SignalDropdown<T> class

A reactive DropdownButtonFormField bound to a Field<T>.

Writes the selected item's value to field.value and calls Field.touch on selection. Field.error appears as InputDecoration.errorText once the field is touched.

T is the type of the selected dropdown value. field is the backing Field<T>. items is the list of DropdownMenuItem entries shown in the overlay. decoration wraps the dropdown button with a Material InputDecoration. hint is shown when no value is selected (placeholder). disabledHint is shown instead of hint when enabled is false. onChanged is called after field.value is updated on each selection. onTap fires when the user taps the dropdown button (before the overlay opens). enabled — when false, the dropdown is read-only and visually dimmed. focusNode overrides the internally managed FocusNode.

Example:

final country = Field<String>('country')
  ..required(message: 'Selecione um país');

SignalDropdown<String>(
  field: country,
  decoration: const InputDecoration(labelText: 'País'),
  hint: const Text('Selecione...'),
  items: const [
    DropdownMenuItem(value: 'BR', child: Text('Brasil')),
    DropdownMenuItem(value: 'US', child: Text('Estados Unidos')),
    DropdownMenuItem(value: 'PT', child: Text('Portugal')),
  ],
)