如何让我的 elevatedButton 小部件调用 Flutter 中的函数？

Question

我试图让我的提升按钮响应我在另一个小部件中创建的功能，但在它递增时遇到问题。有人可以协助并告诉我我做错了什么吗？我将所有内容都放在 answer.dart 文件中，以便它调用 answerQuestion 函数

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


// Main that runs the MyApp class
void main() {
  runApp(MyApp());
}

// Stateful MyApp
class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _MyAppState();
  }
}

// MyAppState  Generic State
class _MyAppState extends State<MyApp> {
  var _questionIndex = 0;
  // ignore: unused_local_variable
  void _answerQuestion() {
    setState(() {
      _questionIndex = _questionIndex + 1;
    });
    print(_questionIndex);
  }

  @override
  Widget build(BuildContext context) {
    // FIRST METHOD

    // QUESTION VARIABLE
    // ignore: unused_local_variable
    var questions = [
      'What\'s your favorite food?',
      'What\'s your favorite color?'
    ];

    // RETURNS MATERIAL APP FOR FLUTTER
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('My First App'),
        ),
        body: Column(
          children: [
           Question(
            questions[_questionIndex],
          ),
          Answer(_answerQuestion),
          Answer(_answerQuestion),
          Answer(_answerQuestion),
         ],
        ),
      ),
    );
  }
}

回答.dart

import 'package:flutter/material.dart';
 
class Answer extends StatelessWidget {
  final Function selectHandler;
 
 Answer({Key? key, required this.selectHandler}) : super(key: key);
  
  @override
  Widget build(BuildContext context) {
    return Container(
      width: double.infinity,
      child: ElevatedButton(
            style: ElevatedButton.styleFrom(
            primary: Color.fromARGB(255, 9, 131, 232),
          ),
          child: Text('Answer'),
          
          onPressed: () {
            selectHandler;
          },
          ),
    );
  }
}

问题.dart

import 'package:flutter/material.dart';
 
class Question extends StatelessWidget {
  final String questionText;
 
  Question(this.questionText);
 
  @override
  Widget build(BuildContext context) {
    return Container(
      width: double.infinity,
      margin: EdgeInsets.all(10.0),
      child: Text(
        questionText,
        style: TextStyle(fontSize: 28),
        textAlign: TextAlign.center,
      ),
    );
  }
}

Answer 1

和之前的回答一样 进行这些更改。

onPressed: selectHandler,

和

Answer(selectHandler: _answerQuestion),

Answer 2

你可以做

 onPressed: () {
   selectHandler(); //missing ()

或者做

 onPressed: selectHandler,

Answer 小部件上的另一件事，您正在使用命名参数，喜欢

 Answer(selectHandler: _answerQuestion),