Flutter：下拉按钮未更新以显示所选选项

Question

I am trying to use a dropdown button to have the user select from a list of options, however after making a selection the dropdown button remains displaying the hint. I think something about the setState is not updating the dropdown button.

              value: skillChoice,
              items: listDrop,
              hint: Text("Choose Skill"),
              onChanged: (value) {

                setState(() {
                  skillChoice = value;
                });
              },
            ),

here are the variables which are declared earlier in the code:

      List<DropdownMenuItem<int>> listDrop = [];
      int skillChoice = null;

Can anyone let me know why it isn't updating?

Answer 1

I think setting skillChoice null initially disables the dropdown.

Answer 2

It would have been better if you had shown the full code snippet of how you implemented your DropDownButton. But here is how I do implement mine:

 // This is the initial value that will be selected on the DropDownMenu by default

    String choice = '1';


    // This is the List of String (or whatever data type you want) that will make up the 
    Drop Down Menu Item options. NOTE: That the String value of 'choice' ('1') is also present in the List of choices ('1')

    List<String> choices = [
    '1',
    '2',
    '3',
    '4',
    '5',
    ];

    DropdownButton<String>(
                value: choice,
                icon: Icon(Icons.add),
                onChanged: (String newValue) {
                  setState(() => choices = newValue);
                },
                items: choices.map<DropdownMenuItem<String>>((String value) {
                  return DropdownMenuItem<String>(
                    value: value,
                    child: Text(
                          value,
                        )
                  );
                }).toList(),
              ),

Should work properly for you now.