ios - swift:在 ViewController 返回后显示动画

Question

我有第一个ViewController和第二个ViewController。当我从第二个 ViewController 返回到第一个 ViewController 时，我想在第一个 ViewController 中显示按钮。

要返回，我使用以下代码:

self.dismiss(animated: true, completion: nil)

此代码用于在第一个 ViewController 中显示按钮

@IBOutlet weak var infoButton: UIButton!
@IBOutlet weak var nextButton: UIButton!

@IBOutlet weak var infoButtonTopConstraint: NSLayoutConstraint!
@IBOutlet weak var nextButtonBottomConstraint: NSLayoutConstraint!
@IBOutlet weak var infoButtonHeightConstraint: NSLayoutConstraint!
@IBOutlet weak var nextButtonHeightConstraint: NSLayoutConstraint!

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)

    showButtonAnimation()
    //animaton()
}

func showButtonAnimation() {

    self.infoButtonTopConstraint.constant += self.infoButtonHeightConstraint.constant
    self.nextButtonBottomConstraint.constant -= self.nextButtonHeightConstraint.constant

    UIView.animate(withDuration: 1.0, delay: 0.0,
                   options: [], animations: {
                    self.view.layoutIfNeeded()

    })
}

但是当我从第二个 ViewController 返回时，按钮没有显示。

Answer 1

替换这个

func showButtonAnimation() {
    self.view.layoutIfNeeded()
    UIView.animate(withDuration: 1.0, delay: 0.0,
                       options: [], animations: {
        self.infoButtonTopConstraint.constant += self.infoButtonHeightConstraint.constant
        self.nextButtonBottomConstraint.constant -= self.nextButtonHeightConstraint.constant
        self.view.layoutIfNeeded()

    })
}

编辑 1

viewWillAppear 未调用原因:您将第二个 viewController 呈现为 overCurrentContext modalPresentationStyle。

只需将 overCurrentContext 替换为 fullScreen 即可。