我已经创建了PageViewBuilder来显示我的列表项...当我到达列表的最后一项时...我想显示一个隐藏的小部件如何实现？
这是当我到达列表的最后一个项目时要显示的小部件

Expanded(
                  flex: 3,
                  child: Container(
                    height: 40,width: 40,
                      color: Colors.black87,
                      child: MaterialButton(onPressed: (){},child: Text('Done',style: TextStyle(
                        fontSize: 20,fontWeight: FontWeight.w500,color: Colors.white
                      ),),)),

下面是我完整代码

class _getPlanExDetails2ScreenState extends State<getPlanExDetails2Screen> {
  

  @override
  Widget build(BuildContext context) {
    return BlocConsumer<LifeStyleCubit,LifeStates>(
      listener: (context,state)
      {},
      builder: (context,state)
      {
        var cubit = LifeStyleCubit.get(context);
        return Scaffold(
          appBar: AppBar(
            elevation: 0,
            title: Text('Exercise'),
          ),
          body: PageView.builder(
            itemBuilder: (BuildContext context,index) => letsTest(cubit.PlanDaysExList[index],context,index),
            itemCount: cubit.PlanDaysExList.length,
            scrollDirection: Axis.horizontal,
            controller: widget.pageController,
            ),
          bottomNavigationBar: Padding(
            padding: const EdgeInsets.only(bottom:20,right: 75,left: 75 ),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Expanded(
                  child: Container(
                    height: 40,width: 40,
                      child: MaterialButton(onPressed: ()
                      {
                        widget.pageController.previousPage(duration:Duration(milliseconds: 500),
                            curve: Curves.easeInOut);
                      },child: Icon(IconBroken.Arrow___Left_2
                      ,color: Colors.white,),)),
                ),
                Expanded(
                  flex: 3,
                  child: Container(
                    height: 40,width: 40,
                      color: Colors.black87,
                      child: MaterialButton(onPressed: (){},child: Text('Done',style: TextStyle(
                        fontSize: 20,fontWeight: FontWeight.w500,color: Colors.white
                      ),),)),   // i need to show this widget when i reach to the last index of the list
                ),
                Expanded(
                  child: Container(
                    height: 40,width: 20,
                      child: MaterialButton(onPressed: ()
                      {
                        widget.pageController.nextPage(duration:Duration(milliseconds: 500),
                            curve: Curves.easeInOut);
                      },child: Icon(IconBroken.Arrow___Right_2
                      ,color: Colors.white,),)),
                ),
              ],
            ),
          ),
        );
      },
    );
  }

我尝试用Visiblity小部件 Package 它并使用setState，但失败了