Autolayout不工作和警告

我正在试图在视图底部的上方添加一个button。 我以编程方式添加自动布局约束，这里是我的代码。

- (void)viewDidLoad { [super viewDidLoad]; NSLog(@"height : %f", self.view.bounds.size.height); [self.view addConstraints: [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(>=topSpace)-[button1]" options:0 metrics:@{@"topSpace":@(self.view.bounds.size.height*0.9f)} views:@{@"button1" : self.button1}]]; // Do any additional setup after loading the view, typically from a nib. } 

该代码的结果显示在图像中 该button肯定不在superview的底部。 另外，当我运行我的程序时，我收到以下警告。

 2014-06-01 22:02:19.144 AutoLayout[2886:60b] 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) ( "<NSIBPrototypingLayoutConstraint:0x8d40590 'IB auto generated at build time for view with fixed frame' V:|-(269)-[UIButton:0x8d815c0] (Names: '|':UIView:0x8d82360 )>", "<NSLayoutConstraint:0x8c34f60 V:|-(>=432)-[UIButton:0x8d815c0] (Names: '|':UIView:0x8d82360 )>" ) Will attempt to recover by breaking constraint <NSLayoutConstraint:0x8c34f60 V:|-(>=432)-[UIButton:0x8d815c0] (Names: '|':UIView:0x8d82360 )> 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. 

对这两个问题的任何帮助。

Answer 1

一个“> =”约束本身不足以定位视图（系统如何知道多大？）。 改用“=”约束。 NSIBPrototypingLayoutConstraint是系统在IB中添加的约束，如果您不添加任何自己的话。 如果您要在IB中添加button，那么在那里添加约束也会更容易。 如果您想在代码中添加约束，那么在代码中创build并添加button（另一种方法是使用添加了IB的button，在添加自己的button之前删除所做的任何约束）。