获取rootViewController 的两种方式分别是：

UIViewController *root=  [[UIApplication sharedApplication] keyWindow].rootViewController;

AppDelegate appdelegate=(AppDelegate)[UIApplication sharedApplication].delegate;
UIViewController *rooViewController= [appdelegate window].rootViewController;

image.png

当UIAlertView ,ActionSheet 代理方法之后调用1.root 对象UIApplicationRotationFollowingController，2. rooViewController依然是你设置的windows.rootViewController