我试图用Java进行测验，但是我无法从测试人员类中访问数组列表数据，因此我的问题文本没有显示出来。我有三节课;测试器，测验界面和测验设置。我已经玩了一段时间了，我很确定我开始让事情变得更糟，所以我想我会在这里发帖。
问题被添加到Tester文件的数组列表中，但我似乎无法在此方法的设置类中访问它：
public void setQuestion(int randIndex) {
qi.getQuText().setText(getQuestionList().get(randIndex).getQuestionText());
}
预期输出是从数组列表中随机提出问题并显示问题文本，但不会显示任何内容，而是空白。
我对Java和编程很新，所以欢迎任何详细的答案！提前谢谢。
import java.util.ArrayList;
public class QuizTester {
private static ArrayList<Question> questions; //declares arrayList to holds the questions
public static void main(String[] args) {
QuizSetUp theQuiz = new QuizSetUp();
questions = new ArrayList<Question>(); //constructor
questions.add(new FillInBlank("____________ is the ability of an object to take many forms.", "Polymorphism"));
questions.add(new FillInBlank("The process where one object acquires the properties of another is called __________", "inheritance"));
questions.add(new FillInBlank("The ___________ keyword is used by classes to inherit from interfaces", "implements"));
questions.add(new MultipleChoice("Which programming technique can be used to prevent code and data from being randomly accessed by other code defined outside the class?",
"Polymorphism", "Encapsulation", "Inheritance", "Construction", "Encapsulation"));
theQuiz.pickQuestion();
}
public ArrayList<Question> getQuestionList() {
return this.questions;
}
}
//////////////////////// quiz设置档案。
public class QuizSetUp {
private QuizInterface qi;
private QuizTester test;
//private ArrayList<Question> questions; //declares arrayList to holds the questions
private int counter = 1;
Random random;
int randIndex;
public QuizSetUp() {
setInterface();
//questions = new ArrayList<Question>(); //constructor
}
private enum QuAnswer { CORRECT,INCORRECT }
public void setInterface() {
qi = new QuizInterface();
test = new QuizTester();
//add action listeners to each of the buttons
ActionListener cl = new ClickListener();
qi.getNextBtn().addActionListener(cl);
qi.getStartQuizBtn().addActionListener(cl);
//allows users to press enter to start quiz rather than having to click quiz button
KeyListener ent = new KeyBoardListener();
qi.getUName().addKeyListener(ent);
qi.getUPassword().addKeyListener(ent);
}
public void pickQuestion() {
randQuestion();
setQuestion(randIndex);
//setAnswer("A", randIndex);
//setAnswer("B", randIndex);
//setAnswer("C", randIndex);
//setAnswer("D", randIndex);
//setCorrectAnswer(randIndex);
//qi.resetTimer();
}
public void setQuestion(int randIndex) {
qi.getQuText().setText(getQuestionList().get(randIndex).getQuestionText());
}
public void setNextQuestion() {
//qi.getTimer().cancel();
//qi.cancelInterval();
if (counter < 5) { //users must answer five questions to complete quiz
pickQuestion();
} else {
//JOptionPane.showMessageDialog(qi.getPanels(), "End of quiz");
//switch to end panel to show results of quiz
}
}
public int randQuestion() {
random = new Random();
randIndex = random.nextInt(questions.size());
return randIndex;
}
//inner listener class for buttons
private class ClickListener implements ActionListener {
public void actionPerformed(ActionEvent evt) {
if (evt.getSource() == qi.getStartQuizBtn()) {
qi.setEnteredName(qi.getUName().getText());
qi.setEnteredPass(qi.getUPassword().getPassword());
validateInput();
} else if (evt.getSource() == qi.getNextBtn()) {
counter++;
if (counter == 5) {
qi.getNextBtn().setText("Finish Quiz"); //changes next button text on final question
}
if (counter < 6) {
qi.getQuProgress().setText(counter + " of 5");
} else {
//shuffle to end panel
}
}
}
}
//inner listener class for key presses
private class KeyBoardListener implements KeyListener {
public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == KeyEvent.VK_ENTER) {
qi.setEnteredName(qi.getUName().getText());
qi.setEnteredPass(qi.getUPassword().getPassword());
validateInput();
}
}
@Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}
@Override
public void keyTyped(KeyEvent e) {
// TODO Auto-generated method stub
}
}
//method to validate input by user to log in
public void validateInput() {
//presence check on username
if (qi.getEnteredName().length() > 0) {
//presence check on password
if (qi.getEnteredPass().length > 0) {
//ensures password is at least 6 char long
if(qi.getEnteredPass().length > 5) {
qi.getCards().next(qi.getPanels()); //getPanels() == cardPanel
} else {
JOptionPane.showMessageDialog(null,
"Your password must be at least six characters long.",
"Password Violation", JOptionPane.WARNING_MESSAGE);
}
} else {
JOptionPane.showMessageDialog(null,
"Your did not enter a password.",
"Password Violation", JOptionPane.WARNING_MESSAGE);
}
} else {
JOptionPane.showMessageDialog(null,
"You did not enter a username. Please try again.",
"Username Violation", JOptionPane.WARNING_MESSAGE);
}
}
}
答案 0 :(得分：1)
经过一些改动，我能够让你的代码运行起来。但我必须警告你，有一些变化：
QuizTester现在只有main方法来启动该程序。它将初始化并填充列表中的问题，然后将其传递给QuizSetUp实例Question课程，因此我将其缩减为ArrayList<String>（只是为了确保问题可以通过）QuizInterface课程，所以我帮助自己完成了一个小实现，只需在设置新问题时打印出问题QuizInterface （小助手类）
public class QuizInterface {
private String text;
public QuizInterface() {
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
System.out.println("question text = "+this.text); // this is just to make sure it worked
}
}
QuizSetUp （严重减少）
public class QuizSetUp {
private QuizInterface qi;
private ArrayList<String> questions; // uncommented, it's needed now
private int counter = 1;
Random random;
int randIndex;
// I chose to pass the list with the constructor but the setQuestions() will do as well
public QuizSetUp(ArrayList<String> questions) {
this.questions = questions;
setInterface();
}
// NEW method – but it's not needed
public ArrayList<String> getQuestions() {
return questions;
}
// NEW method – but it's not needed
public void setQuestions(ArrayList<String> questions) {
this.questions = questions;
}
private enum QuAnswer {
CORRECT, INCORRECT
}
public void setInterface() {
qi = new QuizInterface();
// test = new QuizTester(); // this is no longer needed since QuizTester is only used to start the program
}
public void pickQuestion() {
randQuestion();
setQuestion(); // randIndex is already a global variable in this class, no need to pass with the method call
}
public void setQuestion() {
// QuizInterface has a new method now called "setText()"
// so here we access the list "questions" (it is already initialized, because we pass it to this class when constructing it)
// this.randIndex is global, so we can use it directly in this method as an index to the questions list (as you already did it)
qi.setText(this.questions.get(this.randIndex));
}
public void setNextQuestion() {
//qi.getTimer().cancel();
//qi.cancelInterval();
if (counter < 5) { //users must answer five questions to complete quiz
pickQuestion();
} else {
//JOptionPane.showMessageDialog(qi.getPanels(), "End of quiz");
//switch to end panel to show results of quiz
}
}
public int randQuestion() {
random = new Random();
randIndex = random.nextInt(questions.size());
return randIndex;
}
// .... the rest I left out here because it is not needed for this little test
}
QuizTester （只需要main方法）
public class QuizTester {
public static void main(String[] args) {
ArrayList<String> questions = new ArrayList<>(); //as you can see I replaced the List with a list of Strings (because I didn't have your Question class)
// so these are only strings...
questions.add("____________ is the ability of an object to take many forms.");
questions.add("The process where one object acquires the properties of another is called __________");
questions.add("The ___________ keyword is used by classes to inherit from interfaces");
questions.add("Which programming technique can be used to prevent code and data from being randomly accessed by other code defined outside the class?");
// here I create the QuizSetUp instance and pass the list right with the constructor
QuizSetUp theQuiz = new QuizSetUp(questions);
// if everything works out, calling this method
// should pick a new question, set it to the QuizInterface
// and the QuizInterface (the helper version I made) will print it out
theQuiz.pickQuestion();
}
}
这三个类可以按原样编译，当我运行程序时，我得到了这个输出
question text = The ___________ keyword is used by classes to inherit from interfaces
我知道这与你所拥有的有很大不同，我所做的唯一大更改是将新创建的问题列表直接传递给QuizSetUp实例 - 所以不能访问任何静态列表。
答案 1 :(得分：0)
看看这一行：
qi.getQuText().setText(getQuestionList().get(randIndex).getQuestionText());
getQuestionList()在哪里实施？它看起来像一个方法调用，除了QuizSetUp没有声明getQuestionList()方法。它属于不同的类别。
结论：您在问题中向我们展示的代码甚至无法编译。
我应该指出（QuezSetup）这种风格非常糟糕，容易造成混淆。
private static ArrayList<Question> questions;
public ArrayList<Question> getQuestionList() {
return this.questions;
}
虽然this.questions 看起来就像它指的是一个实例变量，但它实际上是指一个静态变量。 this具有误导性。