How do I auto-expand a JTree when setting a new TreeModel?

Question

I have a custom JTree and a custom JModel; I would for the JTree to "auto-expand" when I give it a new model. At the moment, it simply collapse all the nodes to the root.

Here is an example:

private class CustomTree extends JTree {

    @Override
    public boolean isExpanded(TreePath path) {
        return ((Person) path.getLastPathComponent).hasChildren();

}

private class CustomTreeModel extends TreeModel {

    // ... omitting various implementation details

    @Override
    public boolean isLeaf(Object object) {
        return !((Person) object).hasChildren();
    }

}

Model model = new Model();
Person bob = new Person();
Person alice = new Person();
bob.addChild(alice);
model.setRoot(bob);
JTree tree = new CustomTree(new CustomTreeModel(model));

At this point, the tree correctly displays:

- BOB
  - ALICE

where Alice is a child of Bob (both in the data and in the visual tree)

However, if I call:

tree.setModel(new CustomTreeModel(model));

everything is collapsed:

+ BOB

Is there a way to "auto-expand" everything in the tree when setting a new model?

Miracle

no ideas from this code and description, all notifiers & listener go away after model is changed, – Hookworm

@Hookworm I believe my answer below solves my problem. – Miracle

:-) ............... do not use index by int, you can lost this index, have to store all accesible about node inc. Object value (my view) – Hookworm

Expand on setting a new model. For better help sooner, post an SSCCE. – Can

@Hookworm I'm sorry I don't quite understand - I can lose the tree.getRowCount() index? How? – Miracle

@AndrewThompson tree.setModel(new CustomTreeModel(model)) – Miracle

models can be different, tree.getRowCount() <> with old model, or <> structure of nodes, or <> value from one, two or all elements, if yes then don't recreate a model use implemented menthods and notifiers, have you issue with nodeChanged, post an SSCCE, where you replace an new model with different structure, then this question make me sence – Hookworm

Answer 1

I had a similar problem.

Your solution (as posted https://mcmap.net/q/523551/-how-do-i-auto-expand-a-jtree-when-setting-a-new-treemodel) seemed to work for me only for the top level tree nodes.

But I needed to expand all the a descendants node. So I solved it with the following recursive method:

private void expandAllNodes(JTree tree, int startingIndex, int rowCount){
    for(int i=startingIndex;i<rowCount;++i){
        tree.expandRow(i);
    }

    if(tree.getRowCount()!=rowCount){
        expandAllNodes(tree, rowCount, tree.getRowCount());
    }
}

which is invoked with

expandAllNodes(tree, 0, tree.getRowCount());

where, tree is a JTree.

Unless someone has a better solution.

Restaurant

see sdasdadas answer below for a 3 line solution without recursion. – Locale

You're saving the rowCount, then expanding that many lines. But by the time you've expanded them, more lines are added. If you change i<rowCount in your for statement to i<tree.getRowCount(), it will keep expanding from the top, and won't end until it has reached all the expanded rows, no need for recursion. – Cadaverine

Answer 2

The following worked for me (called after setting the new model):

for (int i = 0; i < tree.getRowCount(); i++) {
    tree.expandRow(i);
}

Miracle

@all: this solution is sufficient, here's no need for recursion – Ambler

As for "why": it works because expandRow() will show more rows, making getRowCount() increase after each expansion. Trying to be smart by storing n = getRowCount() and for (i=0; i<n; i++) will not work. – Nutritious

Answer 3

There's also this non-recursive version.

private void expandAllNodes(JTree tree) {
    int j = tree.getRowCount();
    int i = 0;
    while(i < j) {
        tree.expandRow(i);
        i += 1;
        j = tree.getRowCount();
    }
}

Zia

Answer 4

this worked for me..

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreePath;
import javax.swing.tree.TreeNode;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Enumeration;

public class JTreeNodeAutoExpandCollapse extends JFrame {
    public JTreeNodeAutoExpandCollapse() throws HeadlessException {
        initializeUI();
    }

    private void initializeUI() {
        setSize(200, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
        DefaultMutableTreeNode chapter1 = new DefaultMutableTreeNode("Chapter 1");
        DefaultMutableTreeNode sub1 = new DefaultMutableTreeNode("1.1");
        DefaultMutableTreeNode sub2 = new DefaultMutableTreeNode("1.2");
        DefaultMutableTreeNode sub3 = new DefaultMutableTreeNode("1.3");
        DefaultMutableTreeNode sub31 = new DefaultMutableTreeNode("1.3.1");
        DefaultMutableTreeNode sub32 = new DefaultMutableTreeNode("1.3.2");

        root.add(chapter1);
        chapter1.add(sub1);
        chapter1.add(sub2);
        chapter1.add(sub3);
        sub3.add(sub31);
        sub3.add(sub32);

        final JTree tree = new JTree(root);
        expandTree(tree, false);

        JScrollPane pane = new JScrollPane(tree);
        pane.setPreferredSize(new Dimension(200, 200));

        JPanel buttonPanel = new JPanel(new BorderLayout());
        JButton expandAll = new JButton("Expand All");
        expandAll.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                expandTree(tree, true);
            }
        });

        JButton collapseAll = new JButton("Collapse All");
        collapseAll.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                expandTree(tree, false);
            }
        });

        buttonPanel.add(expandAll, BorderLayout.WEST);
        buttonPanel.add(collapseAll, BorderLayout.EAST);

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(pane, BorderLayout.CENTER);
        getContentPane().add(buttonPanel, BorderLayout.SOUTH);
    }

    private void expandTree(JTree tree, boolean expand) {
        TreeNode root = (TreeNode) tree.getModel().getRoot();
        expandAll(tree, new TreePath(root), expand);
    }

    private void expandAll(JTree tree, TreePath path, boolean expand) {
        TreeNode node = (TreeNode) path.getLastPathComponent();

        if (node.getChildCount() >= 0) {
            Enumeration enumeration = node.children();
            while (enumeration.hasMoreElements()) {
                TreeNode n = (TreeNode) enumeration.nextElement();
                TreePath p = path.pathByAddingChild(n);

                expandAll(tree, p, expand);
            }
        }

        if (expand) {
            tree.expandPath(path);
        } else {
            tree.collapsePath(path);
        }
    }

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

Preceptor

Answer 5

public void expandTree(){
    int row = 1;
    while (row++ < tree.getRowCount()){
        tree.expandRow(row);
    }

public void collapseTree(){
    int row = tree.getRowCount() - 1;
    while (row-- > 0){
        tree.collapseRow(row);
    }
}

Splanchnology

Please add some explanation to your code. Also, since this is an old question, check that your answer isn't already contained in another answer. – Sciomancy

@Alexander, in expandTree() method int row = 1; should be start from 0(int row = 0;) else the first node after Root node will not be expand. – Davedaveda