Java SE (Java Platform, Standard Edition)

Hi,

I have created a simple Swing application, which consists of some JComponent (e.g., a table, replaced by a JPanel in this demo), and of a toolbar above the component. The component can add/remove additional toolbars into the toolbar panel using two buttons. The toolbar pane is contained in a JScrollPane, so that you can add many toolbars and scroll to them. For better visibility, the toolbar pane has a blue background.

I have the following problem. If I set the ScrollPane's scrollbar policy to HORIZONTAL_SCROLLBAR_ALWAYS, all is well, BUT the scrollbar consumes space even if it is not needed. However, if I set the policy to HORIZONTAL_SCROLLBAR_AS_NEEDED, the ScrollPane begins to act strangely. If I add the first toolbar, there is too much space (as if there was a scrollbar). If I resize the component so that the scrollbar is shown, the scrollpane resizes incorrectly and the scroll bar spans over the toolbar.

The sample code follows. I tried some black magic (validating/revalidating, setting maximum, minimum, preferred sizes, etc.), but nothing helped. What am I doing wrong?

Thanks for any help!

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;

public class Tester2 extends JPanel {

    private static final long serialVersionUID = 1L;

    public Tester2() {
        JNotWorkingCrap crap = new JNotWorkingCrap();
        add(crap);
    }

    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        Tester2 newContentPane = new Tester2();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

    public static class JNotWorkingCrap extends JPanel {

        /** panel with toolbars */
        private JPanel toolbarPane;
        /** scroll pane for the toolbar pane */
        private JScrollPane toolbarSp;
        /** central panel with the buttons*/
        private JPanel centralPanel;
        /** buttons for adding/removing a toolbar */
        private JButton addToolbarBtn;
        private JButton removeToolbarBtn;

        /** counter indicating number of toolbars */
        private static int toolbarCnt = 0;

        public JNotWorkingCrap() {
            initComponents();
            initLayout();
        }

        private void initComponents() {
            centralPanel = new JPanel();
            toolbarPane = new JPanel();
            toolbarSp = new JScrollPane(toolbarPane);

            addToolbarBtn = new JButton(new AbstractAction("Add toolbar") {

                @Override
                public void actionPerformed(ActionEvent e) {
                    // create a new "toolbar" 
                    JPanel newToolbar = new JPanel();
                    newToolbar.add(new JLabel("Toolbar "+toolbarCnt));
                    // with a fixed size
                    newToolbar.setPreferredSize(new Dimension(150, 50));
                    newToolbar.setMinimumSize(new Dimension(150, 50));
                    newToolbar.setMaximumSize(new Dimension(150, 50));
                    newToolbar.setSize(new Dimension(150, 50));
                    newToolbar.setBorder(BorderFactory.createTitledBorder("Toolbar " + toolbarCnt));

                    // add the "toolbar" to the toolbar pane
                    toolbarPane.add(newToolbar);

                    // revalidate/repaint
                    toolbarPane.revalidate();
                    revalidate();
                    revalidate();

                    // increment the counter
                    toolbarCnt++;
                }
            });

            removeToolbarBtn = new JButton(new AbstractAction("Remove toolbar") {

                @Override
                public void actionPerformed(ActionEvent e) {
                    // remove the toolbar from the toolbar pane
                    toolbarPane.remove(toolbarPane.getComponentCount()-1);

                    // revalidate/repaint
                    toolbarPane.revalidate();
                    revalidate();
                    toolbarPane.repaint();

                    // decrement the counter
                    toolbarCnt--;
                }
            });

        }

        /**
         * Lay out the components.
         */
        private void initLayout() {
            setLayout(new BorderLayout(0, 0));
            setPreferredSize(new Dimension(600, 300));

            centralPanel.add(addToolbarBtn);
            centralPanel.add(removeToolbarBtn);

            toolbarPane.setLayout(new BoxLayout(toolbarPane, BoxLayout.X_AXIS));
            toolbarPane.setOpaque(true);
            toolbarPane.setBackground(Color.BLUE);

            toolbarSp.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
            //toolbarSp.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
            toolbarSp.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_NEVER);

            add(toolbarSp, BorderLayout.NORTH);
            add(centralPanel, BorderLayout.CENTER);
        }

    }

}

Edited by: DavidStefka on Feb 5, 2010 7:53 AM