Flutter:不能将类型为lib1 :: Object的值分配给类型为lib2 :: Object的变量 [英] Flutter: A value of type lib1::Object can't be assigned to a variable of type lib2::Object

问题描述

在尝试编译此代码时:

import 'package:flutter/material.dart';
import 'package:startup_namer/misc/Constants.dart';
import 'package:startup_namer/ui/question_text.dart';
import '../utils/question.dart';
import '../utils/quiz.dart';
import '../ui/answer_button.dart';
import '../ui/correct_wrong_overlay.dart';

class QuizPage extends StatefulWidget {
    @override
    State createState() => new QuizPageState();
}

//States are mutable
class QuizPageState extends State<QuizPage> {

    static List<Question> quizQuestions = [
        new Question("5 * 5 = 25", true),
        new Question("4 + 2 = 6", true),
        new Question("4 + 2 = 7", false),
        new Question("Computers don't use energy", false),
        new Question("B is after A in the alphabet", false),
    ];

    Question currentQuestion;
    Quiz quiz = new Quiz(quizQuestions);

    String questionText;
    int questionNumber;
    bool isCorrect, overlayShouldBeVisible = false;


    @override
    void initState() {
        super.initState();
        this.currentQuestion = this.quiz.nextQuestion;
        this.questionText = this.currentQuestion.aQuestion;
        this.questionNumber = this.quiz.questionNumber;
    }

    @override
    Widget build(BuildContext context) {
        return new Stack( 
            fit: StackFit.expand,
            children: <Widget>[
                //Container for tons of stuff (Main page essentially)
                new Column(
                    children: <Widget>[
                        new AnswerButton(true,  () => testMe(true)),
                        new QuestionText(this.questionText, this.questionNumber),
                        new AnswerButton(false, () => testMe(false)),
                    ], //<Widget>[]
                ), //Column
                (this.overlayShouldBeVisible) ? new CorrectWrongOverlay(true) : new Container()
            ] //<Widget>[]
        ); //Stack
    }
}

void testMe(bool isTrue){
    if(isTrue){
        print("it is true, huzzah!");
    } else {
        print("it is false, :(");
    }
}

我收到此错误:

Error: A value of type 'dart.core::List<#lib1::Question>' can't be assigned to a variable of type 'dart.core::List<#lib2::Question>'.

我正在遵循本教程系列，并已根据其存储库检查了代码，但我无法查看导致此问题的原因.

I am following this tutorial series and have checked the code against their Repository but am unable to see what is causing this problem.

如果没有其他模棱两可的 Question 类与此冲突，为什么我会看到此强制转换错误?

Why would I be seeing this casting error if there are no other ambiguous Question classes that conflict with it?

推荐答案

事实证明，问题与进口申报的方式有关.

It turns out the issue had to do with how the imports were being declared up top.

我在其他地方没有看到此问题，因此我将在此处回答问题.从这些更新我的进口商品:

I have not seen this mentioned elsewhere so I will answer the question here. Updating my imports from these:

import '../utils/question.dart';
import '../utils/quiz.dart';
import '../ui/answer_button.dart';
import '../ui/correct_wrong_overlay.dart';

这些

import 'package:startup_namer/utils/question.dart';
import 'package:startup_namer/utils/quiz.dart';
import 'package:startup_namer/ui/answer_button.dart';
import 'package:startup_namer/ui/correct_wrong_overlay.dart';

在我使用完整软件包声明而不是简写版本的地方，似乎可以解决此问题.

Where I am using the full package declaration as opposed to the shorthand version seems to resolve the issue.

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