如何解决NSLayoutConstraint错误？

Question

我的应用程序中有一个UITableView。它填充了一个名为Lesson Cell的Custom UITableCell。它看起来像http://i.imgur.com/VoCxkJa.png

每当此视图加载时它显示了一堆布局错误，如下所示。但我的Interface Builder看起来很好。我研究过＆amp;尝试了很多来解决这个错误。

请帮帮我。在此先感谢

2015-08-17 12:25:51.543 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:0x7f85706d4150 UILabel:0x7f85706eb5c0'How Old are You?'.leading == UITableViewCellContentView:0x7f85706ce730.leadingMargin + 8>",
    "<NSLayoutConstraint:0x7f85706c6450 UITableViewCellContentView:0x7f85706ce730.trailingMargin == UILabel:0x7f85706eb5c0'How Old are You?'.trailing + 50>",
    "<NSLayoutConstraint:0x7f85706e7710 'fittingSizeHTarget' H:[UITableViewCellContentView:0x7f85706ce730(34)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f85706c6450 UITableViewCellContentView:0x7f85706ce730.trailingMargin == UILabel:0x7f85706eb5c0'How Old are You?'.trailing + 50>

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.

修改

我在View Controller中使用Dynamic Table View Cell。可能是这个原因有什么问题吗？

   LessonTable.estimatedRowHeight = 120
   LessonTable.rowHeight = UITableViewAutomaticDimension

Answer 1

UILabel:0x7f85706eb5c0'How Old are You?'.trailing + 50>存在约束冲突，以便为您的案例轻松修复，只需为拥抱UILabel添加优先级。

来自代码：

[urLabelCell setContentHuggingPriority:UILayoutPriorityFittingSizeLevel forAxis:UILayoutConstraintAxisHorizontal];
[urLabelCell setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[urLabelCell setContentCompressionResistancePriority:UILayoutPriorityFittingSizeLevel forAxis:UILayoutConstraintAxisHorizontal];
[urLabelCell setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];

或在IB中：

并且基本上删除了这个规则之一：

"<NSLayoutConstraint:0x7f85706d4150 UILabel:0x7f85706eb5c0'How Old are You?'.leading == UITableViewCellContentView:0x7f85706ce730.leadingMargin + 8>",
    "<NSLayoutConstraint:0x7f85706c6450 UITableViewCellContentView:0x7f85706ce730.trailingMargin == UILabel:0x7f85706eb5c0'How Old are You?'.trailing + 50>",

或设置不同的优先级