iOS7上的自动布局崩溃，在iOS8上运行良好

Question

我正在使用针对＆gt; iOS7的Xcode 6.1（Beta）构建应用。 我有一个原型单元格，在故事板中完成了所有约束。它在iOS8（iPhone 6模拟器）上运行良好，当我在iOS7（iPhone 5S模拟器）上运行时，它崩溃并出现以下错误：

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) 
(
"<NSLayoutConstraint:0x7f901848bf00 UILabel:0x7f90190cb410.trailing == UILabel:0x7f90190c8110.trailing>",
"<NSLayoutConstraint:0x7f901848bf50 H:[UILabel:0x7f90190cb410]-(19)-|   (Names: '|':UITableViewCellContentView:0x7f9019076440 )>",
"<NSLayoutConstraint:0x7f901848bfa0 UILabel:0x7f90190cb410.leading == UILabel:0x7f90190c8110.leading>",
"<NSLayoutConstraint:0x7f9018490900 H:|-(15)-[UILabel:0x7f90190cb410]   (Names: '|':UITableViewCellContentView:0x7f9019076440 )>",
"<NSAutoresizingMaskLayoutConstraint:0x7f90184a7800 h=--& v=--& H:[UITableViewCellContentView:0x7f9019076440(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7f901848bf00 UILabel:0x7f90190cb410.trailing == UILabel:0x7f90190c8110.trailing>

Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

这是我的故事板相关内容：

我已经为约束尝试了许多不同的方法，每次我告诉标签它开始时（前导约束）和它结束的位置（尾随......）它们都会崩溃。而且我不想给出明确的高度......

有什么想法吗？

Answer 1

x位置有两组可能存在冲突的约束。尝试删除一对约束，这些约束将尾随和超级视图对齐，带有偏移量或尾随并导致字幕标签。

Answer 2

当您的单元格太小时，您的约束可能会发生碰撞。在界面构建器中，将单元格调整为非常小并查看它是否产生错误。如果是这样，您需要确保正确设置单元格大小