Flutter - Making a gradeint app body background using decoration

main.dart

import 'package:flutter/material.dart';

//
// Created by Braulio Cassule
// 30 December 2017
//

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

class MyApp extends StatelessWidget {

  ///
  /// * I would suggest heading on to
  /// * https://material.io/guidelines/style/color.html#color-color-palette
  /// * to choose your colors 
  ///
  
  Color gradientStart = Colors.deepPurple[700]; //Change start gradient color here
  Color gradientEnd = Colors.purple[500]; //Change end gradient color here

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: new Text('Gradient Decoration'),
        ),
        body: new Container(
          decoration: new BoxDecoration(
            gradient: new LinearGradient(colors: [gradientStart, gradientEnd],
                begin: const FractionalOffset(0.5, 0.0),
                end: const FractionalOffset(0.0, 0.5),
                stops: [0.0,1.0],
                tileMode: TileMode.clamp
            ),
          ),
        ),
      ),
    );
  }
}

The Result should look something like this