如何使標簽在swift中淡入或淡出

Question

我希望在viewDidLoad()中使標簽淡入，然后在計時器淡出3之后。 我不熟悉fadein或fadeout功能。

我該怎么做呢？

Answer 1

我的建議是利用Swift擴展來使代碼更加模塊化和易於使用。 例如，如果要在多個視圖上制作多個標簽fadein / out或一個標簽淡入/淡出，則必須在任何地方傳遞animateWithDuration方法，這可能很麻煩。 更清潔的替代方法是創建一個名為UIView.swift的文件（我們的UIView擴展名）。 將以下代碼添加到此文件：

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)
}

}

現在，您可以為UIView的任何子項添加淡入/淡出功能（例如，UILabel，UIImage等）。 在viewDidLoad（）函數內，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()
        })

現在，您可以將此示例代碼用於圖像視圖，標簽，文本視圖，滾動視圖或UIView的任何子項。 我希望這有幫助。

Answer 2

即使視圖已加載，當調用viewDidLoad時，用戶可能看不到它。 這意味着當您目擊它時，您可能會發現您的動畫似乎已經開始。 要解決此問題，您需要在viewDidAppear啟動動畫。

至於fadeIn和fadeOut函數 - 它們不存在。 你需要自己寫。 值得慶幸的是，這很容易做到這一點。 像下面這樣的東西可能已經足夠了。

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)
    }
}

Answer 3

為Swift 3更新了答案 - 使用擴展程序

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()
        })

Answer 4

更新Swift 3.1 - 關於@Andy代碼

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)
        }
    }

Answer 5

斯威夫特5

這對我很有用。 我將標簽放在“cardHeaderView”中。

@IBOutlet weak var cardHeaderView: UIView!

將其放在“viewDidAppear”中。 我的延遲為零，所以動畫會立即開始。

fadeViewInThenOut(view: cardHeaderView, delay: 0)

這是功能。

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)

}

Answer 6

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)
    }
}