ios - 我将如何从一系列不同的单词或句子中淡入和淡出？

Question

所以我已经在 Swift 中为标签动画构建了淡入淡出。但我想从一系列不同的句子中淡入和淡出，因此每次淡入和淡出时，都会是不同的五线谱。

   override func viewDidLoad()
    {
        super.viewDidLoad()
         label.alpha = 0
        animatedText()

     }
  func animatedText(){
        UIView.animateWithDuration(2.0, animations: {
            self.label.alpha = 1.0

            }, completion: {
                (Completed: Bool) -> Void in

                UIView.animateWithDuration(1.0, delay: 2.0, options: UIViewAnimationOptions.CurveLinear, animations: {
                    self.label.alpha = 0
                    }, completion: {
                         (Completed: Bool) -> Void in

                        self.animatedText()
                })
        })
    }

Answer 1

尝试这个功能:

class ViewController: UIViewController {

  @IBOutlet weak var label1: UILabel!
  @IBOutlet weak var label2: UILabel!

  var sentences = ["The cat sat.", "The rhino ate.", "The monkey laughed", "The zebra ran.", "The fish swam", "The potato grew."]
  override func viewDidLoad() {
    super.viewDidLoad()
    label1.text = sentences[0]
    label2.text = sentences[1]
    label1.alpha = 1.0
    label2.alpha = 0.0

  }
  var counter = 1

  @IBAction func animateBtnPressed(_ sender: UIButton) {
    fadeText(counter: &counter, duration: 2.0)
  }


  func fadeText(counter: inout Int, duration: TimeInterval) {
    if counter < sentences.count {
      if counter % 2 != 0 {
        UIView.animate(withDuration: duration, animations: {
          self.label1.alpha = 0.0
          self.label2.alpha = 1.0          
        }, completion: { finished in
          if finished {
            counter += 1
            if counter <= (self.sentences.count - 1) {
              self.label1.text = self.sentences[counter]
            } else {
              return
            }
            self.fadeText(counter: &counter, duration: duration)
          }
        })
      } else {
        UIView.animate(withDuration: duration, animations: {
          self.label1.alpha = 1.0
          self.label2.alpha = 0.0
        }, completion: { finished in
          if finished {
            counter += 1
            if counter <= (self.sentences.count - 1) {
              self.label2.text = self.sentences[counter]
            } else {
              return
            }
            self.fadeText(counter: &counter, duration: duration)
          }
        })
      }
    }
  }
}

假设:

1. 有一个名为 sentences 的数组(您可以更改此设置)在ViewController上其中包含 String
2. 有一个counter 从 1 开始 的变量
3. UILabel Storyboard中的 s 重叠。

除此之外，您只需使用 counter 调用该函数即可带有 & 的变量前面的运算符，因为 fadeText更改 counter变量它需要内存中 counter 的地址变量，而不是值(请注意 inout 参数中的 fadeText )。

如果您有任何疑问，请随时提问!