ios - 约束 objective-c

Question

什么意思

无法同时满足约束条件。可能至少以下列表中的约束条件之一是您不想要的。

试试这个: (1)查看每个约束并尝试找出您不期望的； (2) 找到添加了不需要的约束或约束的代码并修复它。

(
           "<NSLayoutConstraint:0x7f871d1303b0 H:               [UIButton:0x7f871d197640(30)]>",   
"<NSLayoutConstraint:0x7f871d1a1c40 H:[UIButton:0x7f871d196960'LB'(30)]>",
"<NSLayoutConstraint:0x7f871d1a4570 H:[UIView:0x7f871d196d60]-(100.8)-|   (Names: '|':UIView:0x7f871ac66870 )>",
"<NSLayoutConstraint:0x7f871d1a5200 H:|-(0)-[UIView:0x7f871d196d60]   (Names: '|':UIView:0x7f871ac66870 )>",
"<NSLayoutConstraint:0x7f871d19c5f0 H:[UIView:0x7f871ac66870]-(0)-|   (Names: '|':UIView:0x7f871d199d70 )>",
"<NSLayoutConstraint:0x7f871d19c640 H:|-(20)-[UIView:0x7f871ac66870]   (Names: '|':UIView:0x7f871d199d70 )>",
"<NSLayoutConstraint:0x7f871d1a8ca0 H:|-(0)-[UIView:0x7f871d199d70]   (Names: '|':UIView:0x7f871d199c00 )>",
"<NSLayoutConstraint:0x7f871d1a8d40 UIView:0x7f871d19c820.width == UIView:0x7f871d199d70.width>",
"<NSLayoutConstraint:0x7f871d1a8de0 H:[UIView:0x7f871d199d70]-(10)-[UIView:0x7f871d19c820]>",
"<NSLayoutConstraint:0x7f871d1a8e80 H:[UIView:0x7f871d19c820]-(10)-[UIView:0x7f871d1a7000]>",
"<NSLayoutConstraint:0x7f871d1a8f20 UIView:0x7f871d1a7000.width == UIView:0x7f871d199d70.width>",
"<NSLayoutConstraint:0x7f871d1a8f70 H:[UIView:0x7f871d1a7000]-(0)-|   (Names: '|':UIView:0x7f871d199c00 )>",
"<NSLayoutConstraint:0x7f871d1a9450 H:|-(15)-[UIButton:0x7f871d197640]   (Names: '|':UIView:0x7f871d19b130 )>",
"<NSLayoutConstraint:0x7f871d1a9540 H:[UIButton:0x7f871d197640]-(10)-[UIView:0x7f871d199c00]>",
"<NSLayoutConstraint:0x7f871d1a95e0 H:[UIView:0x7f871d199c00]-(10)-[UIButton:0x7f871d196960'LB']>",
"<NSLayoutConstraint:0x7f871d1a96d0 H:[UIButton:0x7f871d196960'LB']-(10)-|   (Names: '|':UIView:0x7f871d19b130 )>",
"<NSLayoutConstraint:0x7f871d1aa340 H:[UIView:0x7f871d19b130]-(0)-|   (Names: '|':UIView:0x7f871d19afc0 )>",
"<NSLayoutConstraint:0x7f871d1aa390 H:|-(0)-[UIView:0x7f871d19b130]   (Names: '|':UIView:0x7f871d19afc0 )>",
"<NSLayoutConstraint:0x7f871d1b7230 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7f871d19afc0(320)]>"
)

Will attempt to recover by breaking constraint 

 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.

Answer 1

这意味着您提供了比要求更多的约束，因此会产生歧义。

例如，如果您有一个高度为 30 的标签。

现在您给出约束，例如 top、leading 和 trailing with constant of 20 和 fixed height of 30。这意味着您的标签始终从顶部、左侧和右侧保持每边 20 的空间，并且始终保持 30 的高度。

没关系。

现在，如果您添加另一个约束，例如 fixed width with constant 50，这意味着标签的宽度应为 50。

现在，如果您的应用在 4 英寸设备上运行，那么您的屏幕宽度为 320。

因此，如果标签保持 50 的宽度，则无法保持 20 的左右间距，如果保持 20 的间距，则无法保持宽度。

这种情况称为歧义。

这是一个理解的例子。

您的约束在某处造成了这种歧义，因此请检查两次并删除不必要的或额外的约束。

希望这会有所帮助:)