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 * and open the template in the editor.
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package org.meteoinfo.ui;

import javax.swing.*;
import javax.swing.event.ChangeListener;
import javax.swing.plaf.ActionMapUIResource;
import java.awt.event.*;

/**
 * Maintenance tip - There were some tricks to getting this code working:
 *
 * 1. You have to overwite addMouseListener() to do nothing 2. You have to add a
 * mouse event on mousePressed by calling super.addMouseListener() 3. You have
 * to replace the UIActionMap for the keyboard event "pressed" with your own
 * one. 4. You have to remove the UIActionMap for the keyboard event "released".
 * 5. You have to grab focus when the next state is entered, otherwise clicking
 * on the component won't get the focus. 6. You have to make a TristateDecorator
 * as a button model that wraps the original button model and does state
 * management.
 */
public class TristateCheckBox extends JCheckBox {

    /**
     * This is a type-safe enumerated type
     */
    public static class State {

        private State() {
        }
    }
    public static final State NOT_SELECTED = new State();
    public static final State SELECTED = new State();
    public static final State DONT_CARE = new State();
    private final TristateDecorator model;

    public TristateCheckBox(String text, Icon icon, State initial) {
        super(text, icon);
        // Add a listener for when the mouse is pressed
        super.addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                grabFocus();
                model.nextState();
            }
        });
        // Reset the keyboard action map
        ActionMap map = new ActionMapUIResource();
        map.put("pressed", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent e) {
                grabFocus();
                model.nextState();
            }
        });
        map.put("released", null);
        SwingUtilities.replaceUIActionMap(this, map);
        // set the model to the adapted model
        model = new TristateDecorator(getModel());
        setModel(model);
        setState(initial);
    }

    public TristateCheckBox(String text, State initial) {
        this(text, null, initial);
    }

    public TristateCheckBox(String text) {
        this(text, DONT_CARE);
    }

    public TristateCheckBox() {
        this(null);
    }

    /**
     * No one may add mouse listeners, not even Swing!
     */
    @Override
    public void addMouseListener(MouseListener l) {
    }

    /**
     * Set the new state to either SELECTED, NOT_SELECTED or DONT_CARE. If state
     * == null, it is treated as DONT_CARE.
     */
    public void setState(State state) {
        model.setState(state);
    }

    /**
     * Return the current state, which is determined by the selection status of
     * the model.
     */
    public State getState() {
        return model.getState();
    }

    public void setSelected(boolean b) {
        if (b) {
            setState(SELECTED);
        } else {
            setState(NOT_SELECTED);
        }
    }

    /**
     * Exactly which Design Pattern is this? Is it an Adapter, a Proxy or a
     * Decorator? In this case, my vote lies with the Decorator, because we are
     * extending functionality and "decorating" the original model with a more
     * powerful model.
     */
    private class TristateDecorator implements ButtonModel {

        private final ButtonModel other;

        private TristateDecorator(ButtonModel other) {
            this.other = other;
        }

        private void setState(State state) {
            if (state == NOT_SELECTED) {
                other.setArmed(false);
                setPressed(false);
                setSelected(false);
            } else if (state == SELECTED) {
                other.setArmed(false);
                setPressed(false);
                setSelected(true);
            } else { // either "null" or DONT_CARE
                other.setArmed(true);
                setPressed(true);
                setSelected(true);
            }
        }

        /**
         * The current state is embedded in the selection / armed state of the
         * model.
         *
         * We return the SELECTED state when the checkbox is selected but not
         * armed, DONT_CARE state when the checkbox is selected and armed (grey)
         * and NOT_SELECTED when the checkbox is deselected.
         */
        private State getState() {
            if (isSelected() && !isArmed()) {
                // normal black tick
                return SELECTED;
            } else if (isSelected() && isArmed()) {
                // don't care grey tick
                return DONT_CARE;
            } else {
                // normal deselected
                return NOT_SELECTED;
            }
        }

        /**
         * We rotate between NOT_SELECTED, SELECTED and DONT_CARE.
         */
        private void nextState() {
            State current = getState();
            if (current == NOT_SELECTED) {
                setState(SELECTED);
            } else if (current == SELECTED) {
                setState(DONT_CARE);
            } else if (current == DONT_CARE) {
                setState(NOT_SELECTED);
            }
        }

        /**
         * Filter: No one may change the armed status except us.
         */
        @Override
        public void setArmed(boolean b) {
        }

        /**
         * We disable focusing on the component when it is not enabled.
         */
        @Override
        public void setEnabled(boolean b) {
            setFocusable(b);
            other.setEnabled(b);
        }

        /**
         * All these methods simply delegate to the "other" model that is being
         * decorated.
         */
        public boolean isArmed() {
            return other.isArmed();
        }

        @Override
        public boolean isSelected() {
            return other.isSelected();
        }

        @Override
        public boolean isEnabled() {
            return other.isEnabled();
        }

        @Override
        public boolean isPressed() {
            return other.isPressed();
        }

        @Override
        public boolean isRollover() {
            return other.isRollover();
        }

        @Override
        public void setSelected(boolean b) {
            other.setSelected(b);
        }

        @Override
        public void setPressed(boolean b) {
            other.setPressed(b);
        }

        @Override
        public void setRollover(boolean b) {
            other.setRollover(b);
        }

        @Override
        public void setMnemonic(int key) {
            other.setMnemonic(key);
        }

        @Override
        public int getMnemonic() {
            return other.getMnemonic();
        }

        @Override
        public void setActionCommand(String s) {
            other.setActionCommand(s);
        }

        @Override
        public String getActionCommand() {
            return other.getActionCommand();
        }

        @Override
        public void setGroup(ButtonGroup group) {
            other.setGroup(group);
        }

        @Override
        public void addActionListener(ActionListener l) {
            other.addActionListener(l);
        }

        @Override
        public void removeActionListener(ActionListener l) {
            other.removeActionListener(l);
        }

        @Override
        public void addItemListener(ItemListener l) {
            other.addItemListener(l);
        }

        @Override
        public void removeItemListener(ItemListener l) {
            other.removeItemListener(l);
        }

        @Override
        public void addChangeListener(ChangeListener l) {
            other.addChangeListener(l);
        }

        @Override
        public void removeChangeListener(ChangeListener l) {
            other.removeChangeListener(l);
        }

        @Override
        public Object[] getSelectedObjects() {
            return other.getSelectedObjects();
        }
    }
}
