Ios 在Swift中制作一个简单的淡入动画？

我正在尝试用Swift制作一个简单的动画。这是一种淡入

我尝试过：

self.myFirstLabel.alpha = 0
self.myFirstButton.alpha = 0
self.mySecondButton.alpha = 0

// fadeIn() - always animates to alpha = 1.0
yourView.fadeIn()     // uses default duration of 0.3
yourView.fadeIn(1.0)  // uses custom duration (1.0 in this example)

// fadeOut() - always animates to alpha = 0.0
yourView.fadeOut()    // uses default duration of 0.3
yourView.fadeOut(1.0) // uses custom duration (1.0 in this example)

// fadeTo() - used if you want a custom alpha value
yourView.fadeTo(0.5)  // uses default duration of 0.3
yourView.fadeTo(0.5, duration: 1.0)

那么，我有：

self.view.addSubview(myFirstLabel)
self.view.addSubview(myFirstButton)
self.view.addSubview(mySecondButton)

然后：

UIView.animateWithDuration(1.5, animations: {
 self.myFirstLabel.alpha = 1.0
 self.myFirstButton.alpha = 1.0
 self.mySecondButton.alpha = 1.0
})

我的viewDidLoad函数中包含了所有这些功能。

---

我该怎么做

问题在于，您尝试在视图控制器的生命周期中过早启动动画。在

viewDidLoad

中，视图刚刚创建，尚未添加到视图层次结构中，因此此时尝试设置其

子视图之一的动画将产生不良结果

您真正应该做的是继续在
viewdiload
（或创建视图的位置）中设置视图的alpha，然后等待调用
viewdilease
：方法。此时，您可以毫无问题地启动动画

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    UIView.animate(withDuration: 1.5) {
        self.myFirstLabel.alpha = 1.0
        self.myFirstButton.alpha = 1.0
        self.mySecondButton.alpha = 1.0
    }
}

0x7ffffff的答案是肯定的，而且绝对详尽无遗

另外，我建议您通过以下方式进行UIView扩展：

public extension UIView {

  /**
  Fade in a view with a duration

  - parameter duration: custom animation duration
  */
  func fadeIn(duration duration: NSTimeInterval = 1.0) {
    UIView.animateWithDuration(duration, animations: {
        self.alpha = 1.0
    })
  }

  /**
  Fade out a view with a duration

  - parameter duration: custom animation duration
  */
  func fadeOut(duration duration: NSTimeInterval = 1.0) {
    UIView.animateWithDuration(duration, animations: {
        self.alpha = 0.0
    })
  }

}

Swift-3

/// Fade in a view with a duration
/// 
/// Parameter duration: custom animation duration
func fadeIn(withDuration duration: TimeInterval = 1.0) {
    UIView.animate(withDuration: duration, animations: {
        self.alpha = 1.0
    })
}

/// Fade out a view with a duration
///
/// - Parameter duration: custom animation duration
func fadeOut(withDuration duration: TimeInterval = 1.0) {
    UIView.animate(withDuration: duration, animations: {
        self.alpha = 0.0
    })
}

Swift-5

public extension UIView {

/**
 Fade in a view with a duration
 
 - parameter duration: custom animation duration
 */
 func fadeIn(duration: TimeInterval = 1.0) {
     UIView.animate(withDuration: duration, animations: {
        self.alpha = 1.0
     })
 }

/**
 Fade out a view with a duration
 
 - parameter duration: custom animation duration
 */
func fadeOut(duration: TimeInterval = 1.0) {
    UIView.animate(withDuration: duration, animations: {
        self.alpha = 0.0
    })
  }

}

通过这种方式，您可以在代码中的任何位置执行此操作：

let newImage = UIImage(named: "")
newImage.alpha = 0 // or newImage.fadeOut(duration: 0.0)
self.view.addSubview(newImage)
... 
newImage.fadeIn()

代码重用很重要
 Swift唯一解决方案

与之类似，我使用
UIView
扩展名。与他的解决方案相比，我使用
DispatchQueue.main.async
来确保动画在主线程上完成，
alpha
参数用于淡入特定值，可选
持续时间
参数用于更干净的代码

extension UIView {
  func fadeTo(_ alpha: CGFloat, duration: TimeInterval = 0.3) {
    DispatchQueue.main.async {
      UIView.animate(withDuration: duration) {
        self.alpha = alpha
      }
    }
  }

  func fadeIn(_ duration: TimeInterval = 0.3) {
    fadeTo(1.0, duration: duration)
  }

  func fadeOut(_ duration: TimeInterval = 0.3) {
    fadeTo(0.0, duration: duration)
  }
}

如何使用它：

self.myFirstLabel.alpha = 0
self.myFirstButton.alpha = 0
self.mySecondButton.alpha = 0

// fadeIn() - always animates to alpha = 1.0
yourView.fadeIn()     // uses default duration of 0.3
yourView.fadeIn(1.0)  // uses custom duration (1.0 in this example)

// fadeOut() - always animates to alpha = 0.0
yourView.fadeOut()    // uses default duration of 0.3
yourView.fadeOut(1.0) // uses custom duration (1.0 in this example)

// fadeTo() - used if you want a custom alpha value
yourView.fadeTo(0.5)  // uses default duration of 0.3
yourView.fadeTo(0.5, duration: 1.0)

如果您想要可重复的淡入淡出动画，可以使用
CABasicAnimation
如下所示：

首先创建视图扩展：
如何使用它：
斯威夫特5
其他答案是正确的，但就我而言，我还需要处理其他属性（
alpha
，
animate
，
completion
）。因此，我对这些参数进行了一些修改，如下所示：

extension UIView {
    /// Helper function to update view's alpha with animation
    /// - Parameter alpha: View's alpha
    /// - Parameter animate: Indicate alpha changing with animation or not
    /// - Parameter duration: Indicate time for animation
    /// - Parameter completion: Completion block after alpha changing is finished
    func set(alpha: CGFloat, animate: Bool, duration: TimeInterval = 0.3, completion: ((Bool) -> Void)? = nil) {
        let animation = { (view: UIView) in
            view.alpha = alpha
        }
    
        if animate {
            UIView.animate(withDuration: duration, animations: {
                animation(self)
            }, completion: { finished in
                completion?(finished)
            })
        } else {
            layer.removeAllAnimations()
            animation(self)
            completion?(true)
        }
    }
}

所有元素同时进入。视图加载时正确。您确定视图在xib中正确连接吗？我没有使用IB。一切都是编程的。从您提供的代码来看，一切都应该正常工作（这与Swift无关）。在其他地方必须有一个错误。考虑将视图外观方法调用移动到<代码> VIEWLVIEW 或 VIEWDIDENTUCTION/CODE >，因为您不知道加载和显示视图之间会发生什么。<代码> VIEWS会出现< /代码>更适合这个吗？记住，如果您只有1个语句，您需要添加一个return
UIView.animateWithDuration（1.5，animations:{self.myFirstLabel.alpha=1.0 return}）
@oshevans您指的是需要在闭包末尾添加return语句吗？这在最新的Xcode版本中得到了很大的修正，我有一个非常类似的错误。请看你是否能帮我：@0x7fffffff'…基本上已修复…'-听起来不太有希望；/尚未从6.2更新
extension UIView {
    /// Helper function to update view's alpha with animation
    /// - Parameter alpha: View's alpha
    /// - Parameter animate: Indicate alpha changing with animation or not
    /// - Parameter duration: Indicate time for animation
    /// - Parameter completion: Completion block after alpha changing is finished
    func set(alpha: CGFloat, animate: Bool, duration: TimeInterval = 0.3, completion: ((Bool) -> Void)? = nil) {
        let animation = { (view: UIView) in
            view.alpha = alpha
        }
    
        if animate {
            UIView.animate(withDuration: duration, animations: {
                animation(self)
            }, completion: { finished in
                completion?(finished)
            })
        } else {
            layer.removeAllAnimations()
            animation(self)
            completion?(true)
        }
    }
}