How to create a JButton with a menu?

问题:

I want to create a Toolbar in my application. If you click a button on that toolbar, it will pop up a menu, just like in Eclipse's toolbar. I don't know how to do this in Swing. Can someone help me please? I've tried Google but found nothing.

回答1:

This is way harder in Swing than it needs to be. So instead of pointing you to tutorials I've created a fully working example.

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

public class ToolbarDemo {

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setPreferredSize(new Dimension(600, 400));
        final JToolBar toolBar = new JToolBar();

        //Create the popup menu.
        final JPopupMenu popup = new JPopupMenu();
        popup.add(new JMenuItem(new AbstractAction("Option 1") {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frame, "Option 1 selected");
            }
        }));
        popup.add(new JMenuItem(new AbstractAction("Option 2") {
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frame, "Option 2 selected");
            }
        }));

        final JButton button = new JButton("Options");
        button.addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                popup.show(e.getComponent(), e.getX(), e.getY());
            }
        });
        toolBar.add(button);

        frame.getContentPane().add(toolBar, BorderLayout.NORTH);
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

回答2:

I don't see why this is harder than it needs to be or why you should use a MouseListener. The solution by Steve McLeod works, but where the menu appears depends on where the mouse was clicked. Why not just use an ActionListener as normally used for a JButton. It seems neither harder nor less hard.

final JPopupMenu menu = new JPopupMenu();
menu.add(...whatever...);

final JButton button = new JButton();
button.setText("My Menu");
button.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent ev) {
        menu.show(button, button.getBounds().x, button.getBounds().y
           + button.getBounds().height);
    }
});

This positions the menu about the same as a menu in a JMenuBar for me, and the position is consistent. You could place it differently by modifying the x and y in menu.show().

回答3:

I think it's the same as in AWT.

You should put an ActionCommand on that button and when it's executed show the pop-up menu according to the mouse coordinates.

回答4:

See the section Bringing Up a Popup Menu, in How to Use Menus.

回答5:

I'm not sure I understand you correctly but if you want to know how to make toolbars in Swing check this

Java Tutorials: How to Use Tool Bars and this

Java Tutorials: How to Use Actions

回答6:

Here is a simple and nice class

import javax.swing.JPopupMenu;
import javax.swing.JToggleButton;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class MenuButton extends JToggleButton {

    JPopupMenu popup;

    public MenuButton(String name, JPopupMenu menu) {
        super(name);
        this.popup = menu;
        addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ev) {
                JToggleButton b = MenuButton.this;
                if (b.isSelected()) {
                    popup.show(b, 0, b.getBounds().height);
                } else {
                    popup.setVisible(false);
                }
            }
        });
        popup.addPopupMenuListener(new PopupMenuListener() {
            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {}
            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
                MenuButton.this.setSelected(false);
            }
            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {}
        });
    }
}