JTree rendering with JCheckBox nodes

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…

Accepted Answer

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());
        Tr…

JTree rendering with JCheckBox nodes

Solution

Problem