Implementing a dynamic Scrollable JPopupMenu

Question

Hi,
I wanna make a scrollable JPopupMenu. What I am looking for is I am making a custom popup Menu which extends JPopupMenu. I would be overriding the add method.
I dont want to add a list or a combo box to my JPopupMenu. I want to change the layout itself .. i.e. there is a function in the Container.class which gets called when we try to add a menuitem dynamically to the JPopupMenu
Function Name:
protected void addImpl(Component comp, Object constraints, int index)Snippet which i am looking in the function
if (layoutMgr instanceof LayoutManager2) {
((LayoutManager2)layoutMgr).addLayoutComponent(comp, constraints);
          }Is there a way while addiing menu items dynamically that I can set the layout to scrollable and hence the menuitems when added are in a scrollpane automatically.. Hence I what i get also is a Scrollable JPopupMenu

Answer 1

well, this is implementation of PopupMenu with scroll
import java.awt.Component;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.JScrollPane;
import javax.swing.JSeparator;
public class ScrollPopupMenu extends JPopupMenu {
     private static final long serialVersionUID = 1L;
     private JPanel panelMenus = null;
     private JScrollPane scroll = null;
     public ScrollPopupMenu(GraphicsConfiguration gc) {
          super();
          scroll = new JScrollPane();
          panelMenus = new JPanel();
          panelMenus.setLayout(new GridLayout(0,1));
          scroll.setViewportView(panelMenus);
          scroll.setBorder(null);
          scroll.setMaximumSize(new Dimension(scroll.getMaximumSize().width,
                    this.getToolkit().getScreenSize().height -
                    this.getToolkit().getScreenInsets(gc).top -
                    this.getToolkit().getScreenInsets(gc).bottom - 4));
          super.add(scroll);
     public void show(Component invoker, int x, int y) {
          this.pack();
          panelMenus.validate();
          int maxsize = scroll.getMaximumSize().height;
          int realsize = panelMenus.getPreferredSize().height;
          int sizescroll = 0;
          if (maxsize < realsize) {
               sizescroll = scroll.getVerticalScrollBar().getPreferredSize().width;
          scroll.setPreferredSize(new Dimension(
                    scroll.getPreferredSize().width + sizescroll,
                    scroll.getPreferredSize().height));
          super.show(invoker, x, y);
     public void add(JButton menuItem) {
          panelMenus.add(menuItem);
     public void addSeparator() {
          panelMenus.add(new JSeparator());
}It is very basic, but this to help you, If you want to test, you compile this class:
import javax.swing.SwingUtilities;
import javax.swing.JPanel;
import javax.swing.JFrame;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JTextField;
import javax.swing.JLabel;
public class FramePopupMenu extends JFrame {
     private static final long serialVersionUID = 1L;
     private JPanel jContentPane = null;
     private JButton btnPopup = null;
     private JTextField txtNumElem = null;
     private JLabel lblNumElem = null;
     private JButton getBtnPopup() {
          if (btnPopup == null) {
               btnPopup = new JButton();
               btnPopup.setText("Ver men� popup");
               btnPopup.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                         ScrollPopupMenu mnu = new ScrollPopupMenu(FramePopupMenu.this.getGraphicsConfiguration());
                         int n = Integer.parseInt(getTxtNumElem().getText());
                         for (int i=0;i<n;i++)
                              mnu.add(new JButton("Men� " + (i+1)));
                         mnu.show(btnPopup, btnPopup.getWidth(), 0);
          return btnPopup;
     private JTextField getTxtNumElem() {
          if (txtNumElem == null) {
               txtNumElem = new JTextField();
               txtNumElem.setColumns(3);
               txtNumElem.setText("60");
          return txtNumElem;
     public static void main(String[] args) {
          SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    FramePopupMenu thisClass = new FramePopupMenu();
                    thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    thisClass.setVisible(true);
     public FramePopupMenu() {
          super();
          initialize();
     private void initialize() {
          this.setSize(274, 109);
          this.setContentPane(getJContentPane());
          this.setTitle("Scroll en un men� popup");
     private JPanel getJContentPane() {
          if (jContentPane == null) {
               lblNumElem = new JLabel();
               lblNumElem.setText("N�mero de elementos del Men�");
               FlowLayout flowLayout = new FlowLayout();
               flowLayout.setHgap(8);
               flowLayout.setVgap(8);
               jContentPane = new JPanel();
               jContentPane.setLayout(flowLayout);
               jContentPane.add(getBtnPopup(), null);
               jContentPane.add(lblNumElem, null);
               jContentPane.add(getTxtNumElem(), null);
          return jContentPane;
}