Question 76446 in Flutter Question posted in
The official Flutter documentation can be found here.

How to assign initial value in DropdownButton in Flutter..?

suppose you a List of String List which will come from API.
now you want to show that list inside DropdownButton.
Let’s say your list is like

homepage_categories": [
    {
    "id": 1,
    "name": "Electronics",
    "slug": "electronics",
    "icon": "fas fa-anchor",
    "image": "uploads/custom-images/electronics-2022-11-19-02-48-28-5548.png"
    },
    {
    "id": 2,
    "name": "Game",
    "slug": "game",
    "icon": "fas fa-gamepad",
    "image": "uploads/custom-images/game-2022-11-19-02-48-48-6382.png"
    },
    {
    "id": 3,
    "name": "Mobile",
    "slug": "mobile",
    "icon": "fas fa-mobile-alt",
    "image": "uploads/custom-images/mobile-2022-11-19-02-49-20-2538.png"
    },
    {
    "id": 4,
    "name": "Lifestyle",
    "slug": "lifestyle",
    "icon": "fas fa-home",
    "image": "uploads/custom-images/lifestyle-2022-11-19-02-49-38-3139.png"
    },
]

From this API you can easily fetch.

So the Question is How can i assign a default/initial value like Select Category or something else into that list

I have tried this…

    late List<CategoryModel> category;
  late String value;

  @override
  void initState() {
    category = context.read<CategoryBrandCubit>().categoryBrandModel.category;
    value = category.first.id.toString();
    super.initState();
  }


DropdownButton<String>(
          hint: const Text('Select Status'),
          isExpanded: true,
          icon: const Icon(Icons.keyboard_arrow_down_rounded),
          underline: const SizedBox(),
          value: value,
          onChanged: (String? val) {
            value = val!;
            bloc.add(StoreProductEventCategory(value));
            print('catVal: $value');
          },
        
          items: category
              .map(
                (e) => DropdownMenuItem<String>(
                  value: e.id.toString(),
                  child: Text(e.name),
                ),
              )
              .toList(),
        ),
Tags:

2

Answers


  1. 0

    try this:

    DropdownButton<String>(
                            hint: const Text('Select Status'),
                            isExpanded: true,
                            icon: const Icon(
                                Icons.keyboard_arrow_down_rounded),
                            underline: const SizedBox(),
                            value: "default",
                            onChanged: (String? val) {},
                            items: [
                              const DropdownMenuItem(
                                alignment: Alignment.center,
                                value: "default",
                                enabled: false,
                                child: Text("Select Your role"),
                              ),
                              ...category
                                  .map(
                                    (e) => DropdownMenuItem<String>(
                                      value: e.id.toString(),
                                      child: Text(e.name),
                                    ),
                                  )
                                  .toList()
                            ],
                          ),
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  2. 0

    The DropdownButton default value is corrosponding to the value field. If we take a look at your code we see that you assign value but it is empty:

    late String value; // this is empty

DropdownButton<String>(
          hint: const Text('Select Status'),
          isExpanded: true,
          icon: const Icon(Icons.keyboard_arrow_down_rounded),
          underline: const SizedBox(),
          value: value, // always the current value
          onChanged: (String? val) {
            value = val!;
            bloc.add(StoreProductEventCategory(value));
            print('catVal: $value');
          },

    What you have to do is asigning an initial value to value. You could do something like: value = homepage_categories[0].name

    If you take a look at the official flutter documentation you can also see that the value field is described as the following:

    value → T?: The value of the currently selected DropdownMenuItem.

    You can read more about it here and see the full example.

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