如何在Xcode playground中使用自动布局约束显示视图? [英] How can I display views using autolayout constraints in Xcode playground?
问题描述
我正在尝试在XCode playground 中显示使用自动布局约束配置的视图,但它似乎不起作用。这就像游乐场完全忽略了约束,我无法在任何地方找到有关此问题的信息。
I am trying to display views configured with autolayout constraints in XCode playground, but it doesn't seem to work. It's like playground ignores the constraints completely, and I can't find information about this issue anywhere.
这是我尝试过的代码:
let view = UIView()
view.frame = CGRectMake(0, 0, 400, 200)
view.backgroundColor = UIColor.lightGrayColor()
let label = UILabel() // I can only see the label if I set a frame
// UILabel(frame: CGRectMake(0, 0, 200, 50))
label.backgroundColor = UIColor.greenColor()
label.text = "I am a label"
label.setTranslatesAutoresizingMaskIntoConstraints(false)
view.addSubview(label)
let views = ["label":label]
let options = NSLayoutFormatOptions(0)
let cs1 = NSLayoutConstraint.constraintsWithVisualFormat(
"H:|-[label]-|", options: options, metrics: nil, views:views )
let cs2 = NSLayoutConstraint.constraintsWithVisualFormat(
"V:|-[label]-|", options: options, metrics: nil, views:views )
view.addConstraints(cs1)
view.addConstraints(cs2)
提前致谢
推荐答案
据说你可以使用的
预览你的用户界面。 liveView
属性PlaygroundPage
That being said you can use the liveView
property of PlaygroundPage
to preview your UI.
import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = myLiveView
这是一个链接进一步扩展。
如果它不起作用你可能需要触发 layoutIfNeeded
但是这不应该真正解决问题,因为Swift 4
If its not working you may need to trigger a layoutIfNeeded
but that shouldn't really solve the issue since Swift 4
此外,在您的视图中包含 translatesAutoresizingMaskIntoConstraints = false
。像:
Also, include translatesAutoresizingMaskIntoConstraints = false
on your view. Like:
import PlaygroundSupport
myLiveView.translatesAutoresizingMaskIntoConstraints = false
PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = myLiveView
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