显示长列表的Listview else语句

我已经创建了一个列表视图。当我应用过滤器时，我只想显示特定条件下的数据。如果条件中不存在任何项目，我希望显示一条文字，并显示一条消息，说明“现在没有预订”

我一切都很好，但“现在没有预订”多次出现在列表中。我只想显示一次

我的代码在下面

                    : ListView.builder(
                itemCount: _bookingData.bookingData == null
                    ?  Center(child: CircularProgressIndicator(),)
                    : _bookingData.bookingData.length,
                shrinkWrap: true,
                itemBuilder: (BuildContext context, int index) {
                  return
                    GestureDetector(
                      onTap: (){Navigator.push(context, MaterialPageRoute(builder: (context)=>BookingDetails(_bookingData.bookingData[index]
                      )));},
                      child: (widget.formattedDate == null&&widget.bookId == null) ?
                               // List()


                      ListPopUP(_bookingData.bookingData[index])




                          : ((widget.formattedDate != null&&(_bookingData.bookingData[index].date.toString().contains(widget.formattedDate)))?





                      ListPopUP(_bookingData.bookingData[index]):





                      (widget.bookId != null&&_bookingData.bookingData[index].bookingId.toString().contains(widget.bookId))?





                      ListPopUP(_bookingData.bookingData[index]):




                      Container(
                        child: Text("NO BOOKING NOW"),
                      )),
                    ) ;

                })),
      )
    ],
  ),
);
}

---

不管你的情况如何，我暂时认为这是一种表现

bool show = false;
    int n = 10;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: show?ListView.builder(
        itemCount: n,
        itemBuilder: (BuildContext context, int index) {
          return Container(
              child: Text('Your statement you wanted')
            ),
          );
        },
      ):Container(
                        child: Text("NO BOOKING NOW"),
                      ),