Expanded 03

03_expanded.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false, 
      home: ExpandedExample03(),
    );
  }
}

class ExpandedExample03 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        height: 100,
        child: Row(
          children: [
            Container(
              width: 100,
              color: Colors.red,
            ),
            Expanded(
              child: Container(
                color: Colors.blue[900],
              ),
            ),
          ],
        ),
      ),
    );
  }
}