使用 UIViewAlertForUnsatisfiableConstraints 捕捉autolayout 约束冲突

最新推荐文章于 2021-02-03 14:04:11 发布

阿飞正传的阿飞

最新推荐文章于 2021-02-03 14:04:11 发布

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分类专栏： iOS 文章标签：苹果调试布局 autolayout

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在iOS开发中，当遇到AutoLayout约束冲突时，苹果提供的解决方案是在log中查看错误信息。然而，这些信息通常难以理解和定位问题。通过设置symbolic breakpoint，我们可以更有效地调试。只需在断点管理界面添加一个symbolic breakpoint，符号填写为UIViewAlertForUnsatisfiableConstraints，一旦发生约束冲突，程序将在该断点暂停，从而方便开发者排查问题。了解更多断点技巧，可以查阅Cocoa的相关文章。

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很多时候我们会遇到约束冲突的问题、但是因为苹果只会在log中提示冲突、且这些冲突很难去理解、所以遇到冲突、也很难发现到底是哪里出了问题、但是苹果还是提供了方法、去debug的。
我们来看冲突的log：

2015-08-26 14:29:32.870 Auto Layout Cookbook[10208:1918826] 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:0x7b58bac0 'Label Leading' UILabel:0x7b58b040'Name'.leading == UIView:0x7b590790.leadingMargin>",
    "<NSLayoutConstraint:0x7b56d020 'Label Width' H:[UILabel:0x7b58b040'Name'(>=400)]>",
    "<NSLayoutConstraint:0x7b58baf0 'Space Between Controls' H:[UILabel:0x7b58b040'Name']-(NSSpace(8))-[UITextField:0x7b589490]>",
    "<NSLayoutConstraint:0x7b51cb10 'Text Field Trailing' UITextField:0x7b589490.trailing == UIView:0x7b590790.trailingMargin>",
    "<NSLayoutConstraint:0x7b0758c0 'UIView-Encapsulated-Layout-Width' H:[UIView:0x7b590790(320)]>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x7b56d020 'Label Width' H:[UILabel:0x7b58b040'Name'(>=400)]>

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.

里面写了

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.

这就意味着、我们可以通过symbolic breakpoint 来捕捉冲突、如何来设定呢？平时管理断点的地方、点击加号、addMake a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.然后在symbol内容填上UIViewAlertForUnsatisfiableConstraints、如果出现冲突、系统会自动停留在断点处、还是蛮好用的。
这里写图片描述