如何在Card Widget中设置两种背景颜色？

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Card Widget Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Card Widget Example'),
      ),
      body: Center(
        child: Card(
          child: Container(
            decoration: BoxDecoration(
              gradient: LinearGradient(
                begin: Alignment.topLeft,
                end: Alignment.bottomRight,
                colors: [
                  Colors.blue,
                  Colors.green,
                ],
              ),
            ),
            child: Padding(
              padding: EdgeInsets.all(16.0),
              child: Text(
                'This is a Card Widget',
                style: TextStyle(
                  color: Colors.white,
                  fontSize: 20.0,
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}