yadu-sayone

@override
Widget build(BuildContext context) {
  return new Scaffold(
    backgroundColor: Theme.of(context).primaryColor,
    body: SafeArea(
      child: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          children: <Widget>[
            Expanded(

yadu-sayone

import 'package:flutter/material.dart';

class UnaryOperatorButton extends StatelessWidget {

  UnaryOperatorButton({this.text,this.onPressed});

  final String text;
  final Function onPressed;

  @override

yadu-sayone

import 'package:flutter/material.dart';

class BinaryOperatorButton extends StatelessWidget {
  BinaryOperatorButton({this.onPressed,this.text});

  final text;
  final Function onPressed;

  @override
  Widget build(BuildContext context) {

yadu-sayone

import 'package:flutter/material.dart';

class ZeroButton extends StatelessWidget {
  ZeroButton({this.onPressed});

  final Function onPressed;
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(5.0),

yadu-sayone

import 'package:flutter/material.dart';

class NumberButton extends StatelessWidget {
 NumberButton({this.text,this.onPressed});

 final String text;
 final Function onPressed;

 @override
 Widget build(BuildContext context) {

yadu-sayone

const double _radiansPerDegree = Math.pi / 180;
final double _startAngle = -90.0 * _radiansPerDegree;
double _itemSpacing = 360.0 / 5.0;
double _calculateItemAngle(int index) {
 return _startAngle + index * _itemSpacing * _radiansPerDegree;
}

yadu-sayone

class _CircularLayoutDelegate extends MultiChildLayoutDelegate {
  static const String actionButton = 'BUTTON';
  Offset center;
  final int itemCount;
  final double radius;

  _CircularLayoutDelegate({
    @required this.itemCount,
    @required this.radius,
  });

yadu-sayone

for (int i = 0; i < 5; i++) {
  products.add( LayoutId(
    id: ‘BUTTON$i’,
    child: item,
  ));
}

yadu-sayone

CustomMultiChildLayout(
  delegate: _CircularLayoutDelegate(
    itemCount: 5,
    Radius: 150.0,
  ),
  children: products,
)