swift - 将 alpha 设置回 1.0 后，不会重新出现任何按钮/标签/任何内容

Question

我想要的:调用 Viewcontroller 后，我想淡入此 Viewcontroller 中的所有元素(背景除外)。背景必须保留。

出了什么问题:正如您在我的代码中看到的，要淡入某些内容，首先需要将其删除。删除部分做得很好。但是，当我想让它重新出现时，什么也没有发生。当我使用 print 函数查看随机标签的 alpha 值时，它被设置为 1.0。我不知道我做错了什么。

这是我的代码:

override func viewDidAppear(animated: Bool) {
    super.viewDidAppear(animated)
    Removeeverything()
    Fadein()
}

func Removeeverything() {
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UIButton {
            UIView.animateWithDuration(0.0, delay: 0.0, options: UIViewAnimationOptions.CurveEaseOut, animations: {

                btn.alpha = 0.0

                }, completion: nil)
        }
    }
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UILabel {
            UIView.animateWithDuration(0.0, delay: 0.0, options: UIViewAnimationOptions.CurveEaseOut, animations: {

                btn.alpha = 0.0

                }, completion: nil)
        }
    }
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UIImageView {
            UIView.animateWithDuration(0.0, delay: 0.0, options: UIViewAnimationOptions.CurveEaseOut, animations: {

                btn.alpha = 0.0

                }, completion: nil)
        }
    }
}

func Fadein() {
    Backgrond.alpha = 1.0
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UIButton {
            UIView.animateWithDuration(1.0, delay: 0.0, options: UIViewAnimationOptions.CurveEaseIn, animations: {

                btn.alpha = 1.0

                }, completion: nil)
        }
    }
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UILabel {
            UIView.animateWithDuration(1.0, delay: 0.0, options: UIViewAnimationOptions.CurveEaseIn, animations: {

                btn.alpha = 1.0

                }, completion: nil)
        }
    }
    for view in self.view.subviews as [UIView] {
        if let btn = view as? UIImageView {
            UIView.animateWithDuration(0.7, delay: 0.0, options: UIViewAnimationOptions.CurveEaseIn, animations: {

                btn.alpha = 1.0

                }, completion: nil)
        }
    }

}

Answer 1

我想说问题是 UIView.animateWithDuration 是异步执行的(也就是说 - 你的 fadeIn() 函数将在 中的动画之前执行removeEverything() 已完成)。

只需从 Removeeverything() 中删除 UIView.animateWithDuration 操作即可。由于您已将持续时间参数设置为 0.0，因此不会真正改变任何内容(除了代码现在应该可以工作)

func removeEverything() {
    for v in view.subviews.filter({ $0 is UIButton || $0 is UILabel || $0 is UIImageView }) {
        v.alpha = 0
    }
}

func fadeIn() {
    // Background.alpha = 1.0
    UIView.animateWithDuration(1.0, delay: 0, options: .CurveEaseIn, animations: {
        for v in view.subviews.filter({ $0 is UIButton || $0 is UILabel }) {
            v.alpha = 1
        }
    }, completion: nil)
    UIView.animateWithDuration(0.7, delay: 0, options: .CurveEaseIn, animations: {
        for v in view.subviews.filter({ $0 is UIImageView }) {
            v.alpha = 1
        }
    }, completion: nil)
}

该代码片段应该按预期工作。我在数组上使用了 filter 函数，并删除了一些不必要的转换，以使代码更具可读性。希望对您有帮助!