UILabel中的动画文本更改

我正在将新的文本值设置为UILabel。目前，新文本看起来很好。但是，我想在出现新文本时添加一些动画。我想知道如何为新文本的外观设置动画。

我想知道它是否有效，并且完美！

目标C

[UIView transitionWithView:self.label 
                  duration:0.25f 
                   options:UIViewAnimationOptionTransitionCrossDissolve 
                animations:^{

    self.label.text = rand() % 2 ? @"Nice nice!" : @"Well done!";

  } completion:nil];

斯威夫特3，4，5

UIView.transition(with: label,
              duration: 0.25,
               options: .transitionCrossDissolve,
            animations: { [weak self] in
                self?.label.text = (arc4random()() % 2 == 0) ? "One" : "Two"
         }, completion: nil)

目标C

为了实现真正的交叉溶解过渡（旧标签淡入，新标签淡入），您不希望淡入淡出。即使文本未更改，也可能导致不必要的闪烁。

请改用这种方法：

CATransition *animation = [CATransition animation];
animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
animation.type = kCATransitionFade;
animation.duration = 0.75;
[aLabel.layer addAnimation:animation forKey:@"kCATransitionFade"];

// This will fade:
aLabel.text = "New"

另请参见： 对两个数字之间的UILabel文本进行动画处理？

在iOS 10、9、8中的演示：

已在iOS 10到8.0上使用Xcode 8.2.1和7.1，ObjectiveC测试过。

►要下载完整项目，请在Swift Recipes中搜索SO-3073520。

斯威夫特4

淡化UILabel（或与此有关的任何UIView）的正确方法是使用Core Animation Transition。如果内容不变，则不会闪烁，也不会褪色为黑色。

便携式且干净的解决方案是使用Extensionin Swift（在更改可见元素之前调用）

// Usage: insert view.fadeTransition right before changing content


extension UIView {
    func fadeTransition(_ duration:CFTimeInterval) {
        let animation = CATransition()
        animation.timingFunction = CAMediaTimingFunction(name:
            CAMediaTimingFunctionName.easeInEaseOut)
        animation.type = CATransitionType.fade
        animation.duration = duration
        layer.add(animation, forKey: CATransitionType.fade.rawValue)
    }
}

调用看起来像这样：

// This will fade
aLabel.fadeTransition(0.4)
aLabel.text = "text"

►在GitHub上找到此解决方案，在Swift Recipes上找到其他详细信息。

从iOS4开始，显然可以使用块来完成：

[UIView animateWithDuration:1.0
                 animations:^{
                     label.alpha = 0.0f;
                     label.text = newText;
                     label.alpha = 1.0f;
                 }];

这是使此工作有效的代码。

[UIView beginAnimations:@"animateText" context:nil];
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationDuration:1.0f];
[self.lbl setAlpha:0];
[self.lbl setText:@"New Text";
[self.lbl setAlpha:1];
[UIView commitAnimations];

UILabel扩展解决方案

extension UILabel{

  func animation(typing value:String,duration: Double){
    let characters = value.map { $0 }
    var index = 0
    Timer.scheduledTimer(withTimeInterval: duration, repeats: true, block: { [weak self] timer in
        if index < value.count {
            let char = characters[index]
            self?.text! += "\(char)"
            index += 1
        } else {
            timer.invalidate()
        }
    })
  }


  func textWithAnimation(text:String,duration:CFTimeInterval){
    fadeTransition(duration)
    self.text = text
  }

  //followed from @Chris and @winnie-ru
  func fadeTransition(_ duration:CFTimeInterval) {
    let animation = CATransition()
    animation.timingFunction = CAMediaTimingFunction(name:
        CAMediaTimingFunctionName.easeInEaseOut)
    animation.type = CATransitionType.fade
    animation.duration = duration
    layer.add(animation, forKey: CATransitionType.fade.rawValue)
  }

}

简称函数

uiLabel.textWithAnimation(text: "text you want to replace", duration: 0.2)

谢谢你们的所有提示。希望这对长期有帮助

上面的SwiftArchitect解决方案的Swift 4.2版本（效果很好）：

    // Usage: insert view.fadeTransition right before changing content    

extension UIView {

        func fadeTransition(_ duration:CFTimeInterval) {
            let animation = CATransition()
            animation.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
            animation.type = CATransitionType.fade
            animation.duration = duration
            layer.add(animation, forKey: CATransitionType.fade.rawValue)
        }
    }

调用：

    // This will fade

aLabel.fadeTransition(0.4)
aLabel.text = "text"

Swift 2.0：

UIView.transitionWithView(self.view, duration: 1.0, options: UIViewAnimationOptions.TransitionCrossDissolve, animations: {
    self.sampleLabel.text = "Animation Fade1"
    }, completion: { (finished: Bool) -> () in
        self.sampleLabel.text = "Animation Fade - 34"
})

要么

UIView.animateWithDuration(0.2, animations: {
    self.sampleLabel.alpha = 1
}, completion: {
    (value: Bool) in
    self.sampleLabel.alpha = 0.2
})

使用Swift 5，您可以选择以下两个Playground代码示例之一，以便UILabel使用一些交叉溶解动画为您的文本更改设置动画。

＃1。使用UIView的transition(with:duration:options:animations:completion:)class方法

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    let label = UILabel()

    override func viewDidLoad() {
        super.viewDidLoad()

        label.text = "Car"

        view.backgroundColor = .white
        view.addSubview(label)

        label.translatesAutoresizingMaskIntoConstraints = false
        label.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(toggle(_:)))
        view.addGestureRecognizer(tapGesture)
    }

    @objc func toggle(_ sender: UITapGestureRecognizer) {
        let animation = {
            self.label.text = self.label.text == "Car" ? "Plane" : "Car"
        }
        UIView.transition(with: label, duration: 2, options: .transitionCrossDissolve, animations: animation, completion: nil)
    }

}

let controller = ViewController()
PlaygroundPage.current.liveView = controller

＃2。使用CATransition和CALayer的add(_:forKey:)方法

import UIKit
import PlaygroundSupport

class ViewController: UIViewController {

    let label = UILabel()
    let animation = CATransition()

    override func viewDidLoad() {
        super.viewDidLoad()

        label.text = "Car"

        animation.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
        // animation.type = CATransitionType.fade // default is fade
        animation.duration = 2

        view.backgroundColor = .white
        view.addSubview(label)

        label.translatesAutoresizingMaskIntoConstraints = false
        label.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        label.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(toggle(_:)))
        view.addGestureRecognizer(tapGesture)
    }

    @objc func toggle(_ sender: UITapGestureRecognizer) {
        label.layer.add(animation, forKey: nil) // The special key kCATransition is automatically used for transition animations
        label.text = label.text == "Car" ? "Plane" : "Car"
    }

}

let controller = ViewController()
PlaygroundPage.current.liveView = controller

Swift 4.2解决方案（采用4.0答案并更新以供新枚举编译）

extension UIView {
    func fadeTransition(_ duration:CFTimeInterval) {
        let animation = CATransition()
        animation.timingFunction = CAMediaTimingFunction(name:
            CAMediaTimingFunctionName.easeInEaseOut)
        animation.type = CATransitionType.fade
        animation.duration = duration
        layer.add(animation, forKey: CATransitionType.fade.rawValue)
    }
}

func updateLabel() {
myLabel.fadeTransition(0.4)
myLabel.text = "Hello World"
}

系统默认值的0.25 duration和.curveEaseInEaseOut的timingFunction通常是最好的，以确保动画之间的一致性，可以将其省略：

let animation = CATransition()
label.layer.add(animation, forKey: nil)
label.text = "New text"

这与编写此代码相同：

let animation = CATransition()
animation.duration = 0.25
animation.timingFunction = .curveEaseInEaseOut
label.layer.add(animation, forKey: nil)
label.text = "New text"

这是基于@SwiftArchitect的代码的C＃UIView扩展方法。当涉及自动布局并且控件需要根据标签的文本移动时，此调用代码将标签的Superview用作过渡视图，而不是标签本身。我为该操作添加了一个lambda表达式，以使其更加封装。

public static void FadeTransition( this UIView AView, double ADuration, Action AAction )
{
  CATransition transition = new CATransition();

  transition.Duration = ADuration;
  transition.TimingFunction = CAMediaTimingFunction.FromName( CAMediaTimingFunction.Linear );
  transition.Type = CATransition.TransitionFade;

  AView.Layer.AddAnimation( transition, transition.Type );
  AAction();
}

调用代码：

  labelSuperview.FadeTransition( 0.5d, () =>
  {
    if ( condition )
      label.Text = "Value 1";
    else
      label.Text = "Value 2";
  } );

如果您想Swift延迟执行此操作，请尝试以下操作：

delay(1.0) {
        UIView.transitionWithView(self.introLabel, duration: 0.25, options: [.TransitionCrossDissolve], animations: {
            self.yourLabel.text = "2"
            }, completion:  { finished in

                self.delay(1.0) {
                    UIView.transitionWithView(self.introLabel, duration: 0.25, options: [.TransitionCrossDissolve], animations: {
                        self.yourLabel.text = "1"
                        }, completion:  { finished in

                    })
                }

        })
    }

使用@马特创建了以下功能- https://stackoverflow.com/a/24318861/1982051：

func delay(delay:Double, closure:()->()) {
    dispatch_after(
        dispatch_time(
            DISPATCH_TIME_NOW,
            Int64(delay * Double(NSEC_PER_SEC))
        ),
        dispatch_get_main_queue(), closure)
}

在Swift 3中会变成这个

func delay(_ delay:Double, closure:()->()) {
    let when = DispatchTime.now() + delay
    DispatchQueue.main.after(when: when, execute: closure)
}

还有另一种解决方案来实现这一目标。此处已描述。这个想法是通过以下方式子类化UILabel和覆盖action(for:forKey:)函数：

class LabelWithAnimatedText: UILabel {
    override var text: String? {
        didSet {
            self.layer.setValue(self.text, forKey: "text")
        }
    }

    override func action(for layer: CALayer, forKey event: String) -> CAAction? {
        if event == "text" {
            if let action = self.action(for: layer, forKey: "backgroundColor") as? CAAnimation {
                let transition = CATransition()
                transition.type = kCATransitionFade

                //CAMediatiming attributes
                transition.beginTime = action.beginTime
                transition.duration = action.duration
                transition.speed = action.speed
                transition.timeOffset = action.timeOffset
                transition.repeatCount = action.repeatCount
                transition.repeatDuration = action.repeatDuration
                transition.autoreverses = action.autoreverses
                transition.fillMode = action.fillMode

                //CAAnimation attributes
                transition.timingFunction = action.timingFunction
                transition.delegate = action.delegate

                return transition
            }
        }
        return super.action(for: layer, forKey: event)
    }
}

用法示例：

// do not forget to set the "Custom Class" IB-property to "LabelWithAnimatedText"
// @IBOutlet weak var myLabel: LabelWithAnimatedText!
// ...

UIView.animate(withDuration: 0.5) {
    myLabel.text = "I am animated!"
}

myLabel.text = "I am not animated!"