iOS 获取当前的ViewController的方法

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

+ (UIViewController *)getCurrentViewController {
  UIViewController *result = nil;
  UIWindow * window = [[UIApplication sharedApplication] keyWindow];
  //app默认windowLevel是UIWindowLevelNormal，如果不是，找到它
  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;
  //1、通过present弹出VC，appRootVC.presentedViewController不为nil
  if (appRootVC.presentedViewController) {
    nextResponder = appRootVC.presentedViewController;
  }else{
    //2、通过navigationcontroller弹出VC
    NSLog(@"subviews == %@",[window subviews]);
    UIView *frontView = [[window subviews] objectAtIndex:0];
    nextResponder = [frontView nextResponder];
  }
  //1、tabBarController
  if ([nextResponder isKindOfClass:[UITabBarController class]]){
    UITabBarController * tabbar = (UITabBarController *)nextResponder;
    UINavigationController * nav = (UINavigationController *)tabbar.viewControllers[tabbar.selectedIndex];
    //或者 UINavigationController * nav = tabbar.selectedViewController;
    result = nav.childViewControllers.lastObject;
  }else if ([nextResponder isKindOfClass:[UINavigationController class]]){
    //2、navigationController
    UIViewController * nav = (UIViewController *)nextResponder;
    result = nav.childViewControllers.lastObject;
  }else{//3、viewControler
    result = nextResponder;
  }
  return result;
}