Using Swing UI components for the visual representation of a node can be accomplished by providing an implementation for interface NodeCellRenderer. This interface behaves similar to Java Swing interfaces such as TableCellRenderer or TreeCellRenderer, and serves as a callback for the logic that is responsible for painting the node realizer. Following is the callback method defined by interface NodeCellRenderer:

JComponent getNodeCellRendererComponent(Graph2DView view, NodeRealizer context,
                                        Object value, boolean isSelected)

Class NodeCellRendererPainter provides support for rendering Swing UI components with GenericNodeRealizer. It is an implementation for interface GenericNodeRealizer.Painter which is responsible for painting generic node realizers. A NodeCellRendererPainter instance can be instantiated using a NodeCellRenderer implementation and be added to a GenericNodeRealizer configuration. The given NodeCellRenderer implementation is then invoked to return the JComponent that serves as the visual representation for a node.

Defining a GenericNodeRealizer configuration that uses NodeCellRendererPainter is outlined in Example 6.29, “Defining a GenericNodeRealizer configuration that supports rendering of UI components”. Tutorial demo application SwingRendererDemo.java shows how to define a corresponding NodeCellRenderer that returns a JComponent.

void createJTextFieldNodeRealizer()
{
  // Create a customized NodeCellRenderer instance that defines the visual 
  // representation of a node. 
  NodeCellRenderer myNCR = new MyJTextFieldNodeCellRenderer();
  
  // Define a GenericNodeRealizer configuration that uses 'myNCR' as a callback 
  // for class NodeCellRendererPainter. 
  // This class provides support for rendering Swing UI components. 
  GenericNodeRealizer.Factory factory = GenericNodeRealizer.getFactory();
  Map map = factory.createDefaultConfigurationMap();
  map.put(
    GenericNodeRealizer.Painter.class, 
    new NodeCellRendererPainter(myNCR, NodeCellRendererPainter.USER_DATA_MAP));
  map.put(
    GenericNodeRealizer.UserDataHandler.class, 
    new SimpleUserDataHandler(SimpleUserDataHandler.REFERENCE_ON_FAILURE));
  
  // Register the configuration using the given name. 
  factory.addConfiguration("JTextField", map);
}

The UI components rendered in the view provide the full range of mouse-based user interaction that is also supported for "ordinary" nodes, i.e., they can be selected, moved around, or scaled using their resize knobs, for example. They are also subject to changes of the viewport such as zooming in or out.

In addition to using Swing UI components for the visual representation of nodes by means of a NodeCellRenderer implementation (as shown above), the components can also be used as proper editors. As a special feature, these Swing-based editors remain editable even when zoomed. Figure 6.38, “Editing a zoomed JComponent” shows a zoomed-in JTextField before and after editing its value.

Figure 6.38. Editing a zoomed JComponent

Enhancing a node realizer that renders a JComponent with editor functionality can be accomplished by providing an implementation for interface NodeCellEditor. The section Node-Related Editing Capabilities describes this interface and its role for user interaction with UI components.

Class CellEditorMode is the view mode that knows all nodes that have a Swing-based editor associated. It recognizes whenever a user attempts to use such an editor and initiates node editing. See the section called “Class CellEditorMode” for a detailed description of this view mode.

The tutorial demo application SwingRendererDemo.java shows how Java Swing UI components can be used for both rendering the visual representation of nodes and additionally providing editors for node-related data.