PulsePanda PulsePanda - 6 months ago 18
Java Question

How to make a JMenu item do something when it's clicked

I'm making a GUI that has a Jmenu; it has the jmenu items that will be doing things when clicked. That is the problem. I've looked and looked, but I can't find out how to make it do something when clicked. Also, I am kind of a noob, so if you could make it do it in a pretty simple way, that would be great!

Here's the code:

import java.awt.Color;
import java.awt.Component;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.*;

public abstract class windowMaker extends JFrame implements ActionListener {
private JMenu menuFile;

public static void main(String[] args) {
createWindow();

}

public static void createWindow() {
JFrame frame = new JFrame();
frame.setTitle("*Game Title* Beta 0.0.1");
frame.setSize(600, 400);
frame.setLocation(100, 100);
frame.setVisible(true);
frame.setResizable(false);
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.setJMenuBar(windowMaker.menuBarCreator());
frame.add(windowMaker.setTitle());
}

public static void launchURL(String s) {
String s1 = System.getProperty("os.name");
try {

if (s1.startsWith("Windows")) {
Runtime.getRuntime()
.exec((new StringBuilder())
.append("rundll32 url.dll,FileProtocolHandler ")
.append(s).toString());
} else {
String as[] = { "firefox", "opera", "konqueror", "epiphany",
"mozilla", "netscape" };
String s2 = null;
for (int i = 0; i < as.length && s2 == null; i++)
if (Runtime.getRuntime()
.exec(new String[] { "which", as[i] }).waitFor() == 0)
s2 = as[i];

if (s2 == null)
throw new Exception("Could not find web browser");
Runtime.getRuntime().exec(new String[] { s2, s });
}
} catch (Exception exception) {
System.out
.println("An error occured while trying to open the web browser!\n");
}
}

public static JMenuBar menuBarCreator() {
// create the menu parts
JMenuBar menuBar = new JMenuBar();
JMenu menuFile = new JMenu("File");
JMenu menuHelp = new JMenu("Help");
JMenuItem menuFileWebsite = new JMenuItem("Website");
JMenuItem menuFileExit = new JMenuItem("Exit");
JMenuItem menuHelpRules = new JMenuItem("Rules");
JMenuItem menuHelpAbout = new JMenuItem("About");
JMenuItem menuHelpHow = new JMenuItem("How To Play");

// make the shortcuts for the items
menuFile.setMnemonic(KeyEvent.VK_F);
menuHelp.setMnemonic(KeyEvent.VK_H);

// put the menu parts with eachother
menuBar.add(menuFile);
menuBar.add(menuHelp);
menuFile.add(menuFileWebsite);
menuFile.add(menuFileExit);
menuHelp.add(menuHelpRules);
menuHelp.add(menuHelpAbout);
menuHelp.add(menuHelpHow);


return menuBar;
}

public static Component setTitle() {
JLabel title = new JLabel("Welcome To *the game*");
title.setVerticalAlignment(JLabel.TOP);
title.setHorizontalAlignment(JLabel.CENTER);
return title;
}

}


BTW: I want the website option (let's just work with that for now) to use the launchURL method; I know that one works.

Answer

A JMenuItem is a form of a button (AbstractButton). The normal pattern is to construct your button with an Action (see JMenuItem's constructor). The Action defines the name and action to be performed. Most people extend AbstractAction and implement actionPerformed which is invoked when the button is pressed.

A possible implementation might look like:

JMenuItem menuItem = new JMenuItem(new AbstractAction("My Menu Item") {
    public void actionPerformed(ActionEvent e) {
        // Button pressed logic goes here
    }
});

or:

JMenuItem menuItem = new JMenuItem(new MyAction());
...
public class MyAction extends AbstractAction {
    public MyAction() {
        super("My Menu Item");
    }

    public void actionPerformed(ActionEvent e) {
        // Button pressed logic goes here
    }
}

Note that everything I said above also applies to JButton. Also take a look at Java's very helpful How to Use Actions tutorial.