StackView isHidden 属性未按预期更新

StackView isHidden attribute not updating as expected

我正在尝试更新 UIStackView,以便在 UITextField 的值等于 "Other" 时显示一个字段。这是我的代码:

@IBOutlet var stackView: UIStackView!
func updateView() {
    print("UPDATING")
    UIView.animate(withDuration: 0.25, animations: { () -> Void in
         if(self.myTextField.text! == "Other") {
              print("SHOWING")
              self.stackView.arrangedSubviews[3].isHidden = false
         } else {
              print("HIDING")
              self.stackView.arrangedSubviews[3].isHidden = true
         }
         print("Is hidden: \(self.stackView.arrangedSubviews[3].isHidden )")
    })

示例输出如下所示:

> UPDATING
> HIDING
> Is hidden: true
> UPDATING
> SHOWING
> Is hidden: true

如您所见,isHidden 属性报告为 true,无论上面的代码将其设置为什么。我真的不明白为什么会这样,但也许这里有人可以?有什么明显的东西要检查吗? isHidden 无法更新的原因是什么? (注意输出中没有出现错误)。

用户界面的更新总是必须在主线程上完成(定律)。

所以给你包起来 UI 更新主线:

@IBOutlet var stackView: UIStackView!
func updateView() {
    print("UPDATING")
    UIView.animate(withDuration: 0.25, animations: { () -> Void in
        DispatchQueue.main.async {  // UI updates on the main thread
            if(self.myTextField.text! == "Other") {
                print("SHOWING")
                self.stackView.arrangedSubviews[3].isHidden = false
             } else {
                print("HIDING")
                self.stackView.arrangedSubviews[3].isHidden = true
             }
             print("Is hidden: \(self.stackView.arrangedSubviews[3].isHidden )")
        }
    })

尝试与 isHidden 一起操纵 alpha 属性:

self.stackView.arrangedSubviews[3].isHidden = true
self.stackView.arrangedSubviews[3].alpha = 0

self.stackView.arrangedSubviews[3].isHidden = false
self.stackView.arrangedSubviews[3].alpha = 1

这是已知 UIStackView 错误 (http://www.openradar.me/25087688). There is a thread on SO about it: ()。长话短说:

The bug is that hiding and showing views in a stack view is cumulative. Weird Apple bug. If you hide a view in a stack view twice, you need to show it twice to get it back.

要解决此问题,您可以使用以下扩展:

extension UIView {
    var isHiddenInStackView: Bool {
        get {
            return isHidden
        }
        set {
            if isHidden != newValue {
                isHidden = newValue
            }
        }
    }
}