swift - "Fade in and out"动画不工作

Question

我有一段代码是我在 Xcode 的 View Controller 中编写的。在该代码之前，即使是名为 NEXTTIP 的按钮也能正常工作。但是现在加入动画后，动画不出来，按钮也不起作用。请帮忙!

    
    @IBAction func nextTip(sender: AnyObject) {
        func hideTip() {
            UIView.animateWithDuration(0.5,
                animations: {
                    self.titleLabel.alpha = 0
                    self.contentLabel.alpha = 0
                    self.imageView.alpha = 0
                },
                completion: { finished in
                    self.showTip
                }
            )
        }

        func showTip() {
            titleLabel.text = "For healthy teeth, don't brush after eating"
            contentLabel.text = "Don't brush your teeth immediately after meals and drinks, especially if they were acidic. Wait 30 to 60 minutes before brushing."
            imageView.image = UIImage(named:"teeth.jpg")
            UIView.animateWithDuration(0.5,
                                       animations: {
            })
        }
        
    }

Answer 1

您在 nextTip() 函数中所做的是定义两个新函数，hideTip() 和 showTip( )。你实际上并没有给他们打电话。在 Swift 的函数内部创建函数是一件完全合法的事情，但几乎可以肯定这不是你想在这里做的。您需要将 hideTip() 和 showTip() 的定义移到 nextTip(:) 函数之外，以便您的代码结构化像这样:

class MyViewController: UIViewController {
    func hideTip() {
        UIView.animateWithDuration(...)
        // etc.
    }

    func showTip() {
        // stuff
    }

    @IBAction func nextTip(sender: AnyObject) {
        hideTip()
    }
}