Question

For a school project, I need to make a simple paint application that can draw lines, ovals, and rectangles.

The assignment specifies that I need toolbar buttons and menu items for each type of shape.

I would like to go a little above and beyond, by making the buttons JToggleButtons in the toolbar and the menu items JRadioButtonMenuItems. Furthermore, I want it so that when you select one of the toolbar buttons, it deselects the other ones, selects the appropriate menu item, and deselects the other menu items. Same for selecting one of the menu items.

I know I can group any AbstractButton with a ButtonGroup, but I am not sure if this is the right way to go, because though it handles one “group” of buttons just fine, I am not sure it can handle two parallel groups.

Doing it without ButtonGroup would mean in each of the 6 event listeners I would have to manually deselect the other buttons, and each pair would call the same code to set the shape type.

I could also make two ButtonGroups, one for the menu, one for the toolbar, but then I also have to duplicate shape type setting code.

In either situation, I also run the risk of the menu setting a button which sets a menu item which sets a button, ad infintum.

What is the best way to tackle this problem?

(Bonus points for being able to solve the problem with the Netbeans GUI designer; It’s just easier)

Answer 1

The Action interface is an effective approach “if you have two or more components that perform the same function,” as discussed in How to Use Actions. In particular, an Action would allow your buttons and menu items to use the same code.

Addendum: The example below shows how a JMenu and a JToolBar can share the same Action for each of several files.

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.io.File;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JToolBar;

/** @see http://stackoverflow.com/questions/4038605 */
public class FileMenu {

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {

            public void run() {
                new FileMenu().create();
            }
        });
    }

    void create() {
        File userDir = new File(System.getProperty("user.dir"));
        File[] files = userDir.listFiles();

        JMenu menu = new JMenu("Recent Files");
        JToolBar toolBar = new JToolBar(JToolBar.VERTICAL);
        JLabel label = new JLabel(" ", JLabel.CENTER);
        for (File f : files) {
            if (f.isFile() && !f.isHidden()) {
                RecentFile rf = new RecentFile(f, label);
                menu.add(new JMenuItem(rf.getAction()));
                toolBar.add(rf.getAction());
            }
        }
        JMenuBar menuBar = new JMenuBar();
        menuBar.add(menu);

        JFrame f = new JFrame("FileMenu");
        f.setJMenuBar(menuBar);
        f.add(toolBar, BorderLayout.CENTER);
        f.add(label, BorderLayout.SOUTH);
        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }
}

class RecentFile extends AbstractAction {

    private final File file;
    private final JLabel label;

    public RecentFile(final File file, final JLabel label) {
        this.file = file;
        this.label = label;
        this.putValue(Action.NAME, file.getName());
        this.putValue(Action.SHORT_DESCRIPTION, file.getAbsolutePath());
    }

    public void actionPerformed(ActionEvent e) {
        label.setText(file.getName());

    }

    public Action getAction() {
        return this;
    }
}