Flutter Layout Row / Column - share width, expand height

Since IntrinsicHeight is considered relatively expensive, it's better to avoid it. You can use Table with verticalAlignment: TableCellVerticalAlignment.fill in the largest TableCell.

Please note that if you use .fill in all cells, the TableRow will have zero height.

  Table(children: [
    TableRow(children: [
      Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Container(
            alignment: Alignment.center,
            color: Colors.blue,
            child: Text('Widget 1'),
          ),
          Container(
            alignment: Alignment.center,
            color: Colors.green,
            child: Text('Widget 2'),
          ),
        ],
      ),
      TableCell(
          verticalAlignment: TableCellVerticalAlignment.fill,
          child: Container(
            alignment: Alignment.center,
            color: Colors.orange,
            child: Text('Widget 3'),
          )),
    ]),
  ]),

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 think that you can set the height of the row instead, then you only must to set the height of you column containers, and with the crossAxisAlignment: CrossAxisAlignment.stretch the second row will be expand occupying his parent height:

SizedBox(
 height: 100,
 child: Row(
 crossAxisAlignment: CrossAxisAlignment.stretch,
 children: [
  Expanded(
    child: Column(
      children: [
        Expanded( //If you dont have the height you can expanded with flex
          flex: 1,
          child: Container(
            height: 50,
            color: Colors.blue,
          ),
        ),
        Expanded(
          flex: 1,
          child: Container(
            height: 50,
            color: Colors.red,
          ),
        )
      ],
    ),
  ),
  Expanded(
    child: Container(
      color: Colors.yellow,
    ),
   )
  ],
 ),
),