当排列的子视图的高度全为零时，UIStackView高度不为0

Question

我认为垂直UIStackView的高度应该是其排列视图的总高度。但是，当我将所有排列视图的帧高度更改为0时，即使调用view.layoutIfNeeded()，UIStackView的帧高度仍然具有非零值，并且所有排列的视图都消失了。我也尝试将UIStackView的Clip to Bounds设置为true，但它仍然无效。这是我的代码：

override func viewDidLoad() {
  super.viewDidLoad()
  print("Before --- UIStackView.frame.height: \(stackView.frame.height)")
  print("Before --- firstLabel.frame.height: \(firstLabel.frame.height)")
  print("Before --- secondLabel.frame.height: \(secondLabel.frame.height)")
  print("Before --- thirdLabel.frame.height: \(thirdLabel.frame.height)")
  print("Before --- forthLabel.frame.height: \(forthLabel.frame.height)")
  for view in stackView.arrangedSubviews {
    view.frame = CGRect(x: view.frame.origin.x, y: view.frame.origin.y, width: view.frame.width, height: 0)
  }
  print("===================================")
  print("After --- UIStackView.frame.height: \(stackView.frame.height)")
  print("After --- firstLabel.frame.height: \(firstLabel.frame.height)")
  print("After --- secondLabel.frame.height: \(secondLabel.frame.height)")
  print("After --- thirdLabel.frame.height: \(thirdLabel.frame.height)")
  print("After --- forthLabel.frame.height: \(forthLabel.frame.height)")
  view.layoutIfNeeded()
}

这是日志：

Before --- UIStackView.frame.height: 82.0
Before --- firstLabel.frame.height: 20.5
Before --- secondLabel.frame.height: 20.5
Before --- thirdLabel.frame.height: 20.5
Before --- forthLabel.frame.height: 20.5
 ===================================
After --- UIStackView.frame.height: 82.0
After --- firstLabel.frame.height: 0.0
After --- secondLabel.frame.height: 0.0
After --- thirdLabel.frame.height: 0.0
After --- forthLabel.frame.height: 0.0

Answer 1

我认为您手动使用自动布局和设置框架的混合。要看到一切都按预期工作，而不是设置标签＆＃39;高度为0的帧将其text属性设置为空字符串（导致高度为0的intrinsicContentSize）：

// Your print statements BEFORE...

for arrangedSubview in stackView.arrangedSubviews {
    if let label = arrangedSubview as? UILabel {
        label.text = ""
    }
}
view.layoutIfNeeded()

// Your print statements AFTER...

结果：

Answer 2

使用堆栈视图，您只需隐藏子视图即可调整其高度。

for view in stackView.arrangedSubviews {
    view.isHidden = true
}