Select and multi-select

A dropdown over a single-select controller, and a chip group over a multi-select one, both with a label and an error slot.

Both controllers carry their options, so the widget only asks the field what to list and what is selected. An InputDecorator gives either widget a label and an errorText, and — unlike a form-field dropdown seeded with an initial value — always reflects the field's current value, including after reset().

select_input.dartidle

Source3 files

dropdown_input.dart

class _DropdownInput<V> extends StatelessWidget {
  const _DropdownInput({required this.field, required this.label});

  final AdvancedSingleSelectFieldController<V, String> field;
  final String label;

  @override
  Widget build(BuildContext context) {
    return AdvancedFieldBuilder<V?, String>(
      field: field,
      builder: (context, state, _) => Padding(
        padding: const EdgeInsets.symmetric(vertical: 6),
        child: InputDecorator(
          decoration: InputDecoration(labelText: label, errorText: state.error),
          isEmpty: state.value == null,
          child: DropdownButtonHideUnderline(
            child: DropdownButton<V>(
              value: state.value,
              isExpanded: true,
              isDense: true,
              focusNode: field.focusNode,
              items: [
                for (final option in field.options)
                  DropdownMenuItem(value: option, child: Text('$option')),
              ],
              onChanged: state.readOnly ? null : field.select,
            ),
          ),
        ),
      ),
    );
  }
}

DocsActions is a shorthand these docs define, not part of the package. See Rendering fields for the widget code an app writes.

field.select(option) and field.toggleElement(option) are the setters; both are no-ops while read-only, which is why the widgets null their callbacks on state.readOnly rather than calling getValueSetter(). select asserts in debug builds that the option is one of options; select(null) clears and is always allowed.

DropdownButtonFormField and Flutter versions

Its selected-value parameter is value: up to Flutter 3.33 and initialValue: from 3.35 on. DropdownButton inside an InputDecorator, as above, compiles on every version.

Edit on GitHub