可能重复：
运行Java程序时出错
我目前正在使用eclipse编写一个java程序。我听说使用netbeans制作java gui更容易，所以我想尝试使用netbeas完成这个java程序。然而，当我使用netbeans打开我的项目并运行它时，它会给我一个错误。我打算使用betbeans运行与eclipse下运行良好的程序相同的程序。
这就是错误：
run:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:181)
at MainForm.addComponentsToPane(MainForm.java:28)
at MainForm.createAndShowGUI(MainForm.java:112)
at MainForm.access$000(MainForm.java:15)
at MainForm$4.run(MainForm.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
at java.awt.EventQueue.access$000(EventQueue.java:84)
at java.awt.EventQueue$1.run(EventQueue.java:602)
at java.awt.EventQueue$1.run(EventQueue.java:600)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
BUILD SUCCESSFUL (total time: 8 seconds)
这是正在运行的代码：
import java.awt.Color;
import java.awt.Container;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class MainForm {
public static void addComponentsToPane(final JFrame frame, Container pane) {
Color colorGreen = new Color(0, 100, 0);
Color colorBrown = new Color(150, 100, 0);
//Color colorBlue = new Color (0, 0, 150);
//Font font = new Font("Verdana", Font.BOLD, 12);
pane.setLayout(null);
pane.setBackground(new Color (255, 255, 170));
//add image and necessary labels on top left corner
//SHA Image and label
ImageIcon image = new ImageIcon(MainForm.class.getResource("SHA_logo.gif"));
JLabel label = new JLabel("Office of Traffic & Safety", image, JLabel.LEFT);
label.setVerticalTextPosition(JLabel.BOTTOM);
label.setHorizontalTextPosition(JLabel.CENTER);
label.setFont(new Font("Times New Roman", Font.PLAIN, 11));
pane.add(label);
label.setBounds(50, 10, 130, 100);
label.setBorder(null);
//university of maryland image and label\
image = new ImageIcon(MainForm.class.getResource("maryland_flag_round.gif"));
label = new JLabel("Univ. of Maryland", image, JLabel.LEFT);
label.setVerticalTextPosition(JLabel.BOTTOM);
label.setHorizontalTextPosition(JLabel.CENTER);
label.setFont(new Font("Times New Roman", Font.PLAIN, 11));
pane.add(label);
label.setBounds(190, 10, 130, 90);
label.setBorder(null);
//critical lane label
label = new JLabel("Critical Lane Volume");
label.setFont(new Font("Arial Narrow", Font.BOLD, 30));
label.setForeground(colorGreen);
pane.add(label);
label.setBounds(50, 90, 250, 50);
label.setBorder(null);
label = new JLabel("<html>Please choose the analysis type:</html>");
label.setFont(new Font("Arial", Font.BOLD, 18));
label.setForeground(colorBrown);
pane.add(label);
label.setBounds(25, 130, 300, 70);
label.setBorder(null);
//back and exit buttons
JButton button1 = new JButton("DIAT");
JButton button2 = new JButton ("Intersection");
JButton button3 = new JButton ("Exit");
pane.add(button1);
pane.add(button2);
pane.add(button3);
button1.setBounds(75, 200, 200, 50);
button2.setBounds(75, 270, 200, 50);
button3.setBounds(75, 340, 200, 50);
//add attap label at bottom left
image = new ImageIcon(MainForm.class.getResource("attap_logo.gif"));
label = new JLabel(image);
pane.add(label);
label.setBounds(30, 380, 270, 90);
label.setBorder(null);
button1.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent arg0) {
frame.setVisible(false);
frame.dispose();
InterchangeLoad.main(null);
}
});
button2.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent arg0) {
frame.setVisible(false);
frame.dispose();
MultipleIntersectionLoad.main(null);
}
});
button3.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent arg0) {
frame.setVisible(false);
frame.dispose();
}
});
}
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("Critical Lane Volume");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Set up the content pane.
addComponentsToPane(frame, frame.getContentPane());
frame.setSize(350, 500);
frame.setResizable(false);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
它找不到您的图像。你确定你的图像处于相同的相对位置吗？它们是否与MainForm.class文件位于同一位置？此外，我对使用NetBeans创建GUI比Eclipse更容易的评论表示异议。我已经使用了这两种软件，发现两者都很好用，但我建议您在熟悉Swing之前不要使用任何代码生成软件。例如，您最好学习如何使用Swing/AWT布局管理器，并避免使用null布局/setBounds。
您的程序找不到文件"SHA_logo.gif"，因此您的new ImageIcon(...)是new ImageIcon(null)，这导致了NullPointerException。