我希望在viewDidLoad()中制作一个标签淡入淡出，然后在定时器淡出3之后。我不熟悉fadein或fadeout函数。
我该怎么做呢？
即使视图已加载，当调用viewDidLoad时，用户可能看不到它。这意味着当您目击它时，您可能会发现您的动画似乎已经开始。要解决此问题，您需要在viewDidAppear中启动动画。
至于fadeIn和fadeOut函数 - 它们不存在。你需要自己写。值得庆幸的是，这很容易做到这一点。像下面这样的东西可能已经足够了。
func fadeViewInThenOut(view : UIView, delay: NSTimeInterval) {
let animationDuration = 0.25
// Fade in the view
UIView.animateWithDuration(animationDuration, animations: { () -> Void in
view.alpha = 1
}) { (Bool) -> Void in
// After the animation completes, fade out the view after a delay
UIView.animateWithDuration(animationDuration, delay: delay, options: .CurveEaseInOut, animations: { () -> Void in
view.alpha = 0
},
completion: nil)
}
}
我的建议是利用Swift扩展来使代码更加模块化和易于使用。例如，如果要在多个视图上制作多个标签fadein / out或一个标签淡入/淡出，则必须在任何地方传递animateWithDuration方法，这可能很麻烦。更清洁的替代方法是创建一个名为UIView.swift的文件（我们的UIView扩展名）。将以下代码添加到此文件：
import Foundation
extension UIView {
func fadeIn(duration: NSTimeInterval = 1.0, delay: NSTimeInterval = 0.0, completion: ((Bool) -> Void) = {(finished: Bool) -> Void in}) {
UIView.animateWithDuration(duration, delay: delay, options: UIViewAnimationOptions.CurveEaseIn, animations: {
self.alpha = 1.0
}, completion: completion) }
func fadeOut(duration: NSTimeInterval = 1.0, delay: NSTimeInterval = 3.0, completion: (Bool) -> Void = {(finished: Bool) -> Void in}) {
UIView.animateWithDuration(duration, delay: delay, options: UIViewAnimationOptions.CurveEaseIn, animations: {
self.alpha = 0.0
}, completion: completion)
}
}
现在，您可以为任何UIView的子项添加淡入/淡出功能（例如，UILabel，UIImage等）。在viewDidLoad（）函数内，您可以添加：
self.statusLabel.alpha = 0
self.statusLabel.text = "Sample Text Here"
self.myLabel.fadeIn(completion: {
(finished: Bool) -> Void in
self.myLabel.fadeOut()
})
现在，您可以将此示例代码用于图像视图，标签，文本视图，滚动视图或UIView的任何子项。我希望这有帮助。
为Swift 3更新了答案 - 使用扩展程序
extension UIView {
func fadeIn(duration: TimeInterval = 1.0, delay: TimeInterval = 0.0, completion: @escaping ((Bool) -> Void) = {(finished: Bool) -> Void in}) {
UIView.animate(withDuration: duration, delay: delay, options: UIViewAnimationOptions.curveEaseIn, animations: {
self.alpha = 1.0
}, completion: completion)
}
func fadeOut(duration: TimeInterval = 1.0, delay: TimeInterval = 3.0, completion: @escaping (Bool) -> Void = {(finished: Bool) -> Void in}) {
UIView.animate(withDuration: duration, delay: delay, options: UIViewAnimationOptions.curveEaseIn, animations: {
self.alpha = 0.0
}, completion: completion)
}
}
用法：
self.statusLabel.alpha = 0
self.statusLabel.text = "Sample Text Here"
self.myLabel.fadeIn(completion: {
(finished: Bool) -> Void in
self.myLabel.fadeOut()
})
更新Swift 3.1 - 关于@Andy代码
func fadeViewInThenOut(view : UIView, delay: TimeInterval) {
let animationDuration = 0.25
// Fade in the view
UIView.animate(withDuration: animationDuration, animations: { () -> Void in
view.alpha = 1
}) { (Bool) -> Void in
// After the animation completes, fade out the view after a delay
UIView.animate(withDuration: animationDuration, delay: delay, options: [.curveEaseOut], animations: { () -> Void in
view.alpha = 0
}, completion: nil)
}
}
斯威夫特5
这对我很有用。我将标签放在“cardHeaderView”中。
@IBOutlet weak var cardHeaderView: UIView!
将其放在“viewDidAppear”中。我的延迟为零，所以动画会立即开始。
fadeViewInThenOut(view: cardHeaderView, delay: 0)
这是功能。
func fadeViewInThenOut(view : UIView, delay: TimeInterval) {
let animationDuration = 1.5
UIView.animate(withDuration: animationDuration, delay: delay, options: [UIView.AnimationOptions.autoreverse, UIView.AnimationOptions.repeat], animations: {
view.alpha = 0
}, completion: nil)
}
SWIFT 4.2
extension UIView {
func fadeIn(duration: TimeInterval = 1.0, delay: TimeInterval = 0.0, completion: @escaping ((Bool) -> Void) = {(finished: Bool) -> Void in}) {
UIView.animate(withDuration: duration, delay: delay, options: .curveEaseIn, animations: {
self.alpha = 1.0
}, completion: completion)
}
func fadeOut(duration: TimeInterval = 1.0, delay: TimeInterval = 3.0, completion: @escaping (Bool) -> Void = {(finished: Bool) -> Void in}) {
UIView.animate(withDuration: duration, delay: delay, options: .curveEaseIn, animations: {
self.alpha = 0.0
}, completion: completion)
}
}