iOS "Unable to simultaneously satisfy constraints"

Question

我将使用以下符号来解释涉及的视图：

{V} – “superview”，即根控制器的主视图
{Q} – 屏幕中央的矩形，用作测验
{W} – {Q}上方的白色条

在 iPad-Air2 模拟器上运行时，我得到以下输出：

2016-11-03 08:09:07.700117 MyApp[16645:6976134] [LayoutConstraints] 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) 
(
    "<NSAutoresizingMaskLayoutConstraint:0x60000009d600 h=--& v=--& QuizButtons:0x7fcb8e521830.width == 717   (active)>",
    "<NSLayoutConstraint:0x608000281fe0 H:|-(0)-[ImgWhiteBar:0x7fcb8e525020]   (active, names: '|':ViewTestVC:0x7fcb8e639b30 )>",
    "<NSLayoutConstraint:0x6080002820d0 H:[ImgWhiteBar:0x7fcb8e525020]-(0)-|   (active, names: '|':ViewTestVC:0x7fcb8e639b30 )>",
    "<NSLayoutConstraint:0x608000282210 ImgWhiteBar:0x7fcb8e525020.width == 1.07143*QuizButtons:0x7fcb8e521830.width   (active)>",
    "<NSLayoutConstraint:0x60000009b9e0 'UIView-Encapsulated-Layout-Width' ViewTestVC:0x7fcb8e639b30.width == 768   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x6080002820d0 H:[ImgWhiteBar:0x7fcb8e525020]-(0)-|   (active, names: '|':ViewTestVC:0x7fcb8e639b30 )>

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.

我对记录约束的解释是：

{Q}：默认<h=--& v=--&>，宽度=717
水平：{V.lead} -0- {W}
水平：{W} -0- {V.trail}
{W.width} = 1.07 * {Q.width}
{V.width} = 768

或者更简单一些

{Q.width} 必须是 717
{W.width} 必须是 768.21531
{W} 必须触及 {V} 的两边
{V.width} = 768

问题：

我的解释正确吗？
这里有什么问题？这是由于 768.2 与 768 的不准确？如果是，谁让Xcode使用717？我告诉 {Q.width} 是 {W.width}/[14:15]

在此感谢任何帮助！

编辑

以下是三个约束条件：

Answer 1

冲突约束列表包括 h=--& v=--&，这是默认的非自动布局形式。

我尝试使用自动布局获取初始大小和位置，然后尝试通过设置 translatesAutoresizingMaskIntoConstraints=YES 关闭自动布局。我在 Apple 开发者论坛上得到了一个答案，说在这种情况下我需要删除视图的所有约束，可能是从超级视图中删除并添加回去。

提示

在调查这个错误时，我找到了一种使约束冲突日志更容易理解的方法。问题是视图显示为匿名，仅指定 class 而未指定名称。

为了使您的视图可识别，打开您的一个 .m 文件并为您想要识别的每个视图添加一个新的 class，就像这样:

@interface ImgWhiteBar: UIImageView
@end
@implementation ImgWhiteBar
@end    

@interface Spacer1: UIView
@end
@implementation Spacer1
@end

之后，在InterfaceBuilder中，select每个视图，然后在"Identity Inspector"右边修改泛型class（UIVIew，UIImageView等）成其中之一class是您刚刚创建的。

现在再次运行和 Abracadabra - 所有视图现在都用它们的自定义 class 标识，让您了解那里发生了什么。

祝你调试约束愉快！

iOS "Unable to simultaneously satisfy constraints"

iOS "Unable to simultaneously satisfy constraints"

constraints

ios

autolayout

ios-autolayout