ios - "Unable to simultaneously satisfy constraints"隐藏 View 上的 UIStackView "squished"

Question

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，除了这些类型的日志之外没有其他错误:

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，但它似乎并没有破坏任何东西，除了很烦人之外。

有谁知道怎么解决吗？有趣的是，布局约束经常被标记为'UISV-hiding'，表明在这种情况下它可能应该忽略 subview 或其他东西的高度最小值？

Answer 1

您会遇到此问题，因为当从 UIStackView 中将 subview 设置为隐藏时，它会首先将其高度限制为零，以便将其动画化。

我遇到了以下错误:

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.

我想做的是在我的 UIStackView 中放置一个 UIView，其中包含一个 UISegmentedControl 在每条边上插入 8pts。

当我将其设置为隐藏时，它会尝试将容器 View 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。

为了解决这个问题，我将我的 8pt 顶部和底部约束优先级从 1000 更改为 999，以便 UISV-hiding 约束可以在需要时优先。