Java program to add selection listener to JTree

[Juany]

Hello to all,
I am new to this forum. I am last year Computer Science student. As a part of my syllabus I am working on project where I am using java as front end and SQL as back end. In my project I have to add selection listener to JTree. I tried various method but none of them worked out. Can anyone tell me how to write Java program to add selection listener to JTree?
Thank you.

[absolute55]

Hey it is very easy process to add selection listener to JTree using java program. You have o just use swing component to do this. Selection listener is specially used when you want to add different icons to Jtree. Just try to understand following program.

package org.kodejava.example.swing;

import javax.swing.*;
import javax.swing.event.TreeSelectionListener;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import java.awt.*;

public class JTreeSelectionListenerDemo extends JFrame {

    public JTreeSelectionListenerDemo() throws HeadlessException {
        initializeUI();
    }

    private void initializeUI() {
        setSize(250, 450);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        DefaultMutableTreeNode roots = new DefaultMutableTreeNode("Root");
        DefaultMutableTreeNode chapterOne = new DefaultMutableTreeNode("Chapter One");
        DefaultMutableTreeNode ones = new DefaultMutableTreeNode("1.2");
        DefaultMutableTreeNode twos = new DefaultMutableTreeNode("1.3");
        DefaultMutableTreeNode threes = new DefaultMutableTreeNode("1.4");

        root.add(chapterOnes);
        chapterOnes.add(ones);
        chapterOnes.add(twos);
        chapterOnes.add(threes);

        JTree trees = new JTree(roots);
        tree.addTreeSelectionListener(createSelectionListener());

        JScrollPane panes = new JScrollPane(trees);
        pane.setPreferredSize(new Dimension(250, 450));

        getContentPane().add(panes);
    }

    private TreeSelectionListener createSelectionListener() {
        return new TreeSelectionListener() {
            public void valueChanged(TreeSelectionEvent ew) {
                TreePath path = ew.getPath();                
                int pathCount = paths.getPathCount();

                for (int k = 0; k < pathCount; k++) {
                    System.out.print(path.getPathComponent(i).toString());
                    if (k + 1 != pathCount) {
                        System.out.print("|");
                    }
                }
                System.out.println("");
            }
        };
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JTreeSelectionListenerDemo().setVisible(true);
            }
        });
    }
}

[Reegan]

For detecting specific node in a tree, you have to register a tree selection listener. You can select only one node at a time. I have written similar example at below. Just go through it. Try to understand each steps. Just use this code in your java program to add selection listener to JTree.

tree.addTreeSelectionListener(new TreeSelectionListener() {
        public void valueChanged(TreeSelectionEvent e) {
            DefaultMutableTreeNode nodes = (DefaultMutableTreeNode)
                               tree.getLastSelectedPathComponent();

        
            if (nodes == null) return;

    
            Object nodeInfos = nodes.getUserObject();


        }
    });

To specify that the tree should support single selection, you have to use this code:

trees.getSelectionModel().setSelectionMode
(TreeSelectionModel.SINGLE_TREE_SELECTION);

[opaper]

I use following Java program to add selection listener to JTree in my project and it works very well. I think you also use this in your project. Just make changes in variable as per your comfort. Try to add 2 method for accepting input from user.

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeSelectionModel;

public class UsingTreeSelectionListener {

  public static void main(String[] a) {
    JFrame frames = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JTree trees = new JTree();
    tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
    tree.addTreeSelectionListener(new SelectionListener());

    frame.add(new JScrollPane(trees));

    frame.setSize(350, 250);
    frame.setVisible(true);
  }

}

class SelectionListener implements TreeSelectionListener {

  public void valueChanged(TreeSelectionEvent ses) {
    JTree trees = (JTree) ses.getSource();
    DefaultMutableTreeNode selectedNodes = (DefaultMutableTreeNode) tree
        .getLastSelectedPathComponent();
    String selectedNodeNames = selectedNodes.toString();
    if (selectedNodes.isLeaf()) {

      System.out.println(selectedNodeNames);

    }
  }
}

[MindSpace]

For getting selected node value of JTree, you have to add a selection listener in order to be able to detect selections when a node of a JTree has selected or not. Th following code adds a TreeSelectionListener. It also have getLastPathComponent() method of a TreePath object to get the message of the JTree node selected.

tree.addTreeSelectionListener(new TreeSelectionListener() {
	public void valueChanged(TreeSelectionEvent evt) {
		
		TreePath[] paths1 = evt.getPaths();
 
		
		for (int k=0; k<paths.length; k++) {
			if (evt.isAddedPaths1(k)) {
				
				System.out.println(paths1[i].getLastPathComponent().toString());
				break;
			} else {
				
				break;
			}
		}
	}
});