import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

const kSwatchSize = 36.0;

void main() {
  runApp(new MaterialApp(
      home: new Scaffold(
    body: new Stack(children: [new Positioned(left:200.0,top:200.0,
      child: new SizedBox(width: 600.0,height: 300.0,
          child: new GridView.count(
            crossAxisCount: 6,
            children: _getColorMenuTileItems(),
          )),
    ), ]),
  )));
}

List<PopupMenuItem<Color>> _getColorMenuTileItems() {
  final colors = Colors.primaries.map((c) => c).toList();
  colors.addAll([Colors.black, Colors.grey, Colors.white]);
  return colors.map((c) {
    return new PopupMenuItem<Color>(
      value: c,
      child: new GridTile(
        child: new Container(
          width: kSwatchSize,
          height: kSwatchSize,
          color: c,
        ) ),
    );
  }).toList();
}