JScrollPane Frustrations

[Chris Waguespack]

Ok, I'm trying to create a JScrollPane that will hold custom visual classes. The way I'm currently doing it is

/**
 * This method initializes changesScrollPane
 * 
 * @return javax.swing.JScrollPane
 */
private JScrollPane getChangesScrollPane() {
if (changesScrollPane == null) {
changesScrollPane = new JScrollPane();
changesScrollPane.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.RAISED));
changesScrollPane.setViewportView(getChangesPanel());
}
return changesScrollPane;
}

/**
 * This method initializes changesPanel
 * 
 * @return javax.swing.JPanel
 */
private JPanel getChangesPanel() {
if (changesPanel== null) {
changesPanel= new JPanel();
changesPanel.setLayout(new BoxLayout(getChangesPanel(), BoxLayout.Y_AXIS));
}
return changesPanel;
}

then when a button is pressed

changesPanel.add(new RandomTestBar());
changesPanel.validate();

What I would like to have happen is when I press the button, it will add an instance of the RandomTestBar to the changesPanel, and since the RandomTestBar is bigger than the space I've given to the scroll pane, I would want the scroll bar to appear. Right now, the RandomTestBar is just fitting itself inside the scroll pane. Is this a scroll pane problem or a layout problem, and how would you suggest a fix for this.

Thanks much,
Chris

Edit: What I want it to look like

[ February 07, 2008: Message edited by: Chris Waguespack ]

[Brian Cole]

I once had to do something similar, and I ended up using a JList with a custom renderer. One motivation for this is I wanted to be able to drag/drop the panels, so it was handy to use JList's TransferHandler support. But also JList was built to be placed in a JScrollPane and for items to be added/deleted dynamically.

It should be possible to get your approach working (try calling revalidate() not only on the changesPanel but also on the changesScrollPane and see if that helps) but if your RandomTestBar objects are simple enough you might want to consider using a JList.

[Brian Cole]

To show what I mean, here's some code that approximates the look of your diagram.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.Border;
 
/**
 *  use a JList with custom renderer to show a scrolling list of bar-shaped widgets
 *  
 *  @author Brian Cole
 */
public class Waguespack {
 
public static void main(String[] argv) {
final DefaultListModel listModel = new DefaultListModel();
JList list = new JList(listModel);
list.setCellRenderer(new TestBarRenderer());
 
JScrollPane scrollPane = new JScrollPane(list);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
 
// add some initial random test bars to the JList
for (int j=0; j < 3; j+=1) {
listModel.addElement(new RandomTestBar());
}
 
JPanel buttonPanel = new JPanel();
JButton b = new JButton("add a random test bar");
buttonPanel.add(b);
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
listModel.addElement(new RandomTestBar());
}
});
 
JPanel contentPane = new JPanel(new BorderLayout());
contentPane.add(buttonPanel, BorderLayout.NORTH);
contentPane.add(scrollPane, BorderLayout.CENTER);
contentPane.setBackground(new Color(252, 253, 162)); // pale yellow
contentPane.setOpaque(true);
contentPane.setBorder(BorderFactory.createEmptyBorder(0, 10, 30, 10));
buttonPanel.setOpaque(false);
buttonPanel.setBorder(BorderFactory.createEmptyBorder(16, 0, 16, 0));
 
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(contentPane);
f.setSize(652, 504);
f.setVisible(true);
}


/** 
 * test class that holds five random values -- exists just so TestBarRenderer can render it
 */
public static class RandomTestBar {
private int[] a = { rand(), rand(), rand(), rand(), rand() };
 
public int getValue(int index) {
return a[index];
}
private static int rand() {
return Math.round(100*(float)Math.random());
}
}
 
/**
 *  a fancy list cell renderer to display a RandomTestBar's values
 *  
 *  @author Brian Cole
 */
public static class TestBarRenderer extends JPanel implements ListCellRenderer {
 
private static final Dimension DIM = new Dimension(700, 100);
private static Border BORDER = BorderFactory.createCompoundBorder(
BorderFactory.createEmptyBorder(2, 4, 2, 4), BorderFactory.createCompoundBorder(
BorderFactory.createLineBorder(new Color(188, 143, 143), 2), // soft brown
BorderFactory.createEmptyBorder(3, 5, 3, 5)));
 
JLabel northwest = new JLabel();
JLabel northeast = new JLabel();
JLabel southwest = new JLabel();
JLabel southeast = new JLabel();
JLabel center = new JLabel("", null, JLabel.CENTER);
 
public TestBarRenderer() {
super(new BorderLayout());
setBorder(BORDER);
setPreferredSize(DIM);
center.setFont(center.getFont().deriveFont(32f));
 
JPanel north = new JPanel(new BorderLayout());
JPanel south = new JPanel(new BorderLayout());
add(north, BorderLayout.NORTH);
add(south, BorderLayout.SOUTH);
add(center, BorderLayout.CENTER);
north.add(northwest, BorderLayout.WEST);
north.add(northeast, BorderLayout.EAST);
south.add(southwest, BorderLayout.WEST);
south.add(southeast, BorderLayout.EAST);
 
setOpaque(true);
north.setOpaque(false);
south.setOpaque(false);
northwest.setOpaque(false);
northeast.setOpaque(false);
southwest.setOpaque(false);
southeast.setOpaque(false);
center.setOpaque(false);
}
 
public Component getListCellRendererComponent(JList list, Object value,
int index, boolean isSelected, boolean cellHasFocus) {
if (value instanceof RandomTestBar) {
RandomTestBar bar = (RandomTestBar)value;
center.setText( Integer.toString(bar.getValue(0)) );
northwest.setText( Integer.toString(bar.getValue(1)) );
northeast.setText( Integer.toString(bar.getValue(2)) );
southwest.setText( Integer.toString(bar.getValue(3)) );
southeast.setText( Integer.toString(bar.getValue(4)) );
} else {
// shouldn't happen, but might as well be polite
center.setText(String.valueOf(value));
northwest.setText("");
northeast.setText("");
southwest.setText("");
southeast.setText("");
}
 
Color foreg;
if (isSelected) {
setBackground(list.getSelectionBackground());
foreg = list.getSelectionForeground();
}
else {
setBackground(list.getBackground());
foreg = list.getForeground();
}
center.setForeground(foreg);
northwest.setForeground(foreg);
northeast.setForeground(foreg);
southwest.setForeground(foreg);
southeast.setForeground(foreg);
 
return this;
}
 
// override some methods to no-ops for performance
public void revalidate() { }
public void repaint() { }
public void repaint(Rectangle r) { }
public void repaint(long tm, int x, int y, int width, int height) { }
public void firePropertyChange(String propertyName, byte oldValue, byte newValue) { }
public void firePropertyChange(String propertyName, char oldValue, char newValue) { }
public void firePropertyChange(String propertyName, short oldValue, short newValue) { }
public void firePropertyChange(String propertyName, int oldValue, int newValue) { }
public void firePropertyChange(String propertyName, long oldValue, long newValue) { }
public void firePropertyChange(String propertyName, float oldValue, float newValue) { }
public void firePropertyChange(String propertyName, double oldValue, double newValue) { }
public void firePropertyChange(String propertyName, boolean oldValue, boolean newValue) { }
protected void firePropertyChange(String propertyName, Object oldValue, Object newValue) { }
// don't override validate() -- need that to perform layout
// don't override invalidate() -- need that to render after size change
}
 
}

[Chris Waguespack]

Ah, ok. That fixes part of my issues. Thanks. So, if I wanted to add a button, or other dynamic component to the bar, would I need to use a table with a custom editor instead? If so, I've tried that but can't seem to get a grasp on the correct way to implement it. Any advise or examples that may be useful?

Thanks,
Chris

[Brian Cole]

Originally posted by Chris Waguespack:
So, if I wanted to add a button, or other dynamic component to the bar, would I need to use a table with a custom editor instead?

JList doesn't have editors at all so, yes, you could use a one-column JTable instead and set a custom cell editor if you want to go with an approach like this. If there components that the user needs to manipulate (perhaps even a single button) I'm not sure this approach is worth it.

Are these test bars related to the panels in this older post of yours? If so I think my advice in that thread is better than my advice in this thread.

[Chris Waguespack]

Ah! I completely forgot about that.
Yes, that one does great, but I need the custom bars to stay a fixed size, so that they will not try to take up the entire viewing area. Setting the minimum/preferred size of the panels doesn't seem to help. Thanks for all of your help and patience.

-Chris

[Chris Waguespack]

Ok, I got it this far, but the scroll bars won't update until I resize the window. How do I fix this?

import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.border.EtchedBorder;
 
public class WaguespackTest extends JFrame implements ActionListener {

private static final longserialVersionUID= 1L;

/**
 * @param args
 */
public static void main(final String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
final WaguespackTest thisClass = new WaguespackTest();
thisClass.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
thisClass.setVisible(true);
}
});
}

private JPaneljContentPane= null;
private JScrollPanechangesScrollPane= null;
private JPanelchangesScrollPanel= null;

private JButtonjButton= null;

/**
 * This is the default constructor
 */
public WaguespackTest() {
super();
initialize();
}

@Override
public void actionPerformed(final ActionEvent e) {
if ((e.getSource() == jButton)) {
for (int i = 0; i < changesScrollPanel.getComponentCount(); ++i) {
final GridBagConstraints gridBagConstraints = new GridBagConstraints();
gridBagConstraints.anchor = GridBagConstraints.NORTHWEST;
gridBagConstraints.fill = GridBagConstraints.NONE;
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = i;
gridBagConstraints.weightx = 1.0;
gridBagConstraints.weighty = 0.0;

changesScrollPanel.remove(changesScrollPanel.getComponents()[i]);
changesScrollPanel.add(new JButton(""
+ i),
gridBagConstraints,
i);
}
final GridBagConstraints gridBagConstraints = new GridBagConstraints();
gridBagConstraints.anchor = GridBagConstraints.NORTHWEST;
gridBagConstraints.fill = GridBagConstraints.NONE;
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = changesScrollPanel.getComponentCount();
gridBagConstraints.weightx = 1.0;
gridBagConstraints.weighty = 1.0;

changesScrollPanel.add(new JButton(""
+ changesScrollPanel.getComponentCount()),
gridBagConstraints);
changesScrollPanel.validate();
} else {
System.out.println("ERROR"); //$NON-NLS-1$
}
}

/**
 * This method initializes changesScrollPane
 * 
 * @return javax.swing.JScrollPane
 */
private JScrollPane getChangesScrollPane() {
if (changesScrollPane == null) {
changesScrollPane = new JScrollPane();
changesScrollPane.setViewportView(getChangesScrollPanel());
}
return changesScrollPane;
}

/**
 * This method initializes changesScrollPanel
 * 
 * @return javax.swing.JPanel
 */
private JPanel getChangesScrollPanel() {
if (changesScrollPanel == null) {
changesScrollPanel = new JPanel();
changesScrollPanel.setLayout(new GridBagLayout());
changesScrollPanel.setBorder(BorderFactory.createEtchedBorder(EtchedBorder.LOWERED));
}
return changesScrollPanel;
}

/**
 * This method initializes jButton
 * 
 * @return javax.swing.JButton
 */
private JButton getJButton() {
if (jButton == null) {
jButton = new JButton();
jButton.setText("Add a button");
jButton.addActionListener(this);
}
return jButton;
}

/**
 * This method initializes jContentPane
 * 
 * @return javax.swing.JPanel
 */
private JPanel getJContentPane() {
if (jContentPane == null) {
final GridBagConstraints gridBagConstraints2 = new GridBagConstraints();
gridBagConstraints2.fill = GridBagConstraints.NONE;
gridBagConstraints2.gridx = 0;
gridBagConstraints2.gridy = 1;
gridBagConstraints2.weightx = 0.0;
gridBagConstraints2.anchor = GridBagConstraints.SOUTHEAST;
gridBagConstraints2.insets = new Insets(5,
0,
5,
5);
gridBagConstraints2.weighty = 0.0;
final GridBagConstraints gridBagConstraints = new GridBagConstraints();
gridBagConstraints.fill = GridBagConstraints.BOTH;
gridBagConstraints.gridx = 0;
gridBagConstraints.gridy = 0;
gridBagConstraints.weightx = 1.0;
gridBagConstraints.weighty = 1.0;
jContentPane = new JPanel();
jContentPane.setLayout(new GridBagLayout());
jContentPane.add(getChangesScrollPane(),
gridBagConstraints);
jContentPane.add(getJButton(),
gridBagConstraints2);
}
return jContentPane;
}

/**
 * This method initializes this
 * 
 * @return void
 */
private void initialize() {
this.setSize(517,
423);
setContentPane(getJContentPane());
setTitle("JFrame");
}

}

Thanks,
Chris

EDIT: Found what was wrong, needed to validate the changesScrollPane instead of the changesScrollPanel. Thanks for your help, I'm finally done
[ February 27, 2008: Message edited by: Chris Waguespack ]

[Brian Cole]

Originally posted by Chris Waguespack:
the scroll bars won't update until I resize the window. How do I fix this?

If the JPanel doesn't realize it needs to change size then its enclosing JScrollPane won't adjust its scroll bars.

It should work if you replace changesScrollPanel.validate() with changesScrollPane.validate(). Or actually, I would instead call changesScrollPane.revalidate() but the result is the same.

[edit: I see you figured this out as I was typing. cool.]
[ February 27, 2008: Message edited by: Brian Cole ]