import javax.swing.*;
import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Scanner;
import java.util.Random;
import java.awt.*;
import java.awt.event.*;
public class RPSGraphics implements ActionListener
{
int gamesWon = 0;
int gamesLost = 0;
int gamesTied = 0;
JPanel titlePanel, scorePanel, buttonPanel;
JLabel playerLabel, compLabel, playerScore, compScore, tieScore;
JButton rocketsButton, panthersButton, spartansButton, resetButton;
public JPanel createContentPane ()
{
JPanel totalGUI = new JPanel();
totalGUI.setLayout(null);
titlePanel = new JPanel();
titlePanel.setLayout(null);
titlePanel.setLocation(10, 0);
titlePanel.setSize(250, 30);
totalGUI.add(titlePanel);
playerLabel = new JLabel("You:");
playerLabel.setLocation(0, 0);
playerLabel.setSize(120, 30);
playerLabel.setHorizontalAlignment(0);
playerLabel.setForeground(Color.red);
titlePanel.add(playerLabel);
compLabel = new JLabel("Computer:");
compLabel.setLocation(130, 0);
compLabel.setSize(120, 30);
compLabel.setHorizontalAlignment(0);
compLabel.setForeground(Color.blue);
titlePanel.add(compLabel);
scorePanel = new JPanel();
scorePanel.setLayout(null);
scorePanel.setLocation(10, 40);
scorePanel.setSize(260, 30);
totalGUI.add(scorePanel);
playerScore = new JLabel(""+gamesWon);
playerScore.setLocation(0, 0);
playerScore.setSize(120, 30);
playerScore.setHorizontalAlignment(0);
scorePanel.add(playerScore);
compScore = new JLabel(""+gamesLost);
compScore.setLocation(130, 0);
compScore.setSize(120, 30);
compScore.setHorizontalAlignment(0);
scorePanel.add(compScore);
compScore = new JLabel(""+gamesTied);
compScore.setLocation(65, 0);
compScore.setSize(120, 30);
compScore.setHorizontalAlignment(0);
scorePanel.add(tieScore);
//BUTTONS
buttonPanel = new JPanel();
buttonPanel.setLayout(null);
buttonPanel.setLocation(10, 80);
buttonPanel.setSize(260, 70);
totalGUI.add(buttonPanel);
rocketsButton = new JButton("Rockets");
rocketsButton.setLocation(0, 0);
rocketsButton.setSize(120, 30);
rocketsButton.addActionListener(this);
buttonPanel.add(rocketsButton);
panthersButton = new JButton("Panthers");
panthersButton.setLocation(130, 0);
panthersButton.setSize(120, 30);
panthersButton.addActionListener(this);
buttonPanel.add(panthersButton);
spartansButton = new JButton("Spartans");
spartansButton.setLocation(65, 0);
spartansButton.setSize(120, 30);
spartansButton.addActionListener(this);
buttonPanel.add(spartansButton);
//resetButton = new JButton("New Game");
//resetButton.setLocation(0, 40);
//resetButton.setSize(250, 30);
//resetButton.addActionListener(this);
//buttonPanel.add(resetButton);
totalGUI.setOpaque(true);
return totalGUI;
}
public void actionPerformed(ActionEvent e)
{
Scanner scan = new Scanner(System.in);
Random generator = new Random();
int gamesPlayed = 0;
//1 = Rockets
//2 = Panthers
//3 = Spartans
while (gamesPlayed < 5)
{
int compChoice = generator.nextInt(3) + 1;
if(e.getSource() == rocketsButton && compChoice == 3) //player: Rock, comp: Scissors
{
gamesWon = gamesWon + 1;
playerScore.setText(""+ gamesWon);
gamesPlayed++;
}
else if(e.getSource() == rocketsButton && compChoice == 2) //player:Rock, comp: Paper
{
gamesLost = gamesLost + 1;
compScore.setText(""+gamesLost);
gamesPlayed++;
}
else if(e.getSource() == rocketsButton && compChoice == 1) //player:Rock, comp: Rock
{
gamesTied = gamesTied + 1;
tieScore.setText(""+gamesTied);
gamesPlayed++;
}
else if(e.getSource() == panthersButton && compChoice == 3) //player: Paper, comp: Scissors
{
gamesLost = gamesLost + 1;
compScore.setText(""+gamesLost);
}
else if(e.getSource() == panthersButton && compChoice == 2) //player: Paper, comp: Paper
{
gamesTied = gamesTied + 1;
tieScore.setText(""+gamesTied);
gamesPlayed++;
}
else if(e.getSource() == panthersButton && compChoice == 1) //player: Paper, comp: Rock
{
gamesWon = gamesWon + 1;
playerScore.setText(""+gamesWon);
gamesPlayed++;
}
else if(e.getSource() == spartansButton && compChoice == 3) //player: Scissors, comp: Scissors
{
gamesTied = gamesTied + 1;
tieScore.setText(""+gamesTied);
gamesPlayed++;
}
else if(e.getSource() == spartansButton && compChoice == 2) //player: Scissors, comp: Paper
{
gamesWon = gamesWon + 1;
playerScore.setText(""+gamesWon);
gamesPlayed++;
}
else if(e.getSource() == spartansButton && compChoice == 1) //player: Scissors, comp: Rock
{
gamesLost = gamesLost + 1;
compScore.setText(""+gamesLost);
gamesPlayed++;
}
}
//else if(e.getSource() == resetButton)
//{
//playerScore = 0;
//compScore = 0;
//tieScore = 0;
//gamesWon.setText(""+playerScore);
//gamesLost.setText(""+compScore);
//gamesTied.setText(""+tieScore);
//}
}
private static void createAndShowGUI()
{
JFrame.setDefaultLookAndFeelDecorated(true);
JFrame frame = new JFrame("[=] JButton Scores! [=]");
RPSGraphics demo = new RPSGraphics();
frame.setContentPane(demo.createContentPane());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(280, 190);
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
错误：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.awt.Container.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at RPSGraphics.createContentPane(RPSGraphics.java:70)
at RPSGraphics.createAndShowGUI(RPSGraphics.java:202)
at RPSGraphics.access$0(RPSGraphics.java:194)
at RPSGraphics$1.run(RPSGraphics.java:213)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
答案 0 :(得分：0)
NPE指向这一行（70）：
scorePanel.add(tieScore);
显然，您尚未初始化tieScore