UIButton 不能在横向工作

Question

在我的 iOS 应用程序的一个 ViewController 中，有一个具有此功能的 UIButton：

@IBAction func openSettings(sender: AnyObject) {
    UIApplication.sharedApplication().openURL(NSURL(string: UIApplicationOpenSettingsURLString)!)
}

这可以正常工作，但是当从纵向更改为横向时，按钮不再起作用。我正在为此按钮使用自动布局。控制台这样说：

2016-06-05 17:15:31.238 MyApp[3975:1756888] 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. 
(
    "<_UILayoutSupportConstraint:0x15cf4a540 V:[_UILayoutGuide:0x15cf685a0(0)]>",
    "<_UILayoutSupportConstraint:0x15cd5c7d0 V:|-(0)-[_UILayoutGuide:0x15cf685a0]   (Names: '|':UIView:0x15e202490 )>",
    "<NSLayoutConstraint:0x15cf68f60 V:[_UILayoutGuide:0x15cf685a0]-(265)-[UIButton:0x15cf65310'Enable Push!']>",
    "<NSLayoutConstraint:0x15cf68fb0 UIButton:0x15cf65310'Enable Push!'.centerY == UIView:0x15e202490.centerY>",
    "<NSLayoutConstraint:0x15cf4b640 'UIView-Encapsulated-Layout-Height' V:[UIView:0x15e202490(414)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x15cf68f60 V:[_UILayoutGuide:0x15cf685a0]-(265)-[UIButton:0x15cf65310'Enable Push!']>

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.

有人知道或看到原因吗？

Answer 1

您有两个相互冲突的约束。第一个

V:[_UILayoutGuide:0x15cf685a0]-(265)-[UIButton:0x15cf65310'Enable Push!']

正在尝试将按钮放置在距顶部布局指南 265 点的位置。第二个：

UIButton:0x15cf65310'Enable Push!'.centerY == UIView:0x15e202490.centerY

正在尝试使按钮在视图中垂直居中。决定是否希望按钮位于距顶部 265 点或垂直居中并删除其他约束。

Answer 2

您收到此警告的原因是您没有正确设置此按钮的自动布局。您添加了一个不需要的额外约束。您可以删除顶部约束 (265)，因为您已经设置了按钮的高度并对齐到视图的垂直中心。