Need some info on menus

I am interested in learning how to do drop down menus in my Java GUI's. I just need some information before i get started

What classes are needing for drop down menus? How does Java respond to a menu selection? Does it use a ListSelectionListener or an ActionEventListener?

Can I see a very simple example of a drop down menu.

If you use Swing, which is what I would recommend, use JComboBox:

Code:

---

JComboBox jcb = new JComboBox();
jcb.addActionListener(this);


then to add stuff to it:

jcb.addItem("One");
jcb.addItem("Two");


in the actionPeformed method:
I would do this:

        String strWhich = (String)jcb.getSelectedItem();

if (strWhich  == "One")
{
  //do something
}

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I do have an example from a while back that converts currency, let me know if your interested in seeing it.

Do you mean a combo box or a menu? Here is an example if a menu is what you want :

Code:

---

import java.awt.*;
import java.awt.event.*;

public class TestMenu extends Frame {//implements ActionListener{

        public static void main(String args[]) {
                TestMenu T=new TestMenu("Window title");
                T.pack();
                T.show();
        }

        public TestMenu(String title) {
                super(title);

                setLayout(new BorderLayout());

                Button bAdd=new Button("Button");
                add(bAdd);

                FileMenu fileMenu = new FileMenu(this);

                MenuBar mb = new MenuBar();
                mb.add(fileMenu);
                setMenuBar(mb);

                addWindowListener(new WindowAdapter(){
                        public void windowClosing(WindowEvent e) {
                                System.exit(0);
                        }
                });
        }

    public void exit() {
                setVisible(false);
                dispose();
                System.exit(0);
        }

}

class FileMenu extends Menu implements ActionListener {
  TestMenu TM;  // who owns us?
  public FileMenu(TestMenu tm) {
    super("File");
    TM = tm;
    MenuItem mi;
    add(mi = new MenuItem("Exit"));
    mi.addActionListener(this);
  }

  public void actionPerformed(ActionEvent e) {
    String item = e.getActionCommand();
    if (item.equals("Exit")) {
                TM.exit();
    } else {
      System.out.println("Selected FileMenu " + item);
        }
  }
}

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Maybe that's what he meant!

Just for addition to Phillip's post. You can do it like this on swing

VB Code:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class test extends JFrame{
    JMenuBar mbar=new JMenuBar();
    JMenu mnufile=new JMenu("File");
    JMenuItem mnuexit=new JMenuItem("Exit");
    public test(){
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(300,300);
 
        setJMenuBar(mbar);
        mbar.add(mnufile);
        mnufile.add(mnuexit);
 
        mnuexit.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e){
                mnuexit_actionPerformed(e);
            }
        });
    }
    void mnuexit_actionPerformed(ActionEvent e){
        System.exit(0);
    }
 
    public static void main(String[] args){
        new test().setVisible(true);
    }
}

Btw, show is deprecated, so refrain from using it. Also I created the mnuexit_actionPerformed on the class' scope. This is just for some use. You can access it from within the class.

I wanted a menu, not a combo box. Kinda like the menu that we all have in our internet browsers. you know, FILE, EDIT, VIEW, etc.

Ok, i was tinkering around with this and I wanted to just make an ActionPerformed method, not an abstract method. The problem comes up when i try to add the actionlistener to my exit JMenuItem.

mnuexit.addActionListener(this);

I get this error

Quote:

---

addActionListener(java.awt.event.ActionListener) in javax.swing.AbstractButton cannot be applied to (TestMenu2)

---

Code:

---

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class TestMenu2 extends JFrame{
        JMenuBar mbar=new JMenuBar();//creates the menu bar
       
        JMenu mnufile=new JMenu("File");//creates the file selection of the menu bar
        JMenuItem mnuexit=new JMenuItem("Exit");//creates the options for the file menu

        JMenu mnuEdit = new JMenu("Edit");//create the edit selection of the menu bar
        JMenuItem mnuCopy=new JMenuItem("Copy");//creates the options for the file menu

       
        public TestMenu2(){
                setDefaultCloseOperation(EXIT_ON_CLOSE);
                setSize(300,300);

                setJMenuBar(mbar);
                mbar.add(mnufile);//adds "File"
                mnufile.add(mnuexit);//adds "Exit" option for the file selection
               
                mbar.add(mnuEdit);//adds "Edit"
                mnuEdit.add(mnuCopy);//adds copy to Edit

                mnuexit.addActionListener(this);
        }
       
        public void actionPerformed(ActionEvent e){
                if(e.getSource()=="Exit"){
                        System.exit(0);               
                }
        }

        public static void main(String[] args){
                new TestMenu2().setVisible(true);
        }
}

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you didn't implement the actionListener?