Sample Flutter Likert

main.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// This is the main application widget.
class MyApp extends StatelessWidget {
  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        body: MyStatefulWidget(),
      ),
    );
  }
}

class LabeledRadio extends StatelessWidget {
  const LabeledRadio({
    this.label,
    this.padding,
    this.groupValue,
    this.value,
    this.onChanged,
    this.itemOrder,
  });

  final String label;
  final EdgeInsets padding;
  final int groupValue;
  final int value;
  final Function onChanged;
  final int itemOrder;

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () {
        if (value != groupValue) onChanged(value);
      },
      child: CustomPaint(
        painter: _LinePainter(itemOrder),
        child: Padding(
          padding: padding,
          child: Row(
            children: <Widget>[
              Radio<int>(
                groupValue: groupValue,
                value: value,
                onChanged: (int newValue) {
                  onChanged(newValue);
                },
              ),
              Text(label),
            ],
          ),
        ),
      ),
    );
  }
}

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  MyStatefulWidget({Key key}) : super(key: key);

  @override
  _MyStatefulWidgetState createState() => _MyStatefulWidgetState();
}

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
   int _selectedVal = -1;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <LabeledRadio>[
          LabeledRadio(
            label: 'Strongly Disagree',
            padding: const EdgeInsets.symmetric(horizontal: 5.0),
            value: 2,
            groupValue: _selectedVal,
            onChanged: (int newValue) {
              setState(() {
                _selectedVal = newValue;
              });
            },
            itemOrder: _LinePainter.FIRST_ITEM,
          ),
          LabeledRadio(
            label: 'Disagree',
            padding: const EdgeInsets.symmetric(horizontal: 5.0),
            value: 3,
            groupValue: _selectedVal,
            onChanged: (int newValue) {
              setState(() {
                _selectedVal = newValue;
              });
            },
            itemOrder: _LinePainter.MIDDLE_ITEM,
          ),
          LabeledRadio(
            label: 'Neutral',
            padding: const EdgeInsets.symmetric(horizontal: 5.0),
            value: 4,
            groupValue: _selectedVal,
            onChanged: (int newValue) {
              setState(() {
                _selectedVal = newValue;
              });
            },
            itemOrder: _LinePainter.MIDDLE_ITEM,
          ),
          LabeledRadio(
            label: 'Agree',
            padding: const EdgeInsets.symmetric(horizontal: 5.0),
            value: 5,
            groupValue: _selectedVal,
            onChanged: (int newValue) {
              setState(() {
                _selectedVal = newValue;
              });
            },
            itemOrder: _LinePainter.MIDDLE_ITEM,
          ),
          LabeledRadio(
            label: 'Strongly Agree',
            padding: const EdgeInsets.symmetric(horizontal: 5.0),
            value: 6,
            groupValue: _selectedVal,
            onChanged: (int newValue) {
              setState(() {
                _selectedVal = newValue;
              });
            },
            itemOrder: _LinePainter.LAST_ITEM,
          ),
        ],
      ),
    );
  }
}

class _LinePainter extends CustomPainter {
  static const FIRST_ITEM = -1;
  static const MIDDLE_ITEM = 0;
  static const LAST_ITEM = 1;
  
  int buttonType;
  
  _LinePainter(this.buttonType);
  
  @override
  void paint(Canvas canvas, Size size) {
    final p = Paint()
      ..color = Colors.black
      ..strokeWidth = 2;
    if (buttonType == MIDDLE_ITEM || buttonType == LAST_ITEM) {
      canvas.drawLine(Offset(29, 0), Offset(29, (size.height / 2) - 9), p);
    }
    if (buttonType == FIRST_ITEM || buttonType == MIDDLE_ITEM) {
    canvas.drawLine(
        Offset(29, (size.height / 2) + 9), Offset(29, size.height), p);
      
    }
  }

  @override
  bool shouldRepaint(_LinePainter oldDelegate) => false;
}