获取iOS应用中当前处于Activity状态的ViewController

// 获取当前处于activity状态的view controller
- (UIViewController *)activityViewController
{
UIViewController* activityViewController = 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;
}
}
}

NSArray *viewsArray = [window subviews];
if([viewsArray count] > 0)
{
UIView *frontView = [viewsArray objectAtIndex:0];

id nextResponder = [frontView nextResponder];

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

return activityViewController;
}