获取当前屏幕显示的ViewController

- (UIViewController *)getCurrentVC{

UIViewController *result = nil;

UIWindow * window = [[UIApplication sharedApplication] keyWindow];

//app默认windowLevel是UIWindowLevelNormal，如果不是，找到UIWindowLevelNormal的

if (window.windowLevel != UIWindowLevelNormal)

{

NSArray *windows = [[UIApplication sharedApplication] windows];

for(UIWindow * tmpWin in windows)

{

if (tmpWin.windowLevel == UIWindowLevelNormal)

{

window = tmpWin;

break;

}

}

}

id  nextResponder = nil;

UIViewController *appRootVC=window.rootViewController;

//    如果是present上来的appRootVC.presentedViewController 不为nil

if (appRootVC.presentedViewController) {

nextResponder = appRootVC.presentedViewController;

}else{

UIView *frontView = [[window subviews] objectAtIndex:0];

nextResponder = [frontView nextResponder];  ///< style="font-family: Arial, Helvetica, sans-serif;">//  这方法下面有详解

}

if ([nextResponder isKindOfClass:[UITabBarController class]]){

UITabBarController * tabbar = (UITabBarController *)nextResponder;

UINavigationController * nav = (UINavigationController *)tabbar.viewControllers[tabbar.selectedIndex];

//        UINavigationController * nav = tabbar.selectedViewController ; 上下两种写法都行

result=nav.childViewControllers.lastObject;

}else if ([nextResponder isKindOfClass:[UINavigationController class]]){

UIViewController * nav = (UIViewController *)nextResponder;

result = nav.childViewControllers.lastObject;

}else{

result = nextResponder;

}

return result;

}