Question 245554 in Flutter Question posted in
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How to validate DropdownButtomFormFeild in flutter using formkey

I am new to flutter I am trying to create a large form, where I am using form key to validate form and global object to store value using on Saved method on TextFormFeild of flutter how can i do same thing with DropdownButtonFormField.

Specifically, i don’t want to use DropdownButtonFormFeild onChanged method instead i want to do it using onSaved method.

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2

Answers


  1. 0

    If you can use validator on TextFormField, then you can use it on dropdown too.

    Wrap with Form, add formKey then just trigger the validation with button.

    Example:

      DropdownButtonFormField<String>(
                items: items,
                onChanged: onChanged,
                validator: (e){
                  if (e == null){
                    return "ERROR";
                  }
                  return null ; 
                },
              ),

    You can use validator like commong TextFormField

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  2. 0

    Try this:

    class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  GlobalKey<FormState> formKey = GlobalKey<FormState>();
  String? selectedItem;

  @override
  void dispose() {
    formKey.currentState?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Form(
          key: formKey,
          child: Column(
            children: <Widget>[
              DropdownButtonFormField<String>(
                value: selectedItem,
                hint: const Text("Select"),
                items: const <String>[
                  "A",
                  "B",
                ].map<DropdownMenuItem<String>>(
                  (String value) {
                    return DropdownMenuItem<String>(
                      value: value,
                      child: Text(value),
                    );
                  },
                ).toList(),
                onSaved: (String? value) {
                  selectedItem = value;
                  setState(() {});
                },
                validator: (String? value) {
                  return value == null ? "Required" : null;
                },
              ),
              ElevatedButton(
                onPressed: () {
                  if (formKey.currentState?.validate() ?? false) {
                    // Valid form
                  } else {
                    // Invalid form
                  }
                },
                child: const Text("Submit"),
              )
            ],
          ),
        ),
      ),
    );
  }
}
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