我试图将40x40徽标放置在屏幕顶部，距顶部20pt，最后与父视图水平对齐。
var views = ["tableView":self.tableView!,"logoImageView":logoImageView,"view":self.view]
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:[logoImageView(40)]", options: nil, metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[logoImageView(40)]", options: nil, metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-20-[logoImageView]", options: nil, metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[view][logoImageView]", options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: views));
但这是我在调试器/控制台中遇到的错误。
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:0x7fa78487e8f0 V:|-(20)-[UIImageView:0x7fa784b29350] (Names: '|':UIView:0x7fa78373b8e0 )>",
"<NSLayoutConstraint:0x7fa784886f70 V:[UIView:0x7fa78373b8e0]-(0)-[UIImageView:0x7fa784b29350]>",
"<NSLayoutConstraint:0x7fa78488caa0 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7fa78373b8e0(667)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x7fa784886f70 V:[UIView:0x7fa78373b8e0]-(0)-[UIImageView:0x7fa784b29350]>
如果有人可以帮助解释问题所在和正确的解决方法，那将是很好的NSLayoutFormatOptions。
谢谢！
问题在于以下两个约束：
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-20-[logoImageView]", options: nil, metrics: nil, views: views))
self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:[view][logoImageView]", options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: views));
第一个说，的顶部logoImageView应该是其超级视图顶部起20分。第二个说的顶部logoImageView应该是的底部的0点view。
问题是，这view是的监督logoImageView。您可以知道，因为superview（|）在此约束中：
"<NSLayoutConstraint:0x7fa78487e8f0 V:|-(20)-[UIImageView:0x7fa784b29350] (Names: '|':UIView:0x7fa78373b8e0 )>",
在此约束条件下与相邻视图相同：
"<NSLayoutConstraint:0x7fa784886f70 V:[UIView:0x7fa78373b8e0]-(0)-[UIImageView:0x7fa784b29350]>",
因此，两个约束共同要求view高20点。但是，表格视图对该视图施加了667个高度，如以下约束所示：
"<NSLayoutConstraint:0x7fa78488caa0 'UIView-Encapsulated-Layout-Height' V:[UIView:0x7fa78373b8e0(667)]>"
因此，冲突。
我怀疑问题是您添加logoImageView了错误的视图，还是要在V:[view][logoImageView]视觉格式字符串中列出其他视图。
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我来说两句