad() 
     self.typingTimer() 
    } 

    func typingTimer() { 
     var localMessage = message 
     Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true, block: { timer in 
      if localMessage.characters.count > 0 { 
       self.textView.text.append(localMessage.characters.remove(at: localMessage.characters.startIndex)) 
      } else { 
       timer.invalidate() 
      } 
     }) 
    } 

}