Tristate Checkboxes in Java

Question

I could really use a tri-stated checkbox in Java. It sounds like a simple thing, but I've only seen really ugly implementations [note: link now broken].

Three radio buttons just take up too much real estate and will probably be confusing for the users in my case. It's basically for a search dialog. I need true, false or "don't care" options. Is there a different technique that people use?

Answer 1

I found a way to make a tri-state checkbox by simply adding a listener:

public class TriStateActionListener implements ActionListener{
    final protected Icon icon;

    public TriStateActionListener(Icon icon){
        this.icon=icon;
    }

    public static Boolean getState(javax.swing.JCheckBox cb){
        if (cb.getIcon()==null) return null;
        if (cb.isSelected()) return true;
        else return false;
    }

    public void actionPerformed(ActionEvent e) {
        javax.swing.JCheckBox cb=(javax.swing.JCheckBox)e.getSource();
        if (!cb.isSelected()){
            cb.setIcon(icon);
        }
        else if (cb.getIcon()!=null){
            cb.setIcon(null);
            cb.setSelected(false);
        }
    }
}

Then in the application code, it's just a single line:

jCheckBox1.addActionListener(new TriStateActionListener(getResourceMap().getIcon("TriStateIcon")));

After all the feedback, I'm thinking a drop-down may be a better choice. But, I wanted to share my code here for everyone else.

Answer 2

Change the UI. Tristate check-box is unusual and can really confuse users. The drop down is good option but for more then one occurrence within dialog it will also bring a lot of confusion to user.

Answer 3

Tristate check-boxes are standard UI idiom for Treeviews with partially checked children nodes. They are widely used in layer management in complex hierarchial views such as Google Earth.

Answer 4

In this implementation the three state can be only set via programmatically. To be Look and Feel portable it use images, that must be placed inside the the same java package.

public class TristateCheckBox extends JCheckBox {

    private static final long serialVersionUID = 1L;
    private boolean halfState;
    private static Icon selected = new javax.swing.ImageIcon(TristateCheckBox.class.getResource("selected.png"));
    private static Icon unselected = new javax.swing.ImageIcon(TristateCheckBox.class.getResource("unselected.png"));
    private static Icon halfselected = new javax.swing.ImageIcon(TristateCheckBox.class.getResource("halfselected.png"));

    @Override
    public void paint(Graphics g) {
        if (isSelected()) {
            halfState = false;
        }
        setIcon(halfState ? halfselected : isSelected() ? selected : unselected);
        super.paint(g);
    }

    public boolean isHalfSelected() {
        return halfState;
    }

    public void setHalfSelected(boolean halfState) {
        this.halfState = halfState;
        if (halfState) {
            setSelected(false);
            repaint();
        }
    }
}

Sample frame:

public class NewJFrame19 extends javax.swing.JFrame {

    private final TristateCheckBox myCheckBox;

    public NewJFrame19() {
        myCheckBox = new TristateCheckBox();
        myCheckBox.setText("123123");
        add(myCheckBox);

        jButton1 = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(new java.awt.FlowLayout());

        jButton1.setText("jButton1");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
        getContentPane().add(jButton1);

        pack();
    }

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        myCheckBox.setHalfSelected(true);
    }                                        

    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Windows".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame19.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame19.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame19.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame19.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame19().setVisible(true);
            }
        });
    }
    private javax.swing.JButton jButton1;
}

Answer 5

That "ugly implementations" is an old link. One of the suggestions on that page was updated a couple of years ago. I haven't tested the old implementation, so I don't know if the new one is any better or worse.

TristateCheckBox Revisited

Answer 6

I dont know why anyone would give the solutions with additional icon png files while java api gives great funcionality for overriding paintIcon(..) method.

The best lightweight solution to remember CheckBox state is IMO ClientProperty attribute.

/*
 * Tri-state checkbox example
 * @s1w_
*/
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;


class TCheckBox extends JCheckBox implements Icon, ActionListener {

    final static boolean MIDasSELECTED = true;  //consider mid-state as selected ?


    public TCheckBox() { this(""); }

    public TCheckBox(String text) {
        super(text);
        putClientProperty("SelectionState", 0);
        setIcon(this);
        addActionListener(this);
    }

    public TCheckBox(String text, int sel) {
        /* tri-state checkbox has 3 selection states:
         * 0 unselected
         * 1 mid-state selection
         * 2 fully selected
        */
        super(text, sel > 1 ? true : false);

        switch (sel) {
            case 2: setSelected(true);
            case 1:
            case 0:
                putClientProperty("SelectionState", sel);
                break;
           default:
                throw new IllegalArgumentException();
        }
        addActionListener(this);
        setIcon(this);
    }

    @Override
    public boolean isSelected() {
        if (MIDasSELECTED && (getSelectionState() > 0)) return true;
        else return super.isSelected();
    }

    public int getSelectionState() {
        return (getClientProperty("SelectionState") != null ? (int)getClientProperty("SelectionState") :
                                         super.isSelected() ? 2 :
                                         0);
    }

    public void setSelectionState(int sel) {
        switch (sel) {
            case 2: setSelected(true);
                    break;
            case 1: 
            case 0: setSelected(false);
                    break;
           default: throw new IllegalArgumentException();
        }
        putClientProperty("SelectionState", sel);
    }


    final static Icon icon = UIManager.getIcon("CheckBox.icon");

    @Override
    public void paintIcon(Component c, Graphics g, int x, int y) {
        icon.paintIcon(c, g, x, y);
        if (getSelectionState() != 1) return;

        int w = getIconWidth();
        int h = getIconHeight();
        g.setColor(c.isEnabled() ? new Color(51, 51, 51) : new Color(122, 138, 153));
        g.fillRect(x+4, y+4, w-8, h-8);

        if (!c.isEnabled()) return;
        g.setColor(new Color(81, 81, 81));
        g.drawRect(x+4, y+4, w-9, h-9);
    }

    @Override
    public int getIconWidth() {
        return icon.getIconWidth();
    }

    @Override
    public int getIconHeight() {
        return icon.getIconHeight();
    }

    public void actionPerformed(ActionEvent e) {
        TCheckBox tcb = (TCheckBox)e.getSource();
        if (tcb.getSelectionState() == 0)
            tcb.setSelected(false);

        tcb.putClientProperty("SelectionState", tcb.getSelectionState() == 2 ? 0 :
                                                     tcb.getSelectionState() + 1);

        // test
        System.out.println(">>>>IS SELECTED: "+tcb.isSelected());
        System.out.println(">>>>IN MID STATE: "+(tcb.getSelectionState()==1));
    }
}

usage: TCheckBox tcb = new TCheckBox("My CheckBox");