how to implement listener?

Question

Hello, I have some dynamic tree. And now I need to implement some functionality, that happend every time, when simply click on node. (I mean only one click on node, which "makes it blue")

*EDIT2: * I use beanTreeView and package openide

How to implement listener of this action?

EDIT - added pseudocode

public class MyNode extends AbstractNode{ //openide package
   private String name;

   public MyNode(String nameOfNode){
       super (new Children.LEAF);
       name = nameOfNode;
   }
   ....
   ....
}

public class IWantNameOfSelectedNode extends JPanel{   
    private JLabel jLnameOfNode;

   public IWantNameOfSelectedNode(){
       jLnameOfNode.setText("wiating for node selection");
   }

Now, I need put name of selected node to jLabel, and change it every time when selection of node changes.

Answer 1

I am assuming it is a Swing Tree. You could achieve this by using a CustomRenderer component or using a TreeSelectionListener interface.

This link has a tutorial for an advanced Example on how to alter the icons, backgrounds etc. What you need is a much simpler version than that.

The code you will be interested in is

public Component getTreeCellRendererComponent( JTree tree,
                    Object value, boolean bSelected, boolean bExpanded,
                            boolean bLeaf, int iRow, boolean bHasFocus )
    {
        // Find out which node we are rendering and get its text
        DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;
        String  labelText = (String)node.getUserObject();

        this.bSelected = bSelected;

        // Set the correct foreground color
        if( !bSelected )
            setForeground( Color.black );
        else
            setForeground( Color.white );
            ....
    }

Answer 2

Assuming you're using the Swing JTree class you should define a TreeSelectionListener and add it to the underlying TreeModel. If you wish to use ActionListener instead you'll need to write some adapter code to translate TreeSelectionEvents into ActionEvents (although this would actually be fairly pointless).

Example

/**
 * Adapter class responsible for translating TreeSelectionEvents into
 * ActionEvents.
 */
public class TreeSelectionAdapter implements TreeSelectionListener {
  private final AtomicInteger nextId = new AtomicInteger(0);
  // Prefer CopyOnWriteArrayList to avoid ConcurrentModificationException if an
  // ActionListener removes itself as a listener during notification.
  private final CopyOnWriteArrayList<ActionListener> listeners;

  public TreeSelectionAdapter() {
    this.listeners = new CopyOnWriteArrayList<ActionListener();
  }

  public void addActionListener(ActionListener l) {
    this.listeners.add(l);
  }

  public void removeActionListener(ActionListener l) {
    this.listeners.remove(l);
  }

  public void valueChanged(TreeSelectionEvent evt) {
    // Create new ActionEvent which corresponds to incoming TreeSelectionEvent
    // and notify registered ActionListeners.
    ActionEvent aEvt = new ActionEvent(evt.getSource(),
      nextId.getAndIncrement(), "selectionChanged");

    for (ActionListener listener : listeners) {
      listener.actionPerformed(listener);
    }
  }
}

TreeNode rootNode = createTreeModel(); // Create custom model
JTree tree = new JTree(rootNode); // Install model into JTree.

// Add adapter listener to underlying selection model.
tree.getSelectionModel().addTreeSelectionListener(adapter);

// Register ActionListener with adapter listener.
adapter.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent evt) {
    System.err.println("Selection has changed in some way!");
  }
});