实际开发中，时长需要获取屏幕最上层的ViewController，以下代码是对实现此需求的简单代码封装。
PS:以下代码被封装为UIApplication类的分类
<pre>
`
//获取rootViewController
- (UIViewController )rootViewController{
UIWindow window = [UIApplication sharedApplication].keyWindow;
return window.rootViewController;
}
`
</pre>
<pre>
`
//获取Window当前显示的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>
