flutter dropdown menu items error when list is empy-CodePudding

I try to fill dropdown menu items from api json. I have "mylist" in code. Sometimes, this list is empty and sometimes list has data.

if myList has data there is no problem. I am having trouble when myList is empty. How can i sove this.

 items: _loginController.loginList[0].myList
          .where((p0) => p0.callType == 1)
          .map(
            (item) => DropdownMenuItem<String>(
              value: item.callId.toString(),
              child: Text(
                item.callId.toString(),
                style: GoogleFonts.ptSansNarrow(
                  textStyle: TextStyle(
                      fontSize: 25,
                      fontWeight: FontWeight.w600,
                      color: Colors.black.withOpacity(.8)),
                ),
              ),
            ),
          )
          .toList(),

CodePudding user response：

You can try this:

var _list = _loginController.loginList[0].myList;
DropdownButton(
    items:_list.isEmpty ? [] : _list.where((p0) => p0.callType == 1)
      .map(
        (item) => DropdownMenuItem<String>(
          value: item.callId.toString(),
          child: Text(
            item.callId.toString(),
            style: GoogleFonts.ptSansNarrow(
              textStyle: TextStyle(
                  fontSize: 25,
                  fontWeight: FontWeight.w600,
                  color: Colors.black.withOpacity(.8)),
            ),
          ),
        ),
      )
      .toList(),
    onChanged: (_) {},
  ),

CodePudding user response：

make your value nullable you would no longer be able to access the dropdown button if no items are available in the list by default it will be disabled

class _MyHomePageState extends State<MyHomePage> {
  String? val; //default value


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: DropdownButton(
          onChanged: (value){},
          value: val, // this is where you need to access it
          items: [].map((e) {
            return DropdownMenuItem(
            value: e,
              child: Text(e),
            )
              ;
          }).toList(),
        
        )));
  }
}