当视图框架为零时无法同时满足约束

Question

我创建视图

init(){
   super.init(frame: .zero)
}

创建视图后我想设置我的子视图

func setViews(){
    self.addSubview(labelView)
    self.addConstraintsWithFormat("V:|-10-[v0]-10-|", views: labelView)
    self.addConstraintsWithFormat("H:|-10-[v0]-10-|", views: labelView)
}

一切正常，但我有警告

Probably at least one of the constraints in the following list is one you
don't want. Try this: (1) look at each constraint and try to figure out
which you don't expect; (2) find the code that added the unwanted
constraint or constraints and fix it. (Note: If you're seeing
NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the 
documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 


 (
        "<NSLayoutConstraint:0x7f87ea8e6520 V:|-(10)-[BIPartners.labelView:0x7f87eb56be20]   (Names: '|':BIPartners.labelView:0x7f87eb56a320 )>",
        "<NSLayoutConstraint:0x7f87ea8e6af0 V:[BIPartners.labelView:0x7f87eb56be20]-(10)-|   (Names: '|':BIPartners.labelView:0x7f87eb56a320 )>",
        "<NSLayoutConstraint:0x7f87e868bdc0 '_UITemporaryLayoutHeight' V:[BIPartners.labelView:0x7f87eb56a320(0)]>"
    )

我知道问题出在我将帧设置为零时。我将框架设置为零，并将垂直边距设置为 10。我应该如何解决这个问题？

Answer 1

使用 WTF Auto Layout 了解您的错误。

在设置约束之前检查视图的 bounds。如果等于 CGRect.zero，则不应用约束。

Answer 2

您应该通过将标签底部固定约束的优先级降低到小于 1000 来解决此问题：

self.addConstraintsWithFormat("V:|-10-[v0]-10(@750)-|", views: labelView)

这将消除您的约束的歧义，保留您的底部填充和标签的固有高度。

基本上，当您想要使用固有内容大小时并将标签固定在两侧时，就会出现这种歧义。

当然，还有其他方法可以获得所需的间距（边距），但这个答案最接近你想要做的。

当视图框架为零时无法同时满足约束

Unable to simultaneously satisfy constraints when view frame is zero

nslayoutconstraint

swift