获取当前屏幕显示的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;
  }