A simple segmented control form field for flutter.

segmented_control_form_field.dart

import 'package:flutter/material.dart';

class SegmentedControlFormField extends FormField<int> {
  final List<String> options;
  final double textScaleFactor;

  SegmentedControlFormField({
    this.options,
    this.textScaleFactor,
    FormFieldSetter<int> onSaved,
    FormFieldValidator<int> validator,
    int initialValue = 0,
    bool autovalidate = false,
  }) : super(
          onSaved: onSaved,
          validator: validator,
          initialValue: initialValue,
          autovalidate: autovalidate,
          builder: (FormFieldState<int> state) {
            return Container(
              padding: const EdgeInsets.symmetric(horizontal: 2),
              decoration: BoxDecoration(
                color: swatch.shade500,
                borderRadius: BorderRadius.circular(2),
              ),
              child: Row(
                children: options.map<Widget>(
                  (String option) {
                    return Expanded(
                      child: Padding(
                        padding: const EdgeInsets.symmetric(
                            vertical: 4, horizontal: 2),
                        child: Stack(
                          alignment: Alignment.center,
                          children: <Widget>[
                            GestureDetector(
                              onTap: () {
                                state.didChange(options.indexOf(option));
                              },
                              child: AnimatedContainer(
                                height: 48,
                                duration: Duration(milliseconds: 100),
                                decoration: BoxDecoration(
                                  color: options.indexOf(option) == state.value
                                      ? swatch.shade100
                                      : swatch.shade500,
                                  borderRadius: BorderRadius.circular(2),
                                ),
                              ),
                            ),
                            IgnorePointer(
                              child: Text(
                                option,
                                style: TextStyle(
                                    color:
                                        options.indexOf(option) == state.value
                                            ? Colors.black
                                            : Colors.white),
                                textScaleFactor: textScaleFactor,
                                softWrap: false,
                                overflow: TextOverflow.fade,
                              ),
                            ),
                          ],
                        ),
                      ),
                    );
                  },
                ).toList(growable: false),
              ),
            );
          },
        );
}