Flutter: Why renaming "MyApp" symbol to "Timer" in visual studio code generates errors

Question

I'm implementing simple timer app using flutter code but changing name creating 4 errors, error messages are as follow:

1. Unused import: 'dart:async'. Try removing the import directive.
2. The method 'cancel' isn't defined for the type 'Timer'. Try correcting the name to the name of an existing method, or defining a method named 'cancel'.
3. The method 'periodic' isn't defined for the type 'Timer'. Try correcting the name to the name of an existing method, or defining a method named 'periodic'.
4. The method 'cancel' isn't defined for the type 'Timer'. Try correcting the name to the name of an existing method, or defining a method named 'cancel'.

My code is bellow:

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

void main() => runApp(MyApp()); //change MyApp to Timer

class MyApp extends StatelessWidget { //change MyApp to Timer
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 10;
  Timer _timer;

  void _startTimer() {
    _counter = 10;
    if (_timer != null) {
      _timer.cancel();
    }
    _timer = Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        if (_counter > 0) {
          _counter--;
        } else {
          _timer.cancel();
        }
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Timer App"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            (_counter > 0)
                ? Text("")
                : Text(
                    "DONE!",
                    style: TextStyle(
                      color: Colors.green,
                      fontWeight: FontWeight.bold,
                      fontSize: 48,
                    ),
                  ),
            Text(
              '$_counter',
              style: TextStyle(
                fontWeight: FontWeight.bold,
                fontSize: 48,
              ),
            ),
            RaisedButton(
              onPressed: () => _startTimer(),
              child: Text("Start 10 second count down"),
            ),
          ],
        ),
      ),
    );
  }
}

question from:https://stackoverflow.com/questions/65869999/flutter-why-renaming-myapp-symbol-to-timer-in-visual-studio-code-generates

Answer 1

In 'dart:async' already exists a class named "Timer". As you are importing this, you can't have two classes with the same name. Because it's an abstract class vs code wants you to override those methods.