Java, JCheckbox - consume / prevent all events, but still enable

Question

I've got an icon, with a checkbox next to it, contained in a panel. The panel has a hover effect, and I want to select the box when the panel is clicked.

I'd like to consume or prevent all events to the checkbox, only selecting it programatically. I'd like the box to appear "enabled" onscreen, while "behind the scenes" it's pretty much non-functional. (Selection would happen from a click in the panel.)

Further, when I mouse enter/exit the checkbox, I'd like nothing to happen. I've got a hover effect on the panel. Right now, I can enter the panel, but then when I enter the box, the panel exits, and looks un-hovered.

So, how can I prevent all mouse-related activities on this checkbox - enter, exit, click, etc. From previous research I recall the buzzwords "consume events", but I can't seem to drum up the appropriate searches to make this happen :)

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EDIT

This panel (purple) has an icon (hamburger) and a checkbox (UI LAF). I want to hover the panel, not lose the hover when I enter the checkbox, and toggle the checkbox when the (parent) panel is clicked.

Answer 1

Override dispatchEvent() in EventQueue and push() a new instance, which then replaces the old. In your new implementation, invoke super.dispatchEvent() for all events except those related to your checkbox. A related example may be found here, and a complete implementation may be found in Disabled Panel.

Alternatively, use Toolkit.getDefaultToolkit().addAWTEventListener(), as shown here, to elide unwanted events.

Addendum: Also consider this more user friendly alternative that leverages the check box's button model:

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

/** @see https://stackoverflow.com/a/10238761/230513 */
public class PanelClick extends JPanel {

    JCheckBox jcb = new JCheckBox("Check");
    private boolean selected = jcb.isSelected();

    public PanelClick() {
        this.setPreferredSize(new Dimension(320, 240)); // room to click
        this.add(jcb);
        this.addMouseListener(new MouseAdapter() {

            @Override
            public void mousePressed(MouseEvent e) {
                selected = !jcb.isSelected();
                jcb.setSelected(selected);
            }
        });
    }

    private void display() {
        JFrame f = new JFrame("PanelClick");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new PanelClick().display();
            }
        });
    }
}

Answer 2

Could this serve as a solution?

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

public class PanelCheckBox {

    private JPanel panel = new JPanel();
    private JCheckBox checkBox = new JCheckBox();
    private JLabel icon = new JLabel(new SquareIcon());

    private void showGui() {
        final JFrame frame = setupGui();

        SwingUtilities.invokeLater(new Runnable() {
            @Override public void run() { 
                frame.setVisible(true);
            }
        });
    }

    private JFrame setupGui() {
        panel.add(icon);
        panel.add(checkBox);
        panel.setOpaque(true);
        JFrame frame = new JFrame("Hello");
        frame.add(panel, BorderLayout.CENTER);

        setupListeners();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);
        return frame;
    }

    private void setupListeners() {
        panel.addMouseListener(new MouseAdapter() {
            Color origColor = null;
            Color hoverColor = new Color(200, 180, 180);

            @Override public void mouseEntered(MouseEvent me) {
                if (origColor == null) {
                    origColor = panel.getBackground();
                }
                panel.setBackground(hoverColor);
            }

            @Override public void mouseExited(MouseEvent me) {
                Point location = me.getPoint();

                if (!panel.contains(location)) {
                    panel.setBackground(origColor);
                }
            }

            @Override public void mouseClicked(MouseEvent me) {
                checkBox.doClick();
            }
        });
    }

    public static void main(String[] args) {
        PanelCheckBox thing = new PanelCheckBox();
        thing.showGui();
    }

    static class SquareIcon implements Icon {

        @Override
        public void paintIcon(Component cmpnt, Graphics grphcs,
                              int i, int i1) {
            Color origColor = grphcs.getColor();
            grphcs.setColor(Color.BLUE);
            grphcs.fillRect(0, 0, 25, 25);
            grphcs.setColor(origColor);
        }

        @Override public int getIconWidth() { return 25; }

        @Override public int getIconHeight() { return 25; }
    }
}

Answer 3

I'd like the box to appear "enabled" onscreen, while "behind the scenes" it's pretty much non-functional.

I would find it pretty frustrating to repeatedly click a supposedly enabled check-box to see it do ..nothing. Perhaps you should pop a:

JOptionPane.showErrorMessage(checkbox, "Click the panel!"); 

Answer 4

You could override the mouselistener for the checkbox to do nothing:

class MyBox extends JCheckBox {

    @Override
    protected void processMouseEvent(MouseEvent e) {
    //this will prevent all mouse actions 
    }
}

Then just use MyBox instead of checkbox?

Answer 5

My final solution for this was to use an EmptyBorder on the left side of the checkbox, and BlackPanda's mouse listener solution:

public class CheckboxPanel extends JPanel {
    private final JCheckBox checkBox = new JCheckBox();
    private final Image img;

    public CheckboxPanel (final Image img0) {
        super();
        this.img = img0;

        // Left padding of 20 allows mouseovers on image that trigger the box.
        checkBox.setBorder(new EmptyBorder(0, 20, 0, 0)); 

        add(checkBox);

        this.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(final MouseEvent me) {
                checkBox.doClick();
            }
        });
    }

    public JCheckBox getCheckBox() {
        return this.checkBox;
    }

    @Override
    protected void paintComponent(final Graphics g) {
        super.paintComponent(g);
        g.drawImage(img, 0, 0, null);
    }
}