iOS 开发-修改 UISearchController中 searchBar 的取消按钮颜色

查了很多资料，终于找到了方法，亲测有效，非常方便简单！

 [[UIBarButtonItem appearanceWhenContainedIn:[UISearchBar class], nil]
                      setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor whiteColor], UITextAttributeTextColor,[NSValue valueWithUIOffset:UIOffsetMake(0, 1)],UITextAttributeTextShadowOffset,nil]
                                    forState:UIControlStateNormal];