如何将线性渐变赋予我的整个flutter应用程序？

import 'package:flutter/painting.dart';

MaterialApp(
  theme: ThemeData(
    // 定义线性渐变
    primaryColor: Colors.white,
    appBarTheme: AppBarTheme(
      // 使用线性渐变作为AppBar的背景色
      color: LinearGradient(
        begin: Alignment.topLeft,
        end: Alignment.bottomRight,
        colors: [Colors.blue, Colors.green],
      ),
    ),
  ),
  home: MyHomePage(),
);

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        decoration: BoxDecoration(
          // 使用线性渐变作为容器的背景色
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: [Colors.blue, Colors.green],
          ),
        ),
        child: Center(
          child: Text(
            'Hello, Flutter!',
            style: TextStyle(
              fontSize: 24,
              color: Colors.white,
            ),
          ),
        ),
      ),
    );
  }
}