ZeroDropdownButtonFormField<T> constructor

ZeroDropdownButtonFormField<T>({ Key? key, required List<ZeroDropdownMenuItem<T>>? items, ZeroDropdownButtonBuilder? selectedItemBuilder, T? value, Widget? hint, Widget? disabledHint, required ValueChanged<T?>? onChanged, VoidCallback? onTap, int elevation = 8, TextStyle? style, Widget? icon, Color? iconDisabledColor, Color? iconEnabledColor, double iconSize = 24.0, bool isDense = true, bool isExpanded = false, double? itemHeight, Color? focusColor, FocusNode? focusNode, bool autofocus = false, Color? dropdownColor, InputDecoration? decoration, FormFieldSetter<T>? onSaved, FormFieldValidator<T>? validator, AutovalidateMode? autovalidateMode, double? menuMaxHeight, bool? enableFeedback, AlignmentGeometry alignment = AlignmentDirectional.centerStart, BorderRadius? borderRadius, })

Creates a ZeroDropdownButton widget that is a FormField, wrapped in an InputDecorator.

For a description of the onSaved, validator, or autovalidateMode parameters, see FormField. For the rest (other than decoration), see ZeroDropdownButton.

The items, elevation, iconSize, isDense, isExpanded, autofocus, and decoration parameters must not be null.

Implementation

ZeroDropdownButtonFormField({
  super.key,
  required List<ZeroDropdownMenuItem<T>>? items,
  ZeroDropdownButtonBuilder? selectedItemBuilder,
  T? value,
  Widget? hint,
  Widget? disabledHint,
  required this.onChanged,
  VoidCallback? onTap,
  int elevation = 8,
  TextStyle? style,
  Widget? icon,
  Color? iconDisabledColor,
  Color? iconEnabledColor,
  double iconSize = 24.0,
  bool isDense = true,
  bool isExpanded = false,
  double? itemHeight,
  Color? focusColor,
  FocusNode? focusNode,
  bool autofocus = false,
  Color? dropdownColor,
  InputDecoration? decoration,
  super.onSaved,
  super.validator,
  AutovalidateMode? autovalidateMode,
  double? menuMaxHeight,
  bool? enableFeedback,
  AlignmentGeometry alignment = AlignmentDirectional.centerStart,
  BorderRadius? borderRadius,
  // When adding new arguments, consider adding similar arguments to
  // ZeroDropdownButton.
})  : assert(
        items == null ||
            items.isEmpty ||
            value == null ||
            items.where((ZeroDropdownMenuItem<T> item) {
                  return item.value == value;
                }).length ==
                1,
        "There should be exactly one item with [ZeroDropdownButton]'s value: "
        '$value. \n'
        'Either zero or 2 or more [ZeroDropdownMenuItem]s were detected '
        'with the same value',
      ),
      assert(itemHeight == null || itemHeight >= kMinInteractiveDimension),
      decoration = decoration ?? InputDecoration(focusColor: focusColor),
      super(
        initialValue: value,
        autovalidateMode: autovalidateMode ?? AutovalidateMode.disabled,
        builder: (FormFieldState<T> field) {
          final _ZeroDropdownButtonFormFieldState<T> state =
              field as _ZeroDropdownButtonFormFieldState<T>;
          final InputDecoration decorationArg =
              decoration ?? InputDecoration(focusColor: focusColor);
          final InputDecoration effectiveDecoration =
              decorationArg.applyDefaults(
            Theme.of(field.context).inputDecorationTheme,
          );

          final bool showSelectedItem = items != null &&
              items
                  .where((ZeroDropdownMenuItem<T> item) =>
                      item.value == state.value)
                  .isNotEmpty;
          bool isHintOrDisabledHintAvailable() {
            final bool isDropdownDisabled =
                onChanged == null || (items == null || items.isEmpty);
            if (isDropdownDisabled) {
              return hint != null || disabledHint != null;
            } else {
              return hint != null;
            }
          }

          final bool isEmpty =
              !showSelectedItem && !isHintOrDisabledHintAvailable();

          // An unfocusable Focus widget so that this widget can detect if its
          // descendants have focus or not.
          return Focus(
            canRequestFocus: false,
            skipTraversal: true,
            child: Builder(builder: (BuildContext context) {
              return ZeroDropdownButtonHideUnderline(
                child: ZeroDropdownButton<T>._formField(
                  items: items,
                  selectedItemBuilder: selectedItemBuilder,
                  value: state.value,
                  hint: hint,
                  disabledHint: disabledHint,
                  onChanged: onChanged == null ? null : state.didChange,
                  onTap: onTap,
                  elevation: elevation,
                  style: style,
                  icon: icon,
                  iconDisabledColor: iconDisabledColor,
                  iconEnabledColor: iconEnabledColor,
                  iconSize: iconSize,
                  isDense: isDense,
                  isExpanded: isExpanded,
                  itemHeight: itemHeight,
                  focusColor: focusColor,
                  focusNode: focusNode,
                  autofocus: autofocus,
                  dropdownColor: dropdownColor,
                  menuMaxHeight: menuMaxHeight,
                  enableFeedback: enableFeedback,
                  alignment: alignment,
                  borderRadius: borderRadius,
                  inputDecoration: effectiveDecoration.copyWith(
                      errorText: field.errorText),
                  isEmpty: isEmpty,
                  isFocused: Focus.of(context).hasFocus,
                ),
              );
            }),
          );
        },
      );