main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: Home(),
    );
  }
}

class Home extends StatefulWidget {
  const Home({
    Key? key,
  }) : super(key: key);

  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  final _selected = <MyClass>[];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Material App Bar'),
      ),
      body: Center(
        child: SizedBox(
          width: 500,
          child: GridView(
            gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 2,
            ),
            children: [
              for (var item in _list) _build(item),
            ],
          ),
        ),
      ),
    );
  }

  Widget _build(MyClass item) {
    final isSelected = _selected.contains(item);
    return Container(
      height: 100,
      width: 100,
      color: isSelected ? Colors.blue : Colors.green,
      child: InkWell(
        onTap: () {
          setState(() {
            if (!isSelected) {
              _selected.add(item);
            } else {
              _selected.remove(item);
            }
          });
        },
        child: Padding(
          padding: const EdgeInsets.all(8.0),
          child: Image.network(
            item.image,
          ),
        ),
      ),
    );
  }
}

class MyClass {
  final String image;
  MyClass(this.image);
}

final List<MyClass> _list = [
  MyClass(
    'https://images.pexels.com/photos/7363245/pexels-photo-7363245.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260',
  ),
  MyClass(
    'https://images.pexels.com/photos/7558430/pexels-photo-7558430.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260',
  ),
  MyClass(
    'https://images.pexels.com/photos/1640777/pexels-photo-1640777.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=750&w=1260',
  ),
];