Flutter layout:如何垂直扩展小部件

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Vertical Expansion'),
        ),
        body: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Expanded(
              child: Container(
                color: Colors.red,
                child: Text('Widget 1'),
              ),
            ),
            Expanded(
              child: Container(
                color: Colors.blue,
                child: Text('Widget 2'),
              ),
            ),
            Expanded(
              child: Container(
                color: Colors.green,
                child: Text('Widget 3'),
              ),
            ),
          ],
        ),
      ),
    );
  }
}