GridView.extent

extent.dart

import 'package:flutter/material.dart';

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

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

class GridViewExtentWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
       appBar: AppBar(
         title: Text('GridView.extend'),
         centerTitle: true,
       ),
      body: GridViewWidgetDemo(),
    );
  }
}

class GridViewWidgetDemo extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GridView.extent(
      maxCrossAxisExtent: 200,
      children: [
        Item1(), Item2(), Item3(), Item4(),
      ],
    );
  }
}

class Item1 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.pinkAccent,
    );
  }
}

class Item2 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.red,
    );
  }
}

class Item3 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.blue[900],
    );
  }
}

class Item4 extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.orange,
    );
  }
}