一、添加断点定位
1、添加UIViewAlertForUnsatisfiableConstraints断点
- 添加Symbolic Breakpoints
- 编辑断点symbol填入
UIViewAlertForUnsatisfiableConstraints
- 添加控制台打印action
po [[UIWindow keyWindow] _autolayoutTrace]
2、定位约束警告冲突
- 添加好断点之后，当界面有约束冲突，就会触发断点，控制打印如下：
[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.
(
<MASLayoutConstraint:0x604000ab04a0 UIButton:0x7faf99f04010.width == 40>,
<MASLayoutConstraint:0x604000ab66e0 UIButton:0x7faf99f04010.left == CYBButtonView:0x7faf99f83360.left + 10>,
<MASLayoutConstraint:0x604000abaa00 UILabel:0x7faf99f5f8e0.left == UIButton:0x7faf99f04010.right>,
<MASLayoutConstraint:0x604000abd580 UILabel:0x7faf99f5f8e0.left == CYBButtonView:0x7faf99f83360.left + 15>,
)
Will attempt to recover by breaking constraint
<MASLayoutConstraint:0x604000ab04a0 UIButton:0x7faf99f04010.width == 40>
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.
- 根据提示，找到约束有问题的控件地址0x7faf99f04010，然后全局搜索，就能找到具体是哪个控件
- 如果控制台打印不够直观看出是哪个控件约束有问题，我们可以通过 LLDB命令工具chisel定位寻找。
二、Masonry Key 调试
冲突的autolayout 加上key后输出信息为:
make.right.and.bottom.equalTo(-20);
make.right.and.bottom.equalTo(-30).key(@"TestForKey");
"<MASLayoutConstraint:0x126695170 UIView:0x126696bf0.right == UIView:0x12654ca70.right - 20>",
"<MASLayoutConstraint:TestForKey[0] UIView:0x126696bf0.right == UIView:0x12654ca70.right - 30>"
将类的地址换成了 加的key 这样的输出在调试时能很容易发现错误标记
MASAttachKeys(redView);
三、lldb调试
此时我们只需要点击调试图层按钮,就可以进行命令执行了，不仅可以查看图层，打印视图信息，查看某个视图地址，还可以在 lldb 执行命令。
20210114111433963.png
根据系统要删除的约束的控件地址，
比如转化地址对象并输出属性
(lldb) po ((UIView *)0x7fb43d20a6e0).subviews
<__NSArrayM 0x6000033baaf0>(
<UILabel: 0x7fb43d20a850; frame = (22 35; 42 21); text = 'Label'; opaque = NO; autoresize = RM+BM; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x600001efcb40>>
)
通过打印子视图就可以看见 view 下面包含Label控件，从而方便定位。
根据地址转对象，打印子视图层级
我们通过打印图层层级就可以很容易判断冲突控件属于哪个 View
po [((UIView *)0x7fa5382061c0) recursiveDescription]
四、解决冲突
通常解决冲突的方法有：
- 删除多余约束
- 修改约束优先级
