flutter dropdownbutton issue with provider statemangement

Question

hello guys as a beginner on flutter i'm having an issue with the dropdownbutton widget as shown on the joined GIF

on the backend everything seems to work normally every row n the list has it Answer properly but on the screen the values changes for the whole screen not row by row that's the source code for the ChangeNotifier() :

class ChoiceHandler extends ChangeNotifier {
  final List<String> _dropdownElements = ['Not Done', 'Partially Done', 'Done'];
  List<String> get dropdownElement => _dropdownElements;
  late String _selectedItemValue;
  String get selected => _selectedItemValue;

  selectedValues(String s) {
    _selectedItemValue = s;
    notifyListeners();
  }
}

and under listView here is the code for the dropdownButton :

Expanded(
            child: ListView.builder(
              itemCount: propositions.length,
              itemExtent: 50.0,
              itemBuilder: (BuildContext context, int index) {
                return ListTile(
                    title: Text(propositions[index]),
                    trailing: Consumer<ChoiceHandler>(
                      builder: (_, provider, __) {
                        return DropdownButton<String>(
                          value: dropdownValue,
                          onChanged: (newValue) {
                            provider.selectedValues(newValue as String);
                            dropdownValue = newValue;
                            print((propositions[index]) + "  " + newValue); // here i can the results when i'm changing values
                          },
                          items: provider.dropdownElement
                              .map<DropdownMenuItem<String>>((String value) {
                            return DropdownMenuItem<String>(
                              value: value,
                              child: Text(value),
                            );
                          }).toList(),
                        );
                      },
                    ) //_dropdown(index),
                    );

thanks in advance

Answer 1

i've found the issue i've misplaced the declaration of a veriable ,th variable "dropdownValue" was declared above as a global variable , and then i've changed it place to where it's shown on the source code :

child: ListView.builder(
              itemCount: propositions.length,
              itemExtent: 50.0,
              itemBuilder: (BuildContext context, int index) {
              String dropdownValue = "Not Done"; // <==== i declared it here
                return ListTile(
                    title: Text(propositions[index]),
                    trailing: Consumer<ChoiceHandler>(
                      builder: (_, provider, __) {
                        return DropdownButton<String>(
                          value: dropdownValue,
                          onChanged: (newValue) {
                            provider.selectedValues(newValue as String);
                            dropdownValue = newValue;
                            print((propositions[index]) + "  " + newValue); 
                          },
                          items: provider.dropdownElement
                              .map<DropdownMenuItem<String>>((String value) {
                            return DropdownMenuItem<String>(
                              value: value,
                              child: Text(value),
                            );
                          }).toList(),
                        );
                      },
                    ) //_dropdown(index),
                    );