iOS13中 UITabBar隐藏线条不起作用问题

//iOS13必须要下面这种方式才有效，

    //去掉TabBar顶部黑色横线

    if(@available(iOS13.0, *)) {

        UITabBarAppearance*tabBarAppearance = [testTabBar.standardAppearancecopy];

        [tabBarAppearancesetBackgroundImage:[UIImagenew]];

        [tabBarAppearancesetShadowColor:[UIColorclearColor]];

        [testTabBarsetStandardAppearance:tabBarAppearance];

    }else{

        [testTabBarsetBackgroundImage:[UIImage new]];

        [testTabBarsetShadowImage:[UIImagenew]];

    }