How to set image as background of JTree component

[sasi kala]

Hi Friends,

i was involved in developing a swing project. In that a need to set background of JTree with a custom image. i had done some coding for that, but this code draws image onto the tree not as background to tree.

  class MyTree extends JTree
  {
   public void paint(java.awt.Graphics g)
   {
       super.paint(g);
 
        Image img;
        img = new ImageIcon(getClass().getResource("/background.jpg")).getImage();                
 
        g.drawImage(img,10,10,100,100,null);
    }
  }
  

My Question is how to set image as background of JTree.
Please help me

sasikala

[Gregg Bolinger]

The way I would do it is put the image on the container (JPanel) that the JTree is a child of. Then set the opageness of the JTree to false ( tree.setOpaque(false) ). This will give you the desired affect.

Another option *might* be to sublcass JTree and override it's paintComponent method and draw the image there instead of on the container. However, drawing it on the container is better, IMO.

[Craig Wood]

This line

img = new ImageIcon(getClass().getResource("/background.jpg")).getImage();

will load the image again each time the paint code executes. To see how often this can happen add a marker, like System.out.println("yo");, in the paint method and hide/show, minimize/restore or partially cover and uncover the top–level container. We only need to load it once. I would move the line to a class constructor.

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.tree.*;
 
public class TreeBackground
{
    public TreeBackground()
    {
        JTree tree = new JTree(getTreeModel())
        {
            BufferedImage image = loadImage();
 
            protected void paintComponent(Graphics g)
            {
                int w = getWidth();
                int h = getHeight();
                int imageWidth = image.getWidth();
                int imageHeight = image.getHeight();
                int x = (w - imageWidth)/2;      // to center image
                int y = (h - imageHeight)/2;     //   in background
                g.drawImage(image, x, y, this);  // render image
                super.paintComponent(g);         // render the tree
            }
        };
        tree.setOpaque(false);
        Color bgColor = UIManager.getColor("Panel.background");
        DefaultTreeCellRenderer renderer = 
                (DefaultTreeCellRenderer)tree.getCellRenderer();
        renderer.setBackgroundNonSelectionColor(bgColor);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(tree);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    private DefaultTreeModel getTreeModel()
    {
        String[] birds = {
            // branches |<-- child leaf nodes -->|
            "hawks", "gray", "red-tailed", "rough-legged",
            "falcons", "harrier", "kestrel", "kite", 
            "owls", "barred", "saw-whet", "snowy"
        };
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("birds");
        DefaultMutableTreeNode[] nodes = new DefaultMutableTreeNode[birds.length];
        for(int j = 0; j < nodes.length; j++)
            nodes[j] = new DefaultMutableTreeNode(birds[j]);
        for(int j = 0; j < 9; j += 4)
        {
            root.insert(nodes[j], j % 3);
            for(int k = j + 1; k < j + 4; k++)
                nodes[j].insert(nodes[k], k - j - 1);
        }
        return new DefaultTreeModel(root);
    }
 
    private BufferedImage loadImage()
    {
        String fileName = "images/cougar.jpg";
        BufferedImage image = null;
        try
        {
            URL url = getClass().getResource(fileName);
            image = ImageIO.read(url);
        }
        catch(MalformedURLException mue)
        {
            System.err.println("url: " + mue.getMessage());
        }
        catch(IOException ioe)
        {
            System.err.println("read: " + ioe.getMessage());
        }
        return image;
    }
 
    public static void main(String[] args)
    {
        new TreeBackground();
    }
}

[Gregg Bolinger]

That's a good solution Craig. In my suggested solution, I didn't take into account putting the JTree on a JScrollPane which would make my solution more difficult.

[sasi kala]

hi Craig Wood & Gregg Bolinger,

Thank you very much. it is working, i couldn't believe this after seeing the result also. setting multi color and image both are working.

once again thank you very much.

Sasikala.