實際開發(fā)中，時長需要獲取屏幕最上層的ViewController，以下代碼是對實現(xiàn)此需求的簡單代碼封裝。

PS:以下代碼被封裝為UIApplication類的分類

<pre>
`
//獲取rootViewController

• (UIViewController )rootViewController{
  UIWindow window = [UIApplication sharedApplication].keyWindow;
  return window.rootViewController;
  }
  `
  </pre>

<pre>
`
//獲取Window當前顯示的ViewController

• (UIViewController)currentViewController{
  UIViewController vc = [UIApplication rootViewController];

  while (1) {
  if ([vc isKindOfClass:[UITabBarController class]]) {
  vc = ((UITabBarController*)vc).selectedViewController;
  }

    if ([vc isKindOfClass:[UINavigationController class]]) {
        vc = ((UINavigationController*)vc).visibleViewController;
    }
    
    if (vc.presentedViewController) {
        vc = vc.presentedViewController;
    }else{
        break;
    }
  

  }

  return vc;
  }

`
</pre>