java中jar文件中jmenu中的图像

Question

Dear Stackoverflow Developers i have to load image as an icon to jmenu from jar. I am using the following code . It is throwing the null pointer exception but when i am setting the icon with imageicon class in jframe, it is showing the icon in frame

   try
   {

    JMenu menu= new JMenu("");
    Icon im1= new ImageIcon(getClass.getResource("path of the images");

   menu.setIcon(im1);
  }
  catch(Exception ex)
   {

   }

what is the wrong in this code plz help

Answer 1

• common issue is that ImageIcon , Icon doesn't returns any exception, test for Null value

• Icon im1= new ImageIcon why??? , those are different Java Object , have to test if Icon is instanceof ImageIcon

• read turotial about Icon and JMenu / JMenuItem

• for example

code

import java.awt.BorderLayout;
import java.awt.ComponentOrientation;
import java.awt.Dimension;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.Box;
import javax.swing.Icon;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JSeparator;
import javax.swing.JTextField;
import javax.swing.JTextPane;
import javax.swing.UIManager;
import javax.swing.border.BevelBorder;

public class MenuExample extends JPanel {

    private static final long serialVersionUID = 1L;
    private JTextPane pane;
    private JMenuBar menuBar;

    public MenuExample() {
        menuBar = new JMenuBar();
        JMenu formatMenu = new JMenu("Justify");
        formatMenu.setMnemonic('J');
        formatMenu.setIcon(UIManager.getIcon("OptionPane.errorIcon"));
        MenuAction leftJustifyAction = new MenuAction("Left", UIManager.getIcon("OptionPane.errorIcon"));
        MenuAction rightJustifyAction = new MenuAction("Right", UIManager.getIcon("OptionPane.informationIcon"));
        MenuAction centerJustifyAction = new MenuAction("Center", UIManager.getIcon("OptionPane.warningIcon"));
        MenuAction fullJustifyAction = new MenuAction("Full", UIManager.getIcon("OptionPane.questionIcon"));
        JMenuItem item;
        item = formatMenu.add(leftJustifyAction);
        item.setMnemonic('L');
        item = formatMenu.add(rightJustifyAction);
        item.setMnemonic('R');
        item = formatMenu.add(centerJustifyAction);
        item.setMnemonic('C');
        item = formatMenu.add(fullJustifyAction);
        item.setMnemonic('F');
        menuBar.add(formatMenu);
        menuBar.add(createMenu("Menu 1"));
        menuBar.add(createMenu("Menu 2"));
        menuBar.add(createMenu("Menu 3"));
        menuBar.add(Box.createHorizontalGlue());
        menuBar.add(new JSeparator());
        menuBar.add(new JButton("   Seach ....  "));
        menuBar.add(new JLabel());
        menuBar.add(new JTextField("   Seach ....  "));
        menuBar.add(new JComboBox(new Object[]{"height", "length", "volume"}));
        menuBar.add(createMenu("About"));
        menuBar.setBorder(new BevelBorder(BevelBorder.RAISED));

    }

    private JMenu createMenu(String title) {
        JMenu m = new JMenu(title);
        m.add("Menu item #1 in " + title);
        m.add("Menu item #2 in " + title);
        m.add("Menu item #3 in " + title);
        if (title.equals("About")) {
            m.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
        }
        return m;
    }

    class MenuAction extends AbstractAction {

        public MenuAction(String text, Icon icon) {
            super(text, icon);
        }

        public void actionPerformed(ActionEvent e) {
            try {
                pane.getStyledDocument().insertString(0,
                        "Action [" + e.getActionCommand() + "] performed!\n",
                        null);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    }

    public static void main(String s[]) {
        MenuExample example = new MenuExample();
        example.pane = new JTextPane();
        example.pane.setPreferredSize(new Dimension(250, 250));
        example.pane.setBorder(new BevelBorder(BevelBorder.LOWERED));
        JFrame frame = new JFrame("Menu Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setJMenuBar(example.menuBar);
        frame.getContentPane().add(example.pane, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }
}

Answer 2

What is wrong with this code?

1. An empty catch(Exception ex) block: you should always leave a trace of an exception, otherwise it makes it incredibly hard to debug. Use a logger for that purpose or print the stacktrace to the console)
2. It is very likely that the resource is not found if you can't see the icon. In general, I prefer to use absolute path to the resource (otherwise it is relative to the current class package). You need to ensure that the image file is properly embedded (it must be somewhere on your classpath, either in a jar or in a directory)
3. You should use a consistent indentation.