The method isn't defined for the class - Flutter

Question

I'm new to flutter and have been trying to make a simple quiz app. I've encountered an error and I'm not sure what is wrong.

Error:

Compiler message:                                                       
lib/main.dart:37:17: Error: The method 'Answer' isn't defined for the class '_MyAppState'.
 - '_MyAppState' is from 'package:project2/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'Answer'.
                Answer(),                                               
                ^^^^^^                                                  
lib/main.dart:38:17: Error: The method 'Answer' isn't defined for the class '_MyAppState'.
 - '_MyAppState' is from 'package:project2/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'Answer'.
                Answer(),                                               
                ^^^^^^                                                  
lib/main.dart:39:17: Error: The method 'Answer' isn't defined for the class '_MyAppState'.
 - '_MyAppState' is from 'package:project2/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing method, or defining a method named 'Answer'.
                Answer()                                                
                ^^^^^^     

main.dart:

import 'package:flutter/material.dart';
import './questions.dart';
import './answer.dart';

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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _MyAppState();
  }
}

class _MyAppState extends State<MyApp> {
  var _questionIndex = 0;

  var _questions = ["Question 1?", "Question 2?", "Question 3?"];

  void _answerQuestion() {
    setState(() {
      _questionIndex = _questionIndex + 1;
    });

    print("You answered the question!");
  }

  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
            appBar: AppBar(
              title: Text("Quiz"),
            ),
            body: Column(
              children: <Widget>[
                Question(_questions[_questionIndex]),
                Answer(),
                Answer(),
                Answer()
              ],
            )));
  }
}

answer.dart:

import 'package:flutter/material.dart';

class Answer extends StatelessWidget {

  @override
  Widget build(BuildContext context) {
    return Container(
        width: double.infinity,
        color: Colors.blue,
        child: RaisedButton(child: Text("Answer 1"), onPressed: null));
  }
}

I have used the same class name and imported the right file into main.dart. I'm not sure what's wrong. Can someone please point it out to me. Thanks in advance!

Answer 1

I don't recommend writing imports by your self, when you have some widget or function that is not imported an error will be highlighted with indicating suggestions to fix that . here is an example :

• call your function or widget, here I have a widget to call :
  

• as you can see an error is highlighted suggesting to import

• click that then the widget is import correctly
  

this will prevent such errors for you in the future

Answer 2

I to had a similar issue. Even though my import statement is correct i had this issue.

Then i have did "flutter clean" and after "flutter run" it worked.

So, just clean the build using "flutter clean" and see. hope it works.

Answer 3

I'm unable to replicate the same error that you received without a complete minimal repro and steps to reproduce the behavior. In my testing, an error occurred when import 'answer.dart'; was manually added in main.dart and ran the app with hot reload. Since it was a hot reload and the import was manually added, it's likely that code changes weren't included, causing the issue. The app works fine after a restart, and the issue doesn't occur when you let the IDE auto-complete the import. 

With the current details, I'm unable to rule out any definite cause for your issue.

I'm running on Flutter stable channel version 1.22.0

Error I got:

════════ Exception caught by widgets library ═══════════════════════════════════════════════════════
The following _CompileTimeError was thrown building MyApp(dirty, state: _MyAppState#2340f):
Unimplemented handling of missing static target

The relevant error-causing widget was: 
  MyApp file:///Users/{USER}/Downloads/dev/flutter/sample60384439/lib/main.dart:5:23
When the exception was thrown, this was the stack: 
#0      StatefulElement.build (package:flutter/src/widgets/framework.dart:4744:28)
#1      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4627:15)
#2      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4800:11)
#3      Element.rebuild (package:flutter/src/widgets/framework.dart:4343:5)
#4      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2730:33)
...
════════════════════════════════════════════════════════════════════════════════════════════════════
Reloaded 2 of 530 libraries in 220ms.