在生产中捕获UIViewAlertForUnsatisfiableConstraints

Question

是否有可能在生产中捕获自动布局约束模糊 - 相当于UIViewAlertForUnsatisfiableConstraints断点,但对于生产应用程序？

我的目标是添加一个全局处理程序,将此类错误报告给日志记录系统.

Answer 1

符号UIViewAlertForUnsatisfiableConstraints实际上是一个函数:

_UIViewAlertForUnsatisfiableConstraints(NSLayoutConstraint* unsatisfiableConstraint, NSArray<NSLayoutConstraint*>* allConstraints).

它是私人的,所以你无法取代它.

但它是从私人方法调用的-[UIView engine:willBreakConstraint:dueToMutuallyExclusiveConstraints:],可以调整.此方法大致包含以下内容:

void -[UIView engine:willBreakConstraint:dueToMutuallyExclusiveConstraints:] {
  if ([self _isUnsatisfiableConstraintsLoggingSuspended]) {
    [self _recordConstraintBrokenWhileUnsatisfiableConstraintsLoggingSuspended:$arg4]; // add constraint to some pool
  }
  else {
    if (__UIConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints) {
      // print something in os_log
    }
    else {
      _UIViewAlertForUnsatisfiableConstraints($arg4, $arg5);
    }
  }
}

如果我从这篇文章中理解正确,__UIConstraintBasedLayoutVisualizeMutuallyExclusiveConstraints将始终在iOS上返回NO,所以您需要做的就是检查_isUnsatisfiableConstraintsLoggingSuspended调用的私有bool属性然后调用原始方法.

这是结果代码示例:

#import <objc/runtime.h>

void SwizzleInstanceMethod(Class classToSwizzle, SEL origSEL, Class myClass, SEL newSEL) {
  Method methodToSwizzle = class_getInstanceMethod(classToSwizzle, origSEL);
  Method myMethod = class_getInstanceMethod(myClass, newSEL);
  class_replaceMethod(classToSwizzle, newSEL, method_getImplementation(methodToSwizzle), method_getTypeEncoding(methodToSwizzle));
  class_replaceMethod(classToSwizzle, origSEL, method_getImplementation(myMethod), method_getTypeEncoding(myMethod));
}

@interface InterceptUnsatisfiableConstraints : NSObject
@end

@implementation InterceptUnsatisfiableConstraints

+ (void)load {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    SEL willBreakConstantSel = NSSelectorFromString(@"engine:willBreakConstraint:dueToMutuallyExclusiveConstraints:");
    SwizzleInstanceMethod([UIView class], willBreakConstantSel, [self class], @selector(pr_engine:willBreakConstraint:dueToMutuallyExclusiveConstraints:));
  });
}

- (void)pr_engine:(id)engine willBreakConstraint:(NSLayoutConstraint*)constraint dueToMutuallyExclusiveConstraints:(NSArray<NSLayoutConstraint*>*)layoutConstraints {
  BOOL constrainsLoggingSuspended = [[self valueForKey:@"_isUnsatisfiableConstraintsLoggingSuspended"] boolValue];
  if (!constrainsLoggingSuspended) {
    NSLog(@"_UIViewAlertForUnsatisfiableConstraints would be called on next line, log this event");
  }
  [self pr_engine:engine willBreakConstraint:constraint dueToMutuallyExclusiveConstraints:layoutConstraints];
}

@end

它适用于iOS 8.2/9/10(它在iOS 8.1中不起作用,所以要小心),但我无法保证.此外,它还可以捕获系统组件中的约束问题,例如键盘/视频播放器/等.此代码很脆弱(它可能导致任何系统版本更新崩溃,参数更改等),我不建议在生产中使用它(猜测它甚至不会通过自动审查过程).你有最后一个字,但是你被警告了.

但是我认为您可以在内部/外部测试人员的构建中使用它来修复生产前的autolayout中的错误.

注意到您正在使用swift:您可以使用桥接头文件将此代码添加到swift项目中.