Adding a JPanel to a JCheckBox (that's not a typo)

Question

Happy Friday everyone! Time for another slightly ridiculous question from yours truly.
Long story short, I'm trying to create a JCheckBox with three potential states instead of two: checked, unchecked, and undetermined. My eventual goal is to use this as a renderer in a JTree of options with sub-options, etc.
Don't read this paragraph if you don't care about my ultimate goal and want to get onto the SSCCE: For example, the JTree might contain a node that represents "all animals" and then underneath it is a list of animals. The user would be able to select the "all animals" JCheckBox, which would then select all of the animal JCheckBoxes underneath it (I already have this part working perfectly). However, what should happen when the user goes into the structure and deselects "ducks" from the animal tree? Currently the "all animals" JCheckBox becomes deselected, but this doesn't seem very intuitive to me. So I'd like a third option that basically means "some of my children are selected, some are deselected". (My actual program has nothing to do with animals, but it's a fun example)
The meat and potatoes of the problem: In order to simulate the third state of the JCheckBox, I thought I'd add to it a JPanel that painted an X (or a slash, or whatever means "indeterminate") on itself. The problem is, all sorts of interesting things start happening when I do this. The JPanel is quite large before any repainting goes on. After the first call to repaint (I simulate this by resizing the JFrame a tiny tiny tiny bit), the JPanel isn't visible at all. And after that, only the JPanel is visible.
Am I missing something? Is there a better way to do what I'm trying to do?
The SSCCE:
import javax.swing.JFrame;
import java.awt.Dimension;
import javax.swing.JCheckBox;
import javax.swing.JPanel;
import java.awt.Graphics;
import javax.swing.BoxLayout;
import javax.swing.UIManager;
public class TestCheckBoxPanel{
     public TestCheckBoxPanel(){
          try {
               UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
          catch (Exception e) {
               e.printStackTrace();
          JFrame frame = new JFrame("Testing JCheckBox");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          frame.getContentPane().setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
          JCheckBox regularCheckBox = new JCheckBox("CheckBox", true);
          final JCheckBox panelCheckBox = new JCheckBox("PanelCheckBox", false);
          JPanel panel = new JPanel(){
               public void paintComponent(Graphics g){
                    super.paintComponent(g);
                    //this almost works, but what happens if the JCheckBox
                    //is a different size on a different computer?
                    //is that even possible?
                    setMinimumSize(new Dimension(10, 10));
                    setMaximumSize(new Dimension(10, 10));
                    setPreferredSize(new Dimension(10, 10));
                    //this makes the JPanel huge, and makes me cry
                    setMinimumSize(new Dimension(panelCheckBox.getWidth(), panelCheckBox.getHeight()));
                    setMaximumSize(new Dimension(panelCheckBox.getWidth(), panelCheckBox.getHeight()));
                    setPreferredSize(new Dimension(panelCheckBox.getWidth(), panelCheckBox.getHeight()));
                    g.drawLine(0, 0, getWidth(), getHeight());
                    g.drawLine(getWidth(), 0, 0, getHeight());
               } //end paintComponent
          }; //end new JPanel
          panelCheckBox.add(panel);
          frame.add(regularCheckBox);
          frame.add(panelCheckBox);
          frame.pack();
          frame.setVisible(true);     
     public static void main(String [] args){
          new TestCheckBoxPanel();
}

Answer 1

jduprez wrote:
Hello,
First thank you for the humourous wording.Haha, I figure if I'm going to ask ridiculous questions, the least I can do is ask them in an entertaining way!
Admittedly though, your problem is more complex than it seem.That's what I was afraid of :(
I don't see you setting the layout of the JCheckbox (viewed as a Container of the JPanel). I tried experimenting with setting the JCheckBox's layout. Using a null layout and absolute positioning actually ends up with a monstrous looking cut-in-half JCheckBox with no text.
Arguably, you know that the bounds are initially (0,0,0,0), but relying on the 0,0 origin assumes the box is always on the left side (which is not true as a JCheckbox can have a different alignment/orientation/don't remember the term.That should actually be okay, I can assume that the box will be on the left side for these purposes.
Moreover, setting the size with a fixed value does not account for what may happen to the checkbox if you stretch it, change the font, change the spacing,...Exactly. That's why I wanted to use the JCheckBox's width and height, which ends up making the JPanel quite large instead of just the size of the box. I'd much rather prefer using a width and height that would change with the JCheckBox's size.
When you say you have already dealt with the 3-state problem, you mean you have designed a custom model? Sort of. I wrote a custom renderer and nodes for my JTree. Each node contains its state (selected, deselected, and undetermined) which changes when the user selects a node in the JTree, and the renderer is to return a Component based on that status. The setting of the state works fine, it's just figuring out what the renderer should return.
Then your component is no more a JCheckbox. I mean, do you still need that it extends JCheckbox?That's a good point. I was using a JCheckBox just because it seemed like the most logical/intuitive component, but I could use anything. The node's selected status is independent of the JCheckBox's selected status (I set the JCheckBox based off the node's state).
If not, one thing you could try is to implement a 3StateCheckBox as a JPanel, which contains...I think what I might try to do is simply use a JLabel with an icon, and then have three separate icons for the three states (I might even use images of JCheckBoxes, haha).