问题描述

我在 UITableViewCell 中有两个彼此相邻的 UILabel 视图.左边的有一条线，右边的可以有多条线，并使用剩下的任何水平空间.两个标签与单元格顶部的距离相同.单元格的高度由右标签的高度决定.在某些情况下，我会在右侧 UILabel 上方和下方看到不需要的额外空间，因此它们不是顶部对齐的.进一步研究，我发现 hasAmbiguousLayout 为两个标签返回 YES.

I have two UILabel views next to each other in an UITableViewCell. The left one has one line, the right one can have multiple lines and uses whatever horizontal space that is left. Both labels have the same distance from the top of the cell. The height of the cell is dictated by the height of the right label. In some cases, I see unwanted additional space above and under the right UILabel, and therefore they are not top-aligned. Looking into it more, I found that hasAmbiguousLayout returns YES for both labels.

当我在调试器中调用 constraintsAffectingLayoutForAxis 时，我得到以下输出:

When I call constraintsAffectingLayoutForAxis in the debugger, I get the following output:

(lldb) po [0x7b769520 constraintsAffectingLayoutForAxis:0]
<__NSArrayM 0x7b6cb340>(
<NSAutoresizingMaskLayoutConstraint:0x7b76abf0 h=--& v=--& 'UIView-Encapsulated-Layout-Left' H:|-(0)-[UITableViewCellContentView:0x7b768fc0]   (Names: '|':MyTVCell:0x7b769330'MyTVCell' )>,
<NSLayoutConstraint:0x7b76b010 H:|-(15)-[UILabel:0x7b769520'Number']   (Names: '|':UITableViewCellContentView:0x7b768fc0 )>,
<NSContentSizeLayoutConstraint:0x7b769a90 H:[UILabel:0x7b769520'Number'(131)] Hug:250 CompressionResistance:750>
)

对于位于第一个 UILabel 右侧的第二个 UILabel，我得到这个:

For a second UILabel that is positioned to the right of the first UILabel, I get this:

(lldb) po [0x7b769710 constraintsAffectingLayoutForAxis:0]
<__NSArrayM 0x7b6cb9e0>(
<NSContentSizeLayoutConstraint:0x7b769a90 H:[UILabel:0x7b769520'Number'(131)] Hug:250 CompressionResistance:750>,
<NSAutoresizingMaskLayoutConstraint:0x7b76abf0 h=--& v=--& 'UIView-Encapsulated-Layout-Left' H:|-(0)-[UITableViewCellContentView:0x7b768fc0]   (Names: '|':MyTVCell:0x7b769330'MyTVCell' )>,
<NSLayoutConstraint:0x7b76b010 H:|-(15)-[UILabel:0x7b769520'Number']   (Names: '|':UITableViewCellContentView:0x7b768fc0 )>,
<NSLayoutConstraint:0x7b76b230 H:[UILabel:0x7b769520'Number']-(15)-[UILabel:0x7b769710'Q12472']>,
<NSLayoutConstraint:0x7b76ab90 'UIView-Encapsulated-Layout-Width' H:[UITableViewCellContentView:0x7b768fc0(320)]>,
<NSLayoutConstraint:0x7b76b310 UILabel:0x7b769710'Q12472'.trailing == UITableViewCellContentView:0x7b768fc0.trailing - 15>
)

谁能根据上面的输出解释为什么这些标签的布局不明确?

Could anyone explain based on the output above why these labels have an ambiguous layout?

更新: NSAutoresizingMaskLayoutConstraint 约束属于单元格的 contentView.两个标签都将 translatesAutoresizingMaskIntoConstraints 设置为 NO.

Update: The NSAutoresizingMaskLayoutConstraint constraint belongs to the contentView of the cell. Both labels have set translatesAutoresizingMaskIntoConstraints to NO.

更新 2: 以下是我对 contentView 和两个标签的限制:

Update 2: Here are the constraints I have for the contentView and the two labels:

2015-02-26 07:35:25.559 contentView constraints: (
    "<NSLayoutConstraint:0x7be541e0 V:|-(8)-[UILabel:0x7be537d0]   (Names: '|':UITableViewCellContentView:0x7be535a0 )>",
    "<NSLayoutConstraint:0x7be54240 H:|-(15)-[UILabel:0x7be537d0]   (Names: '|':UITableViewCellContentView:0x7be535a0 )>",
    "<NSLayoutConstraint:0x7be54310 V:|-(8)-[UILabel:0x7be53990]   (Names: '|':UITableViewCellContentView:0x7be535a0 )>",
    "<NSLayoutConstraint:0x7be54340 H:[UILabel:0x7be537d0]-(15)-[UILabel:0x7be53990]>",
    "<NSLayoutConstraint:0x7be54370 UILabel:0x7be53990.trailing == UITableViewCellContentView:0x7be535a0.trailing - 15>",
    "<NSLayoutConstraint:0x7be543c0 UILabel:0x7be53990.bottom == UITableViewCellContentView:0x7be535a0.bottom - 8>",
    "<NSContentSizeLayoutConstraint:0x7be53cd0 H:[UILabel:0x7be537d0(109)] Hug:250 CompressionResistance:750>",
    "<NSContentSizeLayoutConstraint:0x7be53d10 V:[UILabel:0x7be537d0(21)] Hug:250 CompressionResistance:750>",
    "<NSContentSizeLayoutConstraint:0x7be53eb0 H:[UILabel:0x7be53990(20)] Hug:250 CompressionResistance:750>",
    "<NSContentSizeLayoutConstraint:0x7be53f10 V:[UILabel:0x7be53990(20)] Hug:250 CompressionResistance:750>"
)
2015-02-26 07:35:25.560 left label constraints: (
    "<NSContentSizeLayoutConstraint:0x7be53cd0 H:[UILabel:0x7be537d0(109)] Hug:250 CompressionResistance:750>",
    "<NSContentSizeLayoutConstraint:0x7be53d10 V:[UILabel:0x7be537d0(21)] Hug:250 CompressionResistance:750>"
)
2015-02-26 07:35:25.561 right label constraints:(
    "<NSContentSizeLayoutConstraint:0x7be53eb0 H:[UILabel:0x7be53990(20)] Hug:250 CompressionResistance:750>",
    "<NSContentSizeLayoutConstraint:0x7be53f10 V:[UILabel:0x7be53990(20)] Hug:250 CompressionResistance:750>"
)

这是一张图片，显示了我的限制以及出了什么问题:

Here is a picture showing the constraints I have and what goes wrong:

推荐答案

我通过为正确的 UILabel 添加解决了它:

I solved it by adding for the right UILabel:

[self.bodyLabel setContentHuggingPriority: UILayoutPriorityFittingSizeLevel forAxis: UILayoutConstraintAxisHorizontal];

另一件事是我在 updateConstraints 中测试歧义，而我应该在 layoutSubviews

The other thing is that I was testing for ambiguity in updateConstraints, while I should have done it at the end of layoutSubviews

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