当我将它们设置为特定大小时，使用NSLayoutConstraint获取错误

Question

我在每个4边都有4 UIButtons constraints，宽constraint。 （Xcode让我在其中3个上设置宽度constraint，但我做了4，只是为了使编码更简单。）

然后我将所有4个宽度constraints添加到NSArray。当我将宽度constraint设置为以下内容时：

[self.constraintArray[0] setConstant:cellWdith / 3];
[self.constraintArray[1] setConstant:cellWdith / 3];
[self.constraintArray[3] setConstant:cellWdith / 3];
[self.constraintArray[2] setConstant:0];

我没有收到任何错误。但是当我将constraints设置为此时：

[self.constraintArray[1] setConstant:cellWidth / 6];
[self.constraintArray[2] setConstant:cellWidth / 6];
[self.constraintArray[3] setConstant:cellWidth / 3];
[self.constraintArray[0] setConstant:cellWidth / 3];

Xcode给我一个错误，说它无法满足所有constraints。但在模拟器中，一切看起来都应该如此。

模拟器Xcode出错：

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:0x7fcd51552710 H:[UIButton:0x7fcd514f64b0'Income'(62)]>",
    "<NSLayoutConstraint:0x7fcd5155b630 H:[UIButton:0x7fcd5155b410'All'(125)]>",
    "<NSLayoutConstraint:0x7fcd5155daf0 H:[UIButton:0x7fcd5155d8b0'Expense'(0)]>",
    "<NSLayoutConstraint:0x7fcd5155de40 H:[UIButton:0x7fcd5156e5e0'Button'(125)]>",
    "<NSLayoutConstraint:0x7fcd5156eb30 H:|-(0)-[UIButton:0x7fcd5156e5e0'Button']   (Names: '|':UITableViewCellContentView:0x7fcd515525f0 )>",
    "<NSLayoutConstraint:0x7fcd5156ebd0 H:[UIButton:0x7fcd5156e5e0'Button']-(0)-[UIButton:0x7fcd514f64b0'Income']>",
    "<NSLayoutConstraint:0x7fcd5157f620 H:[UIButton:0x7fcd514f64b0'Income']-(0)-[UIButton:0x7fcd5155d8b0'Expense']>",
    "<NSLayoutConstraint:0x7fcd5157f710 H:[UIButton:0x7fcd5155b410'All']-(0)-|   (Names: '|':UITableViewCellContentView:0x7fcd515525f0 )>",
    "<NSLayoutConstraint:0x7fcd5157f7b0 H:[UIButton:0x7fcd5155d8b0'Expense']-(0)-[UIButton:0x7fcd5155b410'All']>",
    "<NSLayoutConstraint:0x7fcd515bb460 'UIView-Encapsulated-Layout-Width' H:[UITableViewCellContentView:0x7fcd515525f0(375)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fcd5155de40 H:[UIButton:0x7fcd5156e5e0'Button'(125)]>

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.

我该怎么办才能收到错误？

更新

以下是constraints：

的图片

Answer 1

错误日志显示您有4个按钮，每个按钮都有固定大小。每个按钮被约束为在它们与它们最近的相邻按钮之间具有零间隙（或者在边缘上的那些按钮的表格视图单元的内容视图的边缘）。为了满足所有这些约束，单元格的宽度必须是按钮的约束宽度的总和。但只有在你的一个限制因素之后才会出现这种情况。常数已更改：125 + 0 + 62 + 125！= 375.

因为您正在以编程方式确保您的按钮＆＃39;组合宽度填充单元格的宽度，您可以删除将最终按钮的后缘与单元格的后缘相关联的约束。这样就不会出现约束冲突，即使只有一个约束被改变了。

此外，您的变量cellWidth似乎是一个整数而不是CGFloat，因此您正在进行整数除法，它总是返回一个整数。 375/6 = 62，但375.0 / 6.0 = 62.5。

Answer 2

尝试此操作：选择所有按钮并清除约束，并将其重置为两者的建议约束（任意宽度 - 任何高度和常规宽度 - 常规高度尺寸类）。它对我有用。