How to handle the list of dynamic dropdown in flutter?

Question

I need to have the list of add able dropdown of states,district. They can be added. I could add the forms but I need to set the district data according to the states.I get the states from the api. When selecting the states from dropdown I get the districts according to states from api.Its working fine with the district dropdown of index 0 but I am getting the error There should be exactly one item with [DropdownButton]'s value: 1. in other index. How can I achieve this. I followed this https://stackoverflow.com/a/63188955/8023701. I have implemented as follows:

Widget _buildStates(BuildContext context, int i) {
return
    Container(
        width: MediaQuery.of(context).size.width,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.start,
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Text(
              state,
              style: TextStyle(
                  //  fontSize: 18,
                  fontWeight: FontWeight.bold,
                  color: Colors.red),
            ),
            SizedBox(
              width: 20,
            ),
            DropdownButtonFormField(

              validator: (value) => validateDrops(value),
              isExpanded: true,
              hint: Text(state),
              value: _selectedState[i],
              onChanged: (newValue) {
                setState(() {
                  print("Stae value");
                  print(newValue);
                  _selectedState[i]= newValue;
                  getMyDistricts(newValue, i);
                });
        
              },
              items: statess.map((Data item) {
                return new DropdownMenuItem(
                  child: new Text(
                    item.provinceNepali,
                  ),
                  value: item.id.toString(),
                );
              }).toList(),
            )
          ],
        
        ));
 }

District widget:

Widget _buildDistrict(BuildContext context, int i) {
return Container(
    width: MediaQuery.of(context).size.width,
    child: Column(
      mainAxisAlignment: MainAxisAlignment.start,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Text(
          district,
          style: TextStyle(
              //  fontSize: 18,
              fontWeight: FontWeight.bold,
              color: Colors.red),
        ),
        SizedBox(
          width: 20,
        ),
        mydis != null
            ? DropdownButtonFormField(
                validator: (value) => validateDrops(value),
                isExpanded: true,
                hint: Text(select),
                value: _selectedDistrict[i],
                onChanged: (newValue) {
                  setState(() {
                    _selectedDistrict[i] = newValue;
                    getMyMuni(newValue, i);
                  });
                },
                items: mydis.map((Datas item) {
                  return new DropdownMenuItem(
                    child: new Text(
                      item.municipalityEnglish,
                    ),
                    value: item.id.toString(),
                  );
                }).toList(),
              )
            : Container()
      ],
    ));
}

I am getting states from api as follows:

 void getAvgProvince() async {
    setState(() {
      _isLoading = true;
    });
    ProvinceResponse joinResponse = await getProvince();

    if (joinResponse != null) {
      setState(() {
        statess = joinResponse.data;
        _isLoading = false;
      });
    } else {
      setState(() {
        _isLoading = false;
      });
    }
  }

And district as follows:

 void getMyDistricts(newValue, int i) async {
DistrictResponse joinResponse = await getDistrict(newValue);

if (joinResponse != null) {
  setState(() {

    mydis = joinResponse.data;
    _isLoading = false;
  });
} else {
  setState(() {
    _isLoading = false;
  });
}
}

score 0 · Answer 1 · answered Jul 25 '22 at 16:18

The DropdownButton error There should be exactly one item with [DropdownButton]'s value: 1 occurs because the initial selected value of the dropdown is null. What you can do here is add a placeholder value for the dropdown if it's yet to be active. You can follow a similar approach on this answer.

How to handle the list of dynamic dropdown in flutter?

1 Answers1