//在appdelegate    获取rootVC

        ZFTabBarViewController *rootVC = (ZFTabBarViewController *)[UIApplication sharedApplication].keyWindow.rootViewController;

    //取到当前展示的tabbar   selectedindex 在哪

        ZFNavViewController*navigationVC = rootVC.selectedViewController;

//获取root  present出来的VC

        ZFNavViewController *navVC = (ZFNavViewController *)[UIApplication sharedApplication].keyWindow.rootViewController.presentedViewController;

if ([[UIApplication sharedApplication].keyWindow.rootViewController.presentedViewController  isKindOfClass:[ZFNavViewController class]]) {

            [navVC.visibleViewController.navigationController popToRootViewControllerAnimated:NO];

   [navVCdismissViewControllerAnimated:YES completion:nil];            rootVC.selectedIndex=0;

//                [[UIApplication sharedApplication].keyWindow.rootViewController.presentedViewController presentViewController:alertAction animated:YES completion:nil];

        }else{

            [navigationVC.visibleViewController.navigationController popToRootViewControllerAnimated:NO];

        }

        [[UIApplication sharedApplication].keyWindow.rootViewController presentViewController:alertAction animated:YES completion:nil];