Re: JTree within JScrollPane: Update visible rect on model change events

From:

"tomaszewski.p" <ksswzza@gmail.com>

Newsgroups:

comp.lang.java.gui

Date:

Thu, 28 Aug 2008 14:43:15 +0200

Message-ID:

<g96633$b4h$1@news.interia.pl>

"JSchneider" <johannes@familieschneider.info> wrote in message
news:0a56d7bd-4911-480e-82ea-413d2adf8764@c58g2000hsc.googlegroups.com...

Hi,

I have the following requirement:

I have a JTree placed within a JScrollPane. The model of the JTree is
now updated every other second. But the additional entries are added
at the top of the Model (index is nearly always 0).
This is a requirement and can't be changed...

[...]

Now the problem:
If the user has scrolled to the bottom (he wants to see the youngest
entries) the visible entries change every time an additional row is
added at the top (old mail has been added).

[...]

ScrollRectToVisble causes a
repaint with the old visible rect. Therefore the tree is
"jumping" (paints one time with the "wrong" visible rect).

[...]

Try this:

import java.util.Enumeration;
import java.util.List;
import java.util.LinkedList;

import java.awt.BorderLayout;

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;

import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeNode;

import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeModelEvent;

public class JTreeRefreshTest {

    static class NodeElement {
        private String message;

        public NodeElement(String message) {
            this.message = message;
        }

        @Override
        public String toString() {
            return message;
        }
    }

    static class TestTreeModel extends DefaultTreeModel {
           public TestTreeModel(TreeNode root) {
               super(root);
           }

           public void addNode(DefaultMutableTreeNode parent,
DefaultMutableTreeNode child)
           {
               parent.insert(child, 0);
               final int childIndex = parent.getIndex(child);
               fireTreeNodesInserted(parent, parent.getPath(), new int[]
{childIndex}, new Object[] {child});
           }
    }

    static class TestPanel extends JPanel {
        private DefaultMutableTreeNode rootNode;
        private TestTreeModel treeModel;

        public TestPanel() {
            super();
            rootNode = new DefaultMutableTreeNode(new NodeElement("Root"));
            for (int idx = 0; idx < 100; idx++) {
                rootNode.add(new DefaultMutableTreeNode(new
NodeElement("Child " + idx)));
            }
            treeModel = new TestTreeModel(rootNode);

            final JTree tree = new JTree(treeModel);
            final JScrollPane scroll = new JScrollPane();
            scroll.getViewport().add(tree);

            setLayout(new BorderLayout());
            add(scroll, BorderLayout.CENTER);

            tree.addKeyListener(new KeyAdapter() {
                @Override
                public void keyReleased(KeyEvent event) {
                    if (event.getKeyCode() == KeyEvent.VK_1) {
                        final DefaultMutableTreeNode newNode = new
DefaultMutableTreeNode(new NodeElement("New Node"));
                        treeModel.addNode(rootNode, newNode);
                    }
                }
            });
            treeModel.addTreeModelListener(new TreeModelListener() {
                @Override
                public void treeNodesChanged(TreeModelEvent event) {
                }

                @Override
                public void treeNodesInserted(TreeModelEvent event) {
                    tree.scrollPathToVisible(event.getTreePath());
                }

                @Override
                public void treeNodesRemoved(TreeModelEvent event) {
                }

                @Override
                public void treeStructureChanged(TreeModelEvent event) {
                }
            });
        }
    }

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(new TestPanel(), BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

}

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