Making an existing component to wear a scrollpane

Question

I don't want to have a scrollpane. I just want TheComponent that wears a scrollpane. For example, I want to put a scrollpane on the editor component of a combobox. Or more generically and as a related question, how could we write a class extending C, of which object is C in OOP parlance, that has a scrollpane put on it?
Is it an impossible dream in current Swing?

Answer 1

you should be able to create a custom editor that uses a JScrollPane containing a JTextFieldAnd I'm afraid we are not. Here's another failure:
import javax.swing.plaf.metal.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ScrollingComboBoxEditor extends MetalComboBoxEditor{
  JScrollPane jsc;
  JTextField jtf;
  public ScrollingComboBoxEditor(JScrollPane js){
    jsc = js;
    jtf = (JTextField)(js.getViewport().getView());
  public JTextField createEditorComponent(){
    return jtf;
  public Component getEditorComponent(){
    return jsc;
  public Object getItem(){
    return jtf.getText();
  public void selectAll(){
    jtf.selectAll();
  public void setItem(Object anObject){
    jtf.setText((String)anObject);
  public static void main(String[] args){
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JTextField jtf = new JTextField(20);
    JScrollPane jsp = new JScrollPane
     (jtf,  JScrollPane.VERTICAL_SCROLLBAR_NEVER,
      JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    final JComboBox jcb
      = new JComboBox(new String[]{"alpha", "beta", "gamma"});
    jcb.setEditor(new ScrollingComboBoxEditor(jsp));
    jcb.setEditable(true);
    jcb.configureEditor(jcb.getEditor(),
        "alonglonglonglonglonglonglonglonglonglonglongonelinetext");
    jcb.addActionListener(new ActionListener(){
      public void actionPerformed(ActionEvent e){
        String newSelection = (String)jcb.getSelectedItem();
        jcb.addItem(newSelection);
    frame.getContentPane().add(jcb, java.awt.BorderLayout.NORTH);
    frame.pack();
    frame.setVisible(true);
}