Working with checkboxes in Flutter

main.dart

class TODOState extends State<TODO> {

  final List<Task> tasks = [];

  void onTaskCreated(String name) {
    setState(() {
      tasks.add(Task(name));
    });
  }
  
  // A new callback function to toggle task's completion
  void onTaskToggled(Task task) {
    setState(() {
      task.setCompleted(!task.isCompleted());
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'TODO app',
      initialRoute: '/',
      routes: {
        // Passing the function as a callback
        '/': (context) => TODOList(tasks: tasks, onToggle: onTaskToggled),
        '/create': (context) => TODOCreate(onCreate: onTaskCreated,),
      },
    );
  }
}

class TODOList extends StatelessWidget {

  final List<Task> tasks;
  final onToggle;

  TODOList({@required this.tasks, @required this.onToggle});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('TODO app'),
      ),
      body: ListView.builder(
          itemCount: tasks.length,
          itemBuilder: (context, index) {
            // Changed ListTile to CheckboxListTile to have
            // the checkbox capability
            return CheckboxListTile(
              title: Text(tasks[index].getName()),
              // Passing a value and a callback for the checkbox
              value: tasks[index].isCompleted(),
              // The _ in the argument list is there because onChanged expects it
              // But we are not using it
              onChanged: (_) => onToggle(tasks[index]),
            );
          }),
      floatingActionButton: FloatingActionButton(
        onPressed: () => Navigator.pushNamed(context, '/create'),
        child: Icon(Icons.add)
      ),
    );
  }
}