Question

I am attempting to modify the standard Swing JTree to intermingle nodes with and without checkboxes. This is an example:

When I attempt to check/uncheck one of the checkboxes (the ‘User 01’ node in this example), the tree loses nodes:

I my code is an adaptation of this example: http://forums.sun.com/thread.jspa?threadID=5321084&start=13.

Instead of embedding a JCheckBox in a DefaultMutableTreeNode like this:

new DefaultMutableTreeNode(new CheckBoxNode("Accessibility", true));

I thought it made more sense to create a model node that derived from the DefaultMutableTreeNode, which I call JTreeNode. This class automatically sets the DefaultMutableTreeNode’s UserObject to a JCheckBox. The class’ ShowCheckBox property is used by the TreeCellRenderer to determine if the JCheckBox or DefaultTreeCellRenderer is used. The JTreeNode is used like this:

    JTreeNode user01 = new JTreeNode("User 01");
    user01.setShowCheckBox(true);
    user01.setSelected(true);

I believe the problem is with the class that implements the TreeCellEditor, specifically in the getCellEditorValue() or getTreeCellEditorComponent() methods. I suspect the issue has something to with the getCellEditorValue() returning a derivative of the DefaultMutableTreeNode, rather than a simpler model instance.

public Object getCellEditorValue() {

    JCheckBox checkBox = renderer.getCheckBoxRenderer();

    JTreeNode node = new JTreeNode(checkBox.getText());
    node.setShowCheckBox(true);
    node.setSelected(checkBox.isSelected());
    return node;

}

public Component getTreeCellEditorComponent(JTree tree, Object value, boolean isSelected, boolean expanded, boolean leaf, int row) {

    Component editor = renderer.getTreeCellRendererComponent(tree, value, true, expanded, leaf, row, true);

    // editor always selected / focused
    ItemListener itemListener = new ItemListener() {
        public void itemStateChanged(ItemEvent itemEvent) {
            if (stopCellEditing()) {
                fireEditingStopped();
            }
        }
    };

    if (editor instanceof JCheckBox) {
        ((JCheckBox) editor).addItemListener(itemListener);
    }

    return editor;

}

Here is the TreeCellRender’s getTreeCellRendererComponent() method:

public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) {

    Component component;

    //if object being passed for rendering is a JTreeNode that should show a JCheckBox, attempt to render it so
    if (((JTreeNode) value).getShowCheckBox()) {

        String stringValue = tree.convertValueToText(value, selected, expanded, leaf, row, false);

        //set default JCheckBox rendering
        checkBoxRenderer.setText(stringValue);
        checkBoxRenderer.setSelected(false);    //not checked
        checkBoxRenderer.setEnabled(tree.isEnabled());

        if (selected) {
            //removed colorization
            //checkBoxRenderer.setForeground(selectionForeground);
            //checkBoxRenderer.setBackground(selectionBackground);
        }
        else {
            checkBoxRenderer.setForeground(textForeground);
            checkBoxRenderer.setBackground(textBackground);
        }

        //DefaultMutableTreeNode
        if ((value != null) && (value instanceof JTreeNode)) {

            //userObject should be a JTreeNode instance
            //DefaultMutableTreeNode
            //Object userObject = ((JTreeNode) value).getUserObject();

            //if it is
            //if (userObject instanceof JTreeNode) {
                //cast as a JTreeNode
                //JTreeNode node = (JTreeNode) userObject;
                JTreeNode node = (JTreeNode) value;

                //set JCheckBox settings to match JTreeNode's settings
                checkBoxRenderer.setText(node.getText());
                checkBoxRenderer.setSelected(node.isSelected());

            //}

        }

        component = checkBoxRenderer;

    }

    //if not, render the default
    else {

        component = defaultRenderer.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus);

    }

    return component;

}

Any thoughts are greatly appreciated.

Answer 1

I was able to solve the problem.

I created a model class (TreeNodeModel) to hold the relevant node data: key, value, hasCheckBox, isSelected:

public class TreeNodeModel {

    int key;
    String value;
    boolean isSelected=false;
    boolean hasCheckBox=false;

    public TreeNodeModel() {
    }
    public TreeNodeModel(int key, String value) {
        this.key=key;
        this.value = value;
    }
    public TreeNodeModel(int key, String value, boolean hasCheckBox) {
        this.key=key;
        this.value = value;
        this.hasCheckBox = hasCheckBox;
    }
    public TreeNodeModel(int key, String value, boolean hasCheckBox, boolean isSelected) {
        this.key=key;
        this.value = value;
        this.hasCheckBox=hasCheckBox;
        this.isSelected = isSelected;
    }

    public boolean isSelected() {
        return this.isSelected;
    }
    public void setSelected(boolean newValue) {
        this.isSelected = newValue;
    }

    public boolean hasCheckBox() {
        return this.hasCheckBox;
    }
    public void setCheckBox(boolean newValue) {
        this.hasCheckBox=newValue;
    }

    public int getKey() {
        return this.key;
    }
    public void setKey(int newValue) {
        this.key = newValue;
    }

    public String getValue() {
        return this.value;
    }
    public void setValue(String newValue) {
        this.value = newValue;
    }

    @Override
    public String toString() {
        return getClass().getName() + "[" + this.value + "/" + this.isSelected + "]";
//        return this.text;
    }

}

I created an implementation of the TreeCellEditor interface:

public class TreeNodeEditor  extends AbstractCellEditor implements TreeCellEditor {

    private JTree tree;
    private TreeNodeModel editedModel = null;

    TreeNodeRenderer renderer = new TreeNodeRenderer();

    public TreeNodeEditor(JTree tree) {
        this.tree=tree;
    }

    @Override
    public boolean isCellEditable(EventObject event) {

        boolean editable=false;

        if (event instanceof MouseEvent) {

            MouseEvent mouseEvent = (MouseEvent) event;
            TreePath path = tree.getPathForLocation(mouseEvent.getX(),mouseEvent.getY());

            if (path != null) {

                Object node = path.getLastPathComponent();

                if ((node != null) && (node instanceof DefaultMutableTreeNode)) {

                    DefaultMutableTreeNode editedNode = (DefaultMutableTreeNode) node;
                    TreeNodeModel model = (TreeNodeModel) editedNode.getUserObject();
                    editable = model.hasCheckBox;

                }   //if (node)
            }   //if (path)
        }   //if (MouseEvent)

        return editable;

    }

    public Object getCellEditorValue() {

        JCheckBox checkbox = renderer.getCheckBoxRenderer();

        TreeNodeModel model = new TreeNodeModel(editedModel.getKey(), checkbox.getText(), true, checkbox.isSelected());
        return model;

    }

    public Component getTreeCellEditorComponent(JTree tree, Object value, boolean isSelected, boolean expanded, boolean leaf, int row) {

        if (((DefaultMutableTreeNode) value).getUserObject() instanceof TreeNodeModel) {
            editedModel = (TreeNodeModel) ((DefaultMutableTreeNode) value).getUserObject();
        }

        Component editor = renderer.getTreeCellRendererComponent(tree, value, true, expanded, leaf, row, true);

        // editor always selected / focused
        ItemListener itemListener = new ItemListener() {
            public void itemStateChanged(ItemEvent itemEvent) {
                if (stopCellEditing())
                    fireEditingStopped();
            }
        };

        if (editor instanceof JCheckBox) {
            ((JCheckBox) editor).addItemListener(itemListener);
        }

        return editor;
    }

}

The key was capturing the model in the getTreeCellEditorComponent() method and using its Key in the getCellEditorValue() method.

Building the tree was easy:

DefaultMutableTreeNode server = new DefaultMutableTreeNode(new TreeNodeModel(0,"Server 01", false));

DefaultMutableTreeNode userFolder = new DefaultMutableTreeNode(new TreeNodeModel(1, "User Folders", false));
server.add(userFolder);

DefaultMutableTreeNode user01 =  new DefaultMutableTreeNode(new TreeNodeModel(2, "User 01", true, true));
userFolder.add(user01);

DefaultMutableTreeNode clientA = new DefaultMutableTreeNode(new TreeNodeModel(3, "Client A", true, true));
user01.add(clientA);

DefaultMutableTreeNode clientB = new DefaultMutableTreeNode(new TreeNodeModel(4, "Client B", true, true));
user01.add(clientB);

DefaultMutableTreeNode publicFolder = new DefaultMutableTreeNode(new TreeNodeModel(5, "Public Folders", false));
server.add(publicFolder);

DefaultMutableTreeNode clientC = new DefaultMutableTreeNode(new TreeNodeModel(6, "Client C", true));
publicFolder.add(clientC);
        Tree_Nodes.setCellRenderer(new TreeNodeRenderer());
        Tree_Nodes.setCellEditor(new TreeNodeEditor(Tree_Nodes));
Tree_Nodes.setModel(new DefaultTreeModel(server);

Finally, determining which nodes where checked was a matter of examining the model’s node collection (via a button):

private Map<Integer, String> checked = new HashMap<Integer, String>();

private void Button_CheckedActionPerformed(java.awt.event.ActionEvent evt) {

    DefaultTableModel tableModel = ((DefaultTableModel) Table_Nodes.getModel());
    tableModel.getDataVector().removeAllElements();
    tableModel.fireTableDataChanged();

    checked.clear();

    DefaultTreeModel treeModel = (DefaultTreeModel) Tree_Nodes.getModel();
    DefaultMutableTreeNode root = (DefaultMutableTreeNode) treeModel.getRoot();

    getChildNodes(root);

    for (Iterator it=checked.entrySet().iterator(); it.hasNext(); ) {
        Map.Entry entry = (Map.Entry)it.next();
        tableModel.addRow(new Object[] {entry.getKey(), entry.getValue()});
    }

    Button_Checked.requestFocus();


}

private void getChildNodes(DefaultMutableTreeNode parentNode) {

    for (Enumeration e=parentNode.children(); e.hasMoreElements();) {

        DefaultMutableTreeNode childNode = (DefaultMutableTreeNode) e.nextElement();
        TreeNodeModel model = (TreeNodeModel) childNode.getUserObject();

        if (model.hasCheckBox && model.isSelected()) {
            checked.put(model.getKey(), model.getValue());
        }

        //recurse
        if (childNode.getChildCount()>0) getChildNodes(childNode);

    }

}