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以编程方式使用布局定位创建子视图

layout-anchor constraints swift ios

6

halapgos1 · 技术社区 · 8 年前

我创建了一个 UIView 以编程方式使用 layout anchors . 现在我想添加一个 UILabel 在此视图内。以下是我目前的代码:

let centerView = UIView()
centerView.translatesAutoresizingMaskIntoConstraints = false
centerView.backgroundColor = UIColor.white
view.addSubview(centerView)
centerView.leftAnchor.constraint(equalTo: view.leftAnchor, constraint: 20).isActive = true
centerView.rightAnchor.constraint(equalTo: view.rightAnchor, constraint: -20).isActive = true

let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "Testing" 
label.textColor = UIColor.black
centerView.addSubview(label)
label.leftAnchor.constraint(equalTo: centerView.leftAnchor).isActive = true

我以为这个标签会显示在参考 centerView 但它是参照 UIWindow . 这是当前视图层次结构:

UIWindow --> UIView (centerView) --> UILabel (label)

我需要在里面添加多个标签 centerView中心视图 根据我的理解,这条链会变长,而我希望几个标签都在下面 centerView中心视图

         UIWindow

            |

     UIView (centerView)

     /      |      \
  Label 1  Label 2  Label 3

如何实现这种层次结构?

1 回复 | 直到 8 年前

1

10

vacawama 8 年前

您做得很正确,只是没有提供足够的约束。我在Swift游乐场中尝试了您的代码,并添加了一些额外的约束,这表明标签是相对于 centerView 正如预期的那样:

let view = UIView(frame: CGRect(x: 0, y: 0, width: 300, height: 500))

let centerView = UIView()
centerView.translatesAutoresizingMaskIntoConstraints = false
centerView.backgroundColor = UIColor.white
view.addSubview(centerView)
centerView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 20).isActive = true
centerView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -20).isActive = true
centerView.topAnchor.constraint(equalTo: view.topAnchor, constant: 20).isActive = true
centerView.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -20).isActive = true

let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "Testing"
label.textColor = UIColor.black
label.backgroundColor = UIColor.yellow
centerView.addSubview(label)
label.leftAnchor.constraint(equalTo: centerView.leftAnchor).isActive = true
label.topAnchor.constraint(equalTo: centerView.topAnchor).isActive = true

view.layoutIfNeeded()

下面是在操场上跑步: