UIStackView“无法同时满足约束"在“压扁"上隐藏视图

问题描述

当我的 UIStackView 行"被压扁时，它们会抛出 AutoLayout 警告.但是，它们显示正常，除了这些日志记录之外没有其他问题:

When my UIStackView "rows" are squished, they throw AutoLayout warnings. However, they display fine and nothing else is wrong besides these sorts of loggings:

无法同时满足约束.以下列表中的至少一个约束可能是您不想要的.试试这个:(1)查看每个约束并尝试找出您不期望的；(2) 找到添加了一个或多个不需要的约束的代码并修复它.(注意:如果您看到不理解的 NSAutoresizingMaskLayoutConstraints，请参阅 UIView 属性 translatesAutoresizingMaskIntoConstraints 的文档)(

Unable to simultaneously satisfy constraints. 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) (

所以，我还不确定如何解决这个问题，但除了烦人之外，它似乎并没有破坏任何东西.

So, I'm not sure how to fix this yet, but it doesn't seem to break anything besides just being annoying.

有人知道怎么解决吗?有趣的是，布局约束经常被标记为 'UISV-hiding'，这表明它可能应该忽略子视图的最小高度或在这种情况下?

Does anyone know how to solve it? Interestingly, the layout constraints are tagged quite often with 'UISV-hiding', indicating that perhaps it should ignore the height minimums for subviews or something in this instance?

推荐答案

你遇到这个问题是因为当从 UIStackView 中设置子视图为隐藏时，它会首先将其高度限制为零，以便动画出来.

You get this issue because when setting a subview from within UIStackView to hidden, it will first constrain its height to zero in order to animate it out.

我收到以下错误:

2015-10-01 11:45:13.732 <redacted>[64455:6368084] Unable to simultaneously satisfy constraints.
    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:0x7f7f5be18c80 V:[UISegmentedControl:0x7f7f5bec4180]-(8)-|   (Names: '|':UIView:0x7f7f5be69d30 )>",
    "<NSLayoutConstraint:0x7f7f5be508d0 V:|-(8)-[UISegmentedControl:0x7f7f5bec4180]   (Names: '|':UIView:0x7f7f5be69d30 )>",
    "<NSLayoutConstraint:0x7f7f5bdfbda0 'UISV-hiding' V:[UIView:0x7f7f5be69d30(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f7f5be18c80 V:[UISegmentedControl:0x7f7f5bec4180]-(8)-|   (Names: '|':UIView:0x7f7f5be69d30 )>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

我试图做的是在我的 UIStackView 中放置一个 UIView，其中包含一个 UISegmentedControl 在每个边缘上插入 8 个点.

What I was trying to do, was to place a UIView within my UIStackView that contained a UISegmentedControl inset by 8pts on each edge.

当我将它设置为隐藏时，它会尝试将容器视图约束为零高度，但因为我有一组从上到下的约束，所以发生了冲突.

When I set it to hidden, it would try to constrain the container view to a zero height but because i have a set of constraints from top to bottom, there was a conflict.

为了解决这个问题，我将我的 8pt 上下约束优先级从 1000 更改为 999，以便 UISV-hiding 约束可以在需要时获得优先级.

To resolve the issue, I changed my 8pt top an bottom constraints priority from 1000 to 999 so the UISV-hiding constraint can then take priority if needed.

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