Main.java Source code

Introduction

Here is the source code for Main.java

Source

import java.awt.BorderLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingWorker;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeWillExpandListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.ExpandVetoException;
import javax.swing.tree.MutableTreeNode;
import javax.swing.tree.TreePath;

public class Main {
    public static void main(String[] args) throws Exception {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        MyTreeNode root = new MyTreeNode(1, 0);
        DefaultTreeModel model = new DefaultTreeModel(root);
        JProgressBar bar = new JProgressBar();
        PropertyChangeListener progressListener = new PropertyChangeListener() {
            @Override
            public void propertyChange(PropertyChangeEvent evt) {
                bar.setValue((Integer) evt.getNewValue());
            }
        };
        JTree tree = new JTree();
        tree.setShowsRootHandles(true);
        tree.addTreeWillExpandListener(new TreeWillExpandListener() {
            @Override
            public void treeWillExpand(TreeExpansionEvent event) throws ExpandVetoException {
                TreePath path = event.getPath();
                if (path.getLastPathComponent() instanceof MyTreeNode) {
                    MyTreeNode node = (MyTreeNode) path.getLastPathComponent();
                    node.loadChildren(model, progressListener);
                }
            }

            @Override
            public void treeWillCollapse(TreeExpansionEvent event) throws ExpandVetoException {

            }
        });
        tree.setModel(model);
        root.loadChildren(model, progressListener);
        frame.add(new JScrollPane(tree));
        frame.add(bar, BorderLayout.SOUTH);
        frame.pack();
        frame.setVisible(true);
    }
}

class MyTreeNode extends DefaultMutableTreeNode {
    boolean loaded = false;
    int depth;
    int index;

    public MyTreeNode(int index, int depth) {
        this.index = index;
        this.depth = depth;
        add(new DefaultMutableTreeNode("Loading...", false));
        setAllowsChildren(true);
        setUserObject("Index " + index + " at level " + depth);
    }

    private void setChildren(List<MyTreeNode> children) {
        removeAllChildren();
        setAllowsChildren(children.size() > 0);
        for (MutableTreeNode node : children) {
            add(node);
        }
        loaded = true;
    }

    @Override
    public boolean isLeaf() {
        return false;
    }

    public void loadChildren(final DefaultTreeModel model, final PropertyChangeListener progressListener) {
        if (loaded) {
            return;
        }
        SwingWorker<List<MyTreeNode>, Void> worker = new SwingWorker<List<MyTreeNode>, Void>() {
            @Override
            protected List<MyTreeNode> doInBackground() throws Exception {
                setProgress(0);
                List<MyTreeNode> children = new ArrayList<MyTreeNode>();
                if (depth < 5) {
                    for (int i = 0; i < 5; i++) {
                        Thread.sleep(300);
                        children.add(new MyTreeNode(i + 1, depth + 1));
                        setProgress((i + 1) * 20);
                    }
                } else {
                    Thread.sleep(1000);
                }
                setProgress(0);
                return children;
            }

            @Override
            protected void done() {
                try {
                    setChildren(get());
                    model.nodeStructureChanged(MyTreeNode.this);
                } catch (Exception e) {
                    e.printStackTrace();
                }
                super.done();
            }
        };
        if (progressListener != null) {
            worker.getPropertyChangeSupport().addPropertyChangeListener("progress", progressListener);
        }
        worker.execute();
    }
}