为啥这些约束不起作用？

Posted 2023-03-12

【中文标题】为啥这些约束不起作用？

【英文标题】：Why aren't these constraints working?为什么这些约束不起作用？

【发布时间】：2013-06-24 14:21:04

【问题描述】：

我以编程方式在 UIView 内的三个视图上设置以下约束：

UIView *view1 = ((UIViewController *)[self.viewControllers objectAtIndex:0]).view;
UIView *view2 = ((UIViewController *)[self.viewControllers objectAtIndex:1]).view;
UIView *view3 = ((UIViewController *)[self.viewControllers objectAtIndex:2]).view;

NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(view1, view2, view3);
[self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[view1(==320)]-0-[view2(==320)]-0-[view3(==320)]|" options:0 metrics:0 views:viewsDictionary]];

我的意图是每个视图都是 320 像素宽，彼此齐平，没有间隙，并在包含 UIView 的左边缘上查看一个。

但是，在编译时，视图会一个接一个地排列，我会在控制台中看到以下内容：

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:0x211811c0 H:|-(0)-[UIView:0xc683790]   (Names: '|':UIView:0xc683320 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x21179820 h=-&- v=-&- UIView:0xc683790.midX == UIView:0xc683320.midX - 340>",
    "<NSLayoutConstraint:0x211793d0 H:[UIView:0xc6a50c0]-(0)-|   (Names: '|':UIView:0xc683320 )>",
    "<NSLayoutConstraint:0x21179390 H:[UIView:0xc6a50c0(320)]>",
    "<NSLayoutConstraint:0x21179350 H:[UIView:0xc6a05f0]-(0)-[UIView:0xc6a50c0]>",
    "<NSLayoutConstraint:0x211563d0 H:[UIView:0xc6a05f0(320)]>",
    "<NSLayoutConstraint:0x21156390 H:[UIView:0xc683790]-(0)-[UIView:0xc6a05f0]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x21179350 H:[UIView:0xc6a05f0]-(0)-[UIView:0xc6a50c0]>

【参考方案1】：

尝试设置

[view setTranslatesAutoresizingMaskIntoConstraints:NO];

对于您的所有观点，通常足以解决此类问题。