dart hello world

main.dart

import 'package:flutter/material.dart';
import 'dart:math';
import 'dart:async';

void main() {
  runApp(CalendarApp());
}

class CalendarApp extends StatelessWidget {
  Widget build(BuildContext context) {
    const todos = [
      "Clean gutters",
      "Grocery shopping",
      "Grocery shopping Grocery shopping Grocery shopping Grocery shopping Grocery shopping Grocery shopping Grocery shopping",
      "Oil change",
      "Clip cats claws",
      "Go to the gym",
    ];
    return MaterialApp(
      home: Scaffold(
        body: Column(
          children: <Widget>[
            TodoRotator(Duration(seconds: 3), 2, todos),
          ],
        ),
      ),
    );
  }
}

class TodoRotator extends StatefulWidget {
  
  final Duration rotateInterval;
  final int perPage;
  final List<String> allItems;
  
  TodoRotator(this.rotateInterval, this.perPage, this.allItems);
  
  @override
  _TodoRotatorState createState() => _TodoRotatorState(rotateInterval, perPage, allItems, 0);
}

class _TodoRotatorState extends State<TodoRotator> {
  
  final Duration rotateInterval;
  final int perPage;
  final List<String> allItems;
  int startOffset;
  late Timer timer;
  
  _TodoRotatorState(this.rotateInterval, this.perPage, this.allItems, this.startOffset);
  
  void nextPage() {
    setState(() {
        startOffset += perPage;
        if (startOffset >= allItems.length) {
          startOffset = 0;
        }
    });
  }
  
  @override
  void initState() {
    super.initState();
    timer = Timer.periodic(rotateInterval, (Timer t) => nextPage());
  }
  
  @override
  Widget build(BuildContext context) {
    final endOffset = min(startOffset + perPage, allItems.length);
    return TodoWidget(allItems.sublist(startOffset, endOffset));
  }
}

class TodoWidget extends StatelessWidget {

  final List<String> todos;

  TodoWidget(this.todos);

  Widget build(BuildContext context) {
    List<Widget> children = [
      Text("TODO",
          style: const TextStyle(fontSize: 20, fontWeight: FontWeight.bold))
    ];
    for (var i = 0; i < todos.length; i++) {
      children.add(
          Text("${i + 1}) ${todos[i]}", style: const TextStyle(fontSize: 15)));
    }
    return  Column(
        mainAxisAlignment: MainAxisAlignment.start,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: children,
    );
  }
}