swift - 如何从容器 View 中为父 View Controller 中的约束更改设置动画？ ( swift 4)

Question

我在 View Controller 中有一个容器 View ，其中包含一个按钮，每次按下时都会在父 View Controller 中向下移动标签。我通过 prepare for segue 将标签的约束传递给容器。从那里我可以修改约束，但它不会动画。

我应该怎么做？

visual example

class ViewController: UIViewController {

    @IBOutlet weak var LabelTopConstraint: NSLayoutConstraint!

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "containerSegue" {
            let container = segue.destination as? Container
            container?.LabelTopConstraint = LabelTopConstraint
        }
    }
}

class Container: UIViewController {

    weak var LabelTopConstraint: NSLayoutConstraint!

    @IBAction func MoveLabelButtonPressed(_ sender: Any) {
        LabelTopConstraint.constant += 30
        UIView.animate(withDuration: 0.35, animations: {
            self.view.layoutIfNeeded()
        })
    }
}

Answer 1

100% 有效的答案你需要更新父 View 的布局，比如..

@IBAction func MoveLabelButtonPressed(_ sender: Any) {


    self.LabelTopConstraint.constant += 30 // Your constraint constant change


    UIView.animate(withDuration: 3.0) {
        self.parent?.view.layoutIfNeeded() // Force lays of all subviews on parent view .
    }

}

输出: