細節:這是一個閃存卡遊戲,每張卡都有問題和答案。 QuizCard是一類具有getQuestion(),getAnswer(),setQuestion(),setAnswer()和兩個字符串實例作爲問答的函數的類。參數化的構造函數需要兩個字符串,第一個作爲問題,第二個作爲答案。
我將問題和答案保存在文本文件中,問題和答案由「/」分隔。所有新問題都從新的一行開始。
例如 - >什麼是印度首都/新德里
泰姬陵在哪裏?/阿格拉
其餘的代碼可以很容易地理解。
爪哇:在Flash卡遊戲中點擊JButton時拋出的NullPointerException異常
問題:單擊「nextButton」時,會拋出NullPointerException,並且不會更改「nextButton」上的文本。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
public class QuizCardPlayer
{
private JFrame frame;
private JTextArea display;
private boolean isAnswer = true;
private JButton nextButton;
private ArrayList<QuizCard> cardList;
private int currentCardIndex;
public static void main(String[] args)
{
QuizCardPlayer player = new QuizCardPlayer();
player.go();
}
public void go()
{
frame = new JFrame("Quiz Card Player");
display = new JTextArea(6,20);
JPanel mainPanel = new JPanel();
Font bigFont = new Font("serif", Font.BOLD, 24);
display.setFont(bigFont);
JScrollPane scroller = new JScrollPane(display);
scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
display.setText("Lets Start!");
JButton nextButton = new JButton("Show Question");
mainPanel.add(scroller);
mainPanel.add(nextButton);
nextButton.addActionListener(new NextButtonListener());
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
JMenuItem loadMenuItem = new JMenuItem("Load card set");
loadMenuItem.addActionListener(new LoadMenuListener());
fileMenu.add(loadMenuItem);
menuBar.add(fileMenu);
frame.setJMenuBar(menuBar);
frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
frame.setVisible(true);
frame.setSize(300,300);
}
public class NextButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
System.out.print("Called!!");
if(isAnswer)
{
nextButton.setText("Show Answer");
if(currentCardIndex < cardList.size())
{
display.setText(cardList.get(currentCardIndex).getQuestion());
isAnswer = false;
}
else
{
display.setText("That was last Card.");
nextButton.setEnabled(false);
}
}
else
{
nextButton.setText("Next Card");
display.setText(cardList.get(currentCardIndex).getAnswer());
isAnswer = true;
currentCardIndex++;
}
}
}
public class LoadMenuListener implements ActionListener
{
public void actionPerformed(ActionEvent ev)
{
JFileChooser openFile = new JFileChooser();
openFile.showOpenDialog(frame);
loadFile(openFile.getSelectedFile());
}
}
public void loadFile(File loadFile)
{
try
{
BufferedReader reader = new BufferedReader(new FileReader(loadFile));
String line="";
cardList = new ArrayList<QuizCard>();
while((line = reader.readLine()) != null)
{
String[] result = line.split("/");
QuizCard card = new QuizCard(result[0] , result[1]);
cardList.add(card);
currentCardIndex=0;
}
reader.close();
}
catch(IOException ex)
{
ex.printStackTrace();
}
}
}
我是新手在Java有一個月的經驗,任何建議是最受歡迎的。
感謝調試,但我應該怎麼做才能解決這個問題? – 2015-04-04 13:50:18
@PalkeshJain:請參閱編輯,OP。我希望這會排序thingies :-) – 2015-04-04 14:03:13
謝謝,問題解決了。 :) – 2015-04-04 15:18:14