ios-获取当前正在显示的ViewController

我们在非视图类中想要随时展示一个view时，需要将被展示的view加到当前view的子视图，或用当前view presentViewController，或pushViewContrller，这些操作都需要获取当前正在显示的ViewController。

//获取当前屏幕显示的viewcontroller
- (UIViewController *)getCurrentVC
{
UIViewController *result = nil;

UIWindow * window = [[UIApplication sharedApplication] keyWindow];
if (window.windowLevel != UIWindowLevelNormal)
{
NSArray *windows = [[UIApplication sharedApplication] windows];
for(UIWindow * tmpWin in windows)
{
if (tmpWin.windowLevel == UIWindowLevelNormal)
{
window = tmpWin;
break;
}
}
}

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

if ([nextResponder isKindOfClass:[UIViewController class]])
result = nextResponder;
else
result = window.rootViewController;

return result;
}