Flutter Layout Row / Column - share width, expand height

Have a look at IntrinsicHeight; wrapping the root Row should provide the effect you're looking for:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(title: Text('Rows & Columns')),
        body: RowsAndColumns(),
      ),
    );
  }
}

class RowsAndColumns extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.only(top: 100.0),
      child: IntrinsicHeight(
        child: Row(crossAxisAlignment: CrossAxisAlignment.stretch, children: [
          Expanded(
            child: Column(children: [
              Container(height: 120.0, color: Colors.yellow),
              Container(height: 100.0, color: Colors.cyan),
            ]),
          ),
          Expanded(child: Container(color: Colors.amber)),
        ]),
      ),
    );
  }
}

Adjusting the heights in the containers in the column cause the container on the right to resize to match:

https://gist.github.com/mjohnsullivan/c5b661d7b3b4ca00599e8ef87ff6ac61

I'm new to flutter. Please correct me if I'm doing something wrong here. I think It can also be achieved using setState((){}) without using IntrinsicHeight.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}`enter code here`

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return MyAppState();
  }
}

class MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    double h1 = 100;
    double h2 = 200;
    double h3;
    setState(() {
      h3 = h1 + h2;
    });
    return MaterialApp(
      home: Scaffold(
        body: SafeArea(
          child: Padding(
            padding: const EdgeInsets.only(top: 100.0),
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Expanded(
                  child: Column(
                    children: [
                      Container(
                        color: Colors.green,
                        height: h1,
                      ),
                      Container(
                        color: Colors.orange,
                        height: h2,
                      )
                    ],
                  ),
                ),
                Expanded(
                  child: Container(
                    color: Colors.yellow,
                    height: h3,
                  ),
                )
              ],
            ),
          ),
        ),
      ),
    );
  }
}

Find image here

Code can also be found here: https://gist.github.com/Amrit0786/9d228017c2df6cf277fbbaa4a6b20e83