JAVA JMENU INTRODUCTION
Java Swing Tutorial Explaining the JMenuBar Component. Swing provides support for pull-down and popup menus. A JMenubar can contain several JMenu ‘s. Each of the JMenu ‘s can contain a series of JMenuItem ‘s that you can select.
How Menu’s Are Created?
1. First, A JMenubar is created
2. Then, we attach all of the menus to this JMenubar.
3. Then we add JMenuItem ‘s to the JMenu ‘s.
4. The JMenubar is then added to the frame. By default, each JMenuItem added to a JMenu is enabled—that is, it can be
selected. In certain situations, we may need to disable a JMenuItem. This is done by calling setEnabled(). The setEnabled()
method also allows components to be enabled.
2. Then, we attach all of the menus to this JMenubar.
3. Then we add JMenuItem ‘s to the JMenu ‘s.
4. The JMenubar is then added to the frame. By default, each JMenuItem added to a JMenu is enabled—that is, it can be
selected. In certain situations, we may need to disable a JMenuItem. This is done by calling setEnabled(). The setEnabled()
method also allows components to be enabled.
JMENU SOURCE CODE
import java.awt.*;
import java.awt.event.*;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.ButtonGroup;
import javax.swing.JMenuBar;
import javax.swing.KeyStroke;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JScrollPane;
import javax.swing.JFrame;
//Used Action Listner for JMenuItem & JRadioButtonMenuItem
//Used Item Listner for JCheckBoxMenuItem
public class JMenuDemo implements ActionListener, ItemListener {
JTextArea jtAreaOutput;
JScrollPane jspPane;
public JMenuBar createJMenuBar() {
JMenuBar mainMenuBar;
JMenu menu1, menu2, submenu;
JMenuItem plainTextMenuItem, textIconMenuItem, iconMenuItem,
subMenuItem;
JRadioButtonMenuItem rbMenuItem;
JCheckBoxMenuItem cbMenuItem;
ImageIcon icon = createImageIcon("jmenu.jpg");
mainMenuBar = new JMenuBar();
menu1 = new JMenu("Menu 1");
menu1.setMnemonic(KeyEvent.VK_M);
mainMenuBar.add(menu1);
// Creating the MenuItems
plainTextMenuItem = new JMenuItem("Menu item with Plain Text",
KeyEvent.VK_T);
// can be done either way for assigning shortcuts
// menuItem.setMnemonic(KeyEvent.VK_T);
// Accelerators, offer keyboard shortcuts to bypass navigating
// the menu hierarchy.
plainTextMenuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_1, ActionEvent.ALT_MASK));
plainTextMenuItem.addActionListener(this);
menu1.add(plainTextMenuItem);
textIconMenuItem = new JMenuItem("Menu Item with Text & Image",
icon);
textIconMenuItem.setMnemonic(KeyEvent.VK_B);
textIconMenuItem.addActionListener(this);
menu1.add(textIconMenuItem);
// Menu Item with just an Image
iconMenuItem = new JMenuItem(icon);
iconMenuItem.setMnemonic(KeyEvent.VK_D);
iconMenuItem.addActionListener(this);
menu1.add(iconMenuItem);
menu1.addSeparator();
// Radio Button Menu items follow a seperator
ButtonGroup itemGroup = new ButtonGroup();
rbMenuItem = new JRadioButtonMenuItem(
"Menu Item with Radio Button");
rbMenuItem.setSelected(true);
rbMenuItem.setMnemonic(KeyEvent.VK_R);
itemGroup.add(rbMenuItem);
rbMenuItem.addActionListener(this);
menu1.add(rbMenuItem);
rbMenuItem = new JRadioButtonMenuItem(
"Menu Item 2 with Radio Button");
itemGroup.add(rbMenuItem);
rbMenuItem.addActionListener(this);
menu1.add(rbMenuItem);
menu1.addSeparator();
// Radio Button Menu items follow a seperator
cbMenuItem = new JCheckBoxMenuItem("Menu Item with check box");
cbMenuItem.setMnemonic(KeyEvent.VK_C);
cbMenuItem.addItemListener(this);
menu1.add(cbMenuItem);
cbMenuItem = new JCheckBoxMenuItem("Menu Item 2 with check box");
cbMenuItem.addItemListener(this);
menu1.add(cbMenuItem);
menu1.addSeparator();
// Sub Menu follows a seperator
submenu = new JMenu("Sub Menu");
submenu.setMnemonic(KeyEvent.VK_S);
subMenuItem = new JMenuItem("Sub MenuItem 1");
subMenuItem.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_2,
ActionEvent.CTRL_MASK));
subMenuItem.addActionListener(this);
submenu.add(subMenuItem);
subMenuItem = new JMenuItem("Sub MenuItem 2");
submenu.add(subMenuItem);
subMenuItem.addActionListener(this);
menu1.add(submenu);
// Build second menu in the menu bar.
menu2 = new JMenu("Menu 2");
menu2.setMnemonic(KeyEvent.VK_N);
mainMenuBar.add(menu2);
return mainMenuBar;
}
public Container createContentPane() {
// Create the content-pane-to-be.
JPanel jplContentPane = new JPanel(new BorderLayout());
jplContentPane.setLayout(new BorderLayout());// Can do it either way
// to set layout
jplContentPane.setOpaque(true);
// Create a scrolled text area.
jtAreaOutput = new JTextArea(5, 30);
jtAreaOutput.setEditable(false);
jspPane = new JScrollPane(jtAreaOutput);
// Add the text area to the content pane.
jplContentPane.add(jspPane, BorderLayout.CENTER);
return jplContentPane;
}
/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = JMenuDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL);
} else {
System.err.println("Couldn't find image file: " + path);
return null;
}
}
private static void createGUI() {
JFrame.setDefaultLookAndFeelDecorated(true);
// Create and set up the window.
JFrame frame = new JFrame("JMenu Usage Demo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JMenuDemo app = new JMenuDemo();
frame.setJMenuBar(app.createJMenuBar());
frame.setContentPane(app.createContentPane());
frame.setSize(500, 300);
frame.setVisible(true);
}
public void actionPerformed(ActionEvent e) {
JMenuItem source = (JMenuItem) (e.getSource());
String s = "Menu Item source: " + source.getText()
+ " (an instance of " + getClassName(source) + ")";
jtAreaOutput.append(s + "\n");
jtAreaOutput.setCaretPosition(jtAreaOutput.getDocument()
.getLength());
}
public void itemStateChanged(ItemEvent e) {
JMenuItem source = (JMenuItem) (e.getSource());
String s = "Menu Item source: "
+ source.getText()
+ " (an instance of "
+ getClassName(source)
+ ")"
+ "\n"
+ " State of check Box: "
+ ((e.getStateChange() == ItemEvent.SELECTED) ?
"selected" : "unselected");
jtAreaOutput.append(s + "\n");
jtAreaOutput.setCaretPosition(jtAreaOutput.getDocument()
.getLength());
}
// Returns the class name, no package info
protected String getClassName(Object o) {
String classString = o.getClass().getName();
int dotIndex = classString.lastIndexOf(".");
return classString.substring(dotIndex + 1); // Returns only Class name
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createGUI();
}
});
}
}
Output
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