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How to create a "Game Option/Pause Screen" in Swing?

Background: Making a game in Swing. It is simple turn base game. Not a whole lot going on. Because of this I didn't think I would need to implement a Game Tick. Rather, my thought was when a component got changed or needed to be updated just simply revalidate/repaint that component on the fly rather than repainting the whole screen.
I have a GameJPanel which currently has all the components on it. This JPanel is the one that contains the components that get revalidated/repainted etc.
I figured I could make JLayeredPane that holds GameJPanel and my OptionJPanel. Have a Button on GameJPanel that when pressed causes the OptionJPanel to show on top of it and having its JPanel 50% transparent (so it gives the affect it dims the GameJPanel).
However, once I did this what happened was that the GameJPanel started to replace OptionJPanel components (because of the events... etc; repainting of the components).
So currently I am at a loss on what to do. I'm thinking if I had some sort of game tick I wouldn't be having this issue, however, I am not 100% certain. I'm a little worried if I implemented a gametick that the events in game will cause the GameJPanel components to show through for half a second then get replaced. There are some events that cause components to repaint themselves without manually doing it (like quick example for JLabel setText();)
As an example of what I'm trying to go for.
I have tried with a CardLayout but I couldn't figure out how to have the OptionJPanel be on top of GameJPanel while seeing GameJPanel in the background (I tried setting background color, setOpaque(false)..., tried to limit Option JPanel size but I think the CardLayout stretches it (not 100% sure)) all I got was a gray background when doing so.
I would prefer not to go the CardLayout route because in the future I also plan on placing components on top of the GameJPanel (like someone clicks a button, have another panel on a different layer have a component slide in or out etc).
I use CardLayout a ton with my other components in GameJPanel to swap screens around, but haven't had the need to have the other components behind the one showing to show through.
Any ideas on how to go about this would be great or even example code that shows this.

As noted above, you would use a JDialog, a component that is easy to make (similar to making a JFrame) and easy to place. Simply place it "relative-to" the JFrame, e.g.,
myDialog.setLocationRelativeTo(myJFrame);
... and it will automatically center itself on the JFrame. The tricky part is dimming the underlying JFrame, and for this you would need to use a JGlassPane added to the JFrame's rootpane, one set with a background color that uses an alpha composite value. The tricky part with this is to draw the darker background without causing side effects, and to do this, please read Rob Camick's (StackOverflow user camickr) excellent tutorial on drawing in Swing with alpha composites which you can find here: Java Tips Weblog: Backgrounds with Transparency
An example of such a program is shown here:
import java.awt.Color;
import java.awt.Component;
import java.awt.Dialog.ModalityType;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;
public class DialogEg {
// path to example image used as "game" background
private static final String IMG_PATH = "https://upload.wikimedia.org/"
+ "wikipedia/commons/7/76/Jump_%27n_Bump.png";
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> createAndShowGui());
}
private static void createAndShowGui() {
// get the "game" background image, or exit if fail
BufferedImage img = null;
try {
URL imgUrl = new URL(IMG_PATH);
img = ImageIO.read(imgUrl);
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
// pass "game" image into main JPanel so that it will be drawn
DeMainPanel mainPanel = new DeMainPanel(img);
JFrame frame = new JFrame("Dialog Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.add(mainPanel); // add main JPanel to JFrame
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
}
// main JPanel
#SuppressWarnings("serial")
class DeMainPanel extends JPanel {
private BufferedImage img; // background image
// JButton action that shows the JDialog and darkens the glasspane
private PauseAction pauseAction = new PauseAction("Pause");
public DeMainPanel(BufferedImage img) {
super();
this.img = img;
add(new JButton(pauseAction));
}
// draw the "game" background image within the JPanel if not null
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (img != null) {
g.drawImage(img, 0, 0, this);
}
}
// size this JPanel to match the image's size
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet() || img == null) {
return super.getPreferredSize();
}
int width = img.getWidth();
int height = img.getHeight();
return new Dimension(width, height);
}
}
// Action / ActionListener for JButton -- shows JDialog and darkens glasspane
#SuppressWarnings("serial")
class PauseAction extends AbstractAction {
private static final int ALPHA = 175; // how much see-thru. 0 to 255
private static final Color GP_BG = new Color(0, 0, 0, ALPHA);
private DeDialogPanel deDialogPanel = new DeDialogPanel(); // jpanel shown in JDialog
public PauseAction(String name) {
super(name);
}
#Override
public void actionPerformed(ActionEvent e) {
// comp is our JButton
Component comp = (Component) e.getSource();
if (comp == null) {
return;
}
// create our glass pane
JPanel glassPane = new JPanel() {
#Override
protected void paintComponent(Graphics g) {
// magic to make it dark without side-effects
g.setColor(getBackground());
g.fillRect(0, 0, getWidth(), getHeight());
super.paintComponent(g);
}
};
// more magic below
glassPane.setOpaque(false);
glassPane.setBackground(GP_BG);
// get the rootpane container, here the JFrame, that holds the JButton
RootPaneContainer win = (RootPaneContainer) SwingUtilities.getWindowAncestor(comp);
win.setGlassPane(glassPane); // set the glass pane
glassPane.setVisible(true); // and show the glass pane
// create a *modal* JDialog
JDialog dialog = new JDialog((Window)win, "", ModalityType.APPLICATION_MODAL);
dialog.getContentPane().add(deDialogPanel); // add its JPanel to it
dialog.setUndecorated(true); // give it no borders (if desired)
dialog.pack(); // size it
dialog.setLocationRelativeTo((Window) win); // ** Center it over the JFrame **
dialog.setVisible(true); // display it, pausing the GUI below it
// at this point the dialog is no longer visible, so get rid of glass pane
glassPane.setVisible(false);
}
}
// JPanel shown in the modal JDialog above
#SuppressWarnings("serial")
class DeDialogPanel extends JPanel {
private static final Color BG = new Color(123, 63, 0);
public DeDialogPanel() {
JLabel pausedLabel = new JLabel("PAUSED");
pausedLabel.setForeground(Color.ORANGE);
JPanel pausedPanel = new JPanel();
pausedPanel.setOpaque(false);
pausedPanel.add(pausedLabel);
setBackground(BG);
int eb = 15;
setBorder(BorderFactory.createEmptyBorder(eb, eb, eb, eb));
setLayout(new GridLayout(0, 1, 10, 10));
add(pausedPanel);
add(new JButton(new FooAction("RESUME")));
add(new JButton(new FooAction("RESTART")));
add(new JButton(new FooAction("EXIT TO MAP")));
}
// simple action -- all it does is to make the dialog no longer visible
private class FooAction extends AbstractAction {
public FooAction(String name) {
super(name);
}
#Override
public void actionPerformed(ActionEvent e) {
Component comp = (Component) e.getSource();
Window win = SwingUtilities.getWindowAncestor(comp);
win.dispose(); // here -- dispose of the JDialog
}
}
}
The GUI looks like this initially:
but then when the dialog shows and the glass pane is darkened, it looks like this:

So after about a month of working on my game I was drawn to this post once again. I implemented part of my game with what DontKnowMuchButGettingBetter's way and also implemented this by just adding the components to the GlassPane so to speak (Made a JPanel, set it to be GlassPane, did whatever on that Panel)...
The later implementation (GlassPane), isn't the best way to go about this because then you can't use the glass pane for other useful things.
I came back to my original idea to use a JLayeredPane. Having different Components on different levels and working off that. My issue before was that when components were getting repainted, the components in the backer layers were over painting the ones in the front layer.
Well I just came across a method called isOptimizedDrawingEnabled()... By making this method always return false for the JLayeredPane I was able to achieve what I wanted.

Swing and Nimbus: Replace background of JPopupMenu (attached to JMenu)

Nimbus often looks great, but for certain color combinations the result is non-optimal. In my case, the background of a JPopupMenu does not fit, which is why I want to set it manually.
I'm on Java 7 and, interestingly, Nimbus fully ignores the setting of some properties in the UIManager (like PopupMenu.background). So my only option was to create a subclass of JPopupMenu that overrides paintComponent(...). I know, that's nasty, but at least it worked.
However, if you add a JMenu to another menu, it embeds it's own instance of JPopupMenu and I could not figure out how to replace it with my own subclass.
Even assigning an own PopupMenuUI to the embedded instance didn't bring any results. If inherited directly from JPopupMenu the overriden paint(...) method was called, but, not matter what I did, nothing was drawn. If inherited from javax.swing.plaf.synth.SynthPopupMenuUI paint isn't even called and the result is if I hadn't set an own PopupMenuUI at all.
So the simple question is: How do I adjust the background color of one JPopupMenu or (if that's easier) all of them on Java 7 using Nimbus as L&F?
Edit: Code example
Take a look at the following code and the result:
public static void main(final String[] args) {
try {
UIManager.setLookAndFeel(NimbusLookAndFeel.class.getCanonicalName());
UIManager.getLookAndFeelDefaults().put("PopupMenu.background", Color.GREEN);
UIManager.getLookAndFeelDefaults().put("Panel.background", Color.RED);
UIManager.getLookAndFeelDefaults().put("List.background", Color.BLUE);
} catch (ClassNotFoundException | InstantiationException
| IllegalAccessException | UnsupportedLookAndFeelException e) {
e.printStackTrace();
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200,200);
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));
JList list = new JList();
panel.add(list);
frame.getContentPane().add(panel);
JPopupMenu menu = new JPopupMenu();
menu.add(new JMenuItem("A"));
menu.add(new JMenuItem("B"));
menu.add(new JMenuItem("C"));
frame.setVisible(true);
menu.show(frame, 50, 50);
}
I know, some say that you should use UIManager.put(key, value) or UIManager.getLookAndFeelDefautls().put(key,value) before setting the L&F, but for me this does not bring any results (meaning: no changes to the default colors at all). The code above at least brings:
Same thing (meaning nothing) happens if you use JPopupMenu.setBackground(...). This is because Nimbus uses an internal painter, which computes the color from Nimbus' primary colors and ignores the components' property. In this example, you can use the following as workaround:
JPopupMenu menu = new JPopupMenu() {
#Override
public void paintComponent(final Graphics g) {
g.setColor(Color.GREEN);
g.fillRect(0,0,getWidth(), getHeight());
}
};
Which brings
However, this workaround does not work if you insert a JMenu which itself wraps a JPopupMenu you can't override:
JMenu jmenu = new JMenu("D");
jmenu.add(new JMenuItem("E"));
menu.add(jmenu);
gives, as expected:
You can retrieve this JPopupMenu using JMenu.getPopupMenu() but you can't set it. Even overriding this method in an own subclass of JMenu does not bring any results, as JMenu seems to access it's enwrapped instance of JPopupMenu without using the getter.

One way to do it is to color the background of the individual JMenuItems and make them opaque:
JMenuItem a = new JMenuItem("A");
a.setOpaque(true);
a.setBackground(Color.GREEN);
Then give the menu itself a green border to fill the rest:
menu.setBorder(BorderFactory.createLineBorder(Color.GREEN));
There may be an easy/more straightforward way out there, but this worked for me.

there are a few mistakes in both answers
and above mentioned way to required to override most UIDeafaults that have got impact to the another JComponents and its Color(s)
Nimbus has own Painter, one example for that ...
from code
import com.sun.java.swing.Painter;
import java.awt.*;
import javax.swing.*;
public class MyPopupWithNimbus {
public MyPopupWithNimbus() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(200, 200);
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
JList list = new JList();
panel.add(list);
frame.getContentPane().add(panel);
JPopupMenu menu = new JPopupMenu();
menu.add(new JMenuItem("A"));
menu.add(new JMenuItem("B"));
menu.add(new JMenuItem("C"));
JMenu jmenu = new JMenu("D");
jmenu.add(new JMenuItem("E"));
menu.add(jmenu);
frame.setVisible(true);
menu.show(frame, 50, 50);
}
public static void main(String[] args) {
try {
for (UIManager.LookAndFeelInfo laf : UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(laf.getName())) {
UIManager.setLookAndFeel(laf.getClassName());
UIManager.getLookAndFeelDefaults().put("PopupMenu[Enabled].backgroundPainter",
new FillPainter(new Color(127, 255, 191)));
}
}
} catch (Exception e) {
e.printStackTrace();
}
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
MyPopupWithNimbus aa = new MyPopupWithNimbus();
}
});
}
}
class FillPainter implements Painter<JComponent> {
private final Color color;
FillPainter(Color c) {
color = c;
}
#Override
public void paint(Graphics2D g, JComponent object, int width, int height) {
g.setColor(color);
g.fillRect(0, 0, width - 1, height - 1);
}
}

not the whole story - but looks like setting the opacity of menu/items to true partly solves it (as #Derek Richard already did for a item created under full application control):
UIDefaults ui = UIManager.getLookAndFeelDefaults();
ui.put("PopupMenu.background", GREEN);
ui.put("Menu.background", GREEN);
ui.put("Menu.opaque", true);
ui.put("MenuItem.background", GREEN);
ui.put("MenuItem.opaque", true);
and so on, for all types of items like radioButton/checkBox.
This still leaves a upper/lower grey area - don't know which part is responsible for that drawing. Removing the margin helps at the price of looking squeezed
// this looks not so good, but without the margins above/below are still grey
ui.put("PopupMenu.contentMargins", null);
There's a list of property keys in the tutorial.

Colorize a tab in a JTabbedPane using java swing

I am trying to change the background color of my tabs in a JTabbedPane. I tried JTabbedPane.setBackgroudAt(0, Color.GRAY) and JTabbedPane.setBackgroud(Color.GRAY) and the foreground too, but nothing happens. I changed the background of the panel inside the tab, still nothing.
Edit 1: I'm using UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); if this can help with the solution
Edit 2: Link to a example, https://www.dropbox.com/s/0krn9vikvkq46mz/JavaApplication4.rar

You can change the background color of the tab using setBackgroundAt(), as shown here.
You can change the background color of the tab's content using setBackground(), as shown here. Typically you have to do this on the tab's content, as the enclosing JTabbedPane background color is obscured by the content.
If you still have trouble, please edit your question to include an sscce based on either example that exhibits the problem you envounter.
Addendum: Combining the methods is also possible:
import java.awt.*;
import java.awt.event.*;
import java.util.Random;
import javax.swing.*;
public class JTabbedTest {
private static JTabbedPane jtp;
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jtp = new JTabbedPane();
jtp.setPreferredSize(new Dimension(320, 200));
jtp.addTab("Reds", new ColorPanel(0, Color.RED));
jtp.setBackgroundAt(0, Color.RED);
jtp.addTab("Greens", new ColorPanel(1, Color.GREEN));
jtp.setBackgroundAt(1, Color.GREEN);
jtp.addTab("Blues", new ColorPanel(2, Color.BLUE));
jtp.setBackgroundAt(2, Color.BLUE);
f.add(jtp, BorderLayout.CENTER);
f.pack();
f.setVisible(true);
}
});
}
private static class ColorPanel extends JPanel implements ActionListener {
private final Random rnd = new Random();
private final Timer timer = new Timer(1000, this);
private Color color;
private Color original;
private int mask;
private JLabel label = new JLabel("Stackoverflow!");
private int index;
public ColorPanel(int index, Color color) {
super(true);
this.color = color;
this.original = color;
this.mask = color.getRGB();
this.index = index;
this.setBackground(color);
label.setForeground(color);
this.add(label);
timer.start();
}
#Override
public void actionPerformed(ActionEvent e) {
color = new Color(rnd.nextInt() & mask);
this.setBackground(color);
jtp.setBackgroundAt(index, original);
}
}
}

most of method for JTabbedPane is protected in the API, and not accesible from Swing methods
have to look for Custom XxxTabbedPaneUI, override these methods, and could be accesible from outside
correct way would be to implement Custom Look & Feel only, part of them override JTabbedPane
example for Custom XxxTabbedPaneUI

You should consider using a Look and Feel that does what you want, or failing that, changing the default UIManger settings for a JTabbedPane:
UIManager.put("TabbedPane.background", Color.GRAY);
If you opt for the latter, it must be done before you create your GUI.
For more on this, please see Rob Camick's excellent blog on the subject: UIManager Defaults.
Edit: I was wrong. It should be:
UIManager.put("TabbedPane.unselectedBackground", Color.GRAY);
But note that this may not work with every Look and Feel.

It may be a problem that there is nothing added yet to the tab.
Try setting the content manager of the content panel to BorderLayout, adding a JPanel with BorderLayout. Center and then coloring that panel.

How to effectively add a call back method for the JPanel.add(component) method?

edit: now solved, but can't mark as accepted for two days
In my class I have a JScrollPanel and that has a JPanel inside of it too.
My code resembles something like this:
import java.awt.Color;
import java.awt.Container;
import javax.swing.*;
public class MyClass {
private JPanel p;
private JScrollPane s;
private Container contentPane;
public MyClass(Container contentPane) {
this.contentPane = contentPane;
this.p = new JPanel();
this.p.setBackground(Color.WHITE);
BoxLayout boxLayout = new BoxLayout(this.p, BoxLayout.Y_AXIS);
this.p.setLayout(boxLayout);
this.s = new JScrollPane(this.p);
this.s.setSize(400, 364);
this.contentPane.add(this.s);
}
public final JLabel makeJLabel(String message) {
JLabel jLabel = new JLabel("<html><p style=\"padding-left:15px;padding-right:15px;width:280px;\">" + message.replaceAll("(\r\n|\n)", "<br />") + "</p></html>");
/*
some stuff here to calculate pref/max size and add an imageicon
*/
p.add(jLabel);
this.p.revalidate();
this.s.revalidate(); //just added because the above line made no effect
scrollToBottom();
return jLabel;
}
public void scrollToBottom() {
JScrollBar vertical = s.getVerticalScrollBar();
vertical.setValue(vertical.getMaximum());
}
}
Elsewhere in my class I have a method which adds a JLabel to the JPanel. This actual method is quite long, so I wont post it all, but this is the code which adds it to the panel: p.add(jLabel1);
All of these JLabels are added in a vertical fashion thanks to the Box Layout.
After the JLabel has been added to the JPanel I want the JScrollPane to scroll to the bottom. But this can't be done until after the JPanel has actually been drawn (painted?) onto JPanel. Otherwise I get this result:
So what I want to do is add some form of listener to the JPanel which detects when my JLabel has been painted to it, so that I can tell my JScrollPane to scroll to the bottom. I have already written a method which scrolls the pane to the bottom, but I don't have anywhere suitable to call it from yet.
Does anyone have any ideas on this please? Thanks.

I'm assuming you just want the label to be visible in the scrollpane so I would gues you should be able to do something like:
panel.add( label );
panel.revalidate();
label.scrollRectToVisible( label.getBounds() );
Or if you really do want to just scroll bo the bottom then you would do something like:
panel.revalidate();
scrollPane.getVerticalScrollBar().setValue( getVerticalScrollBar().getMaximum() );
Both of these answers assume the GUI is already visible.

The first part of Rob's answer is the way to go - the missing piece is to wrap the scrollRectToVisible into SwingUtilities.invokeLater. Doing so delays the scrolling until all pending events are processed, that is until all internal state is updated. A code snippet (in swingx test support speak, simply replace the frame creation and scrollpane wrapping with manually created code)
final JComponent panel = new JPanel();
panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));
for(int i = 0; i < 10; i++)
panel.add(new JLabel("initial message " + i));
JXFrame frame = wrapWithScrollingInFrame(panel, "scroll to bottom");
Action action = new AbstractAction("addMessage") {
int count;
#Override
public void actionPerformed(ActionEvent e) {
final JLabel label = new JLabel("added message " + count++);
panel.add(label);
panel.revalidate();
SwingUtilities.invokeLater(new Runnable() {
public void run() {
label.scrollRectToVisible(label.getBounds());
}
});
}
};
frame.add(new JButton(action), BorderLayout.SOUTH);
show(frame);

Scratched my head for ages over this, but after asking the question I finally figured it out.
To solve my problem all I need to do was listen for a change in value in the JScrollPane's scroll bar. If it changed, done some calculations, and scroll to the bottom if necessary.
Care has to be taken to ensure that you're not overriding the user moving the scroll bar however.
In particular you're looking at the track which is an AdjustmentEvent. This event is also fired when a user moves the scroll bar.
In order to allow the user to scroll without forcibly scroll it to the bottom, I always keep track of the maximum scroll bar value. If when track is fired the new max value is higher than the current one then a new item has been added and we should think about scrolling to the bottom. If the values are equal then the user is scrolling the scroll bar and we do nothing.
The event listeners can be found on this website and can be make to work very easily: Listening for Scrollbar Value Changes in a JScrollPane Container
import java.awt.Color;
import java.awt.Container;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import javax.swing.*;
public class MyClass {
private JPanel p;
private JScrollPane s;
private Container contentPane;
private int scrollBarMax;
public MyClass(Container contentPane) {
this.contentPane = contentPane;
this.p = new JPanel();
this.p.setBackground(Color.WHITE);
BoxLayout boxLayout = new BoxLayout(this.p, BoxLayout.Y_AXIS);
this.p.setLayout(boxLayout);
this.s = new JScrollPane(this.p);
this.s.setSize(400, 364);
this.contentPane.add(this.s);
this.s.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener(){
#Override
public void adjustmentValueChanged(AdjustmentEvent evt) {
if (evt.getValueIsAdjusting()) {
return;
}
if (evt.getAdjustmentType() == AdjustmentEvent.TRACK) {
if (scrollBarMax < s.getVerticalScrollBar().getMaximum()) {
if ((s.getVerticalScrollBar().getValue() + s.getVerticalScrollBar().getSize().height) == scrollBarMax) {
//scroll bar is at the bottom, show the last added JLabel
scrollBarMax = s.getVerticalScrollBar().getMaximum();
scrollToBottom();
} else {
//scroll bar is not at the bottom, user has moved it
scrollBarMax = s.getVerticalScrollBar().getMaximum();
}
}
}
}
});
scrollBarMax = s.getVerticalScrollBar().getMaximum();
}
public final JLabel makeJLabel(String message) {
JLabel jLabel = new JLabel("<html><p style=\"padding-left:15px;padding-right:15px;width:280px;\">" + message.replaceAll("(\r\n|\n)", "<br />") + "</p></html>");
/*
some stuff here to calculate pref/max size and add an imageicon
*/
p.add(jLabel);
scrollBarMax = s.getVerticalScrollBar().getMaximum();
return jLabel;
}
public void scrollToBottom() {
JScrollBar vertical = s.getVerticalScrollBar();
vertical.setValue(vertical.getMaximum());
}
}

Slide JPanel Content in a JForm on Java

I have a question. I want to make a swing form that, when clicking in a button he slides a panel (with his content) to the left so the panel on the right replaces it with a smooth effect.
I Have tried to do a while how checks the size of the panel and then minimize it and shows the next one like this :
while (jpanelprincipal1.getWidth() < 439 || jpanelprincipal1.getHeight() > 250)
{
int panel1width = jpanelprincipal1.getWidth();
int panel2height = jpanelprincipal1.getHeight();
jpanelprincipal1.setSize(panel1width -- , panel2height --);
jpanelprincipal2.setSize(440,250);
}
I used this trick in C# but with the Application.DoEvent(); (how obviously it's not available on java).
Is there anyway i can make a slide effect of 2 or more panels?
BTW : Sorry for my very bad english !
Thanks In Advance,
Luis Da Costa

he slides a panel (with his content) to the left so the panel on the right replaces it with a smooth effect
You question mentions you want the panel to "slide", but the code looks like you are trying to get the panel to "shrink", so it is replaced by another panel.
Assuming you have two panels each with the same size, then you can "slide" one out of view while the other slides into view.
To do this you an use a panel with a GridLayout. This way each component will be the same size. Then you add the panel to a scrollpane without any scrollbars. The size of the scrollpane will need to be set to the size of the first compnoent. Then you can "slide" the two panels by changing the position of the viewport. So in your Timer you would have code something like:
JViewport viewport = scrollPane.getViewport();
Point position = viewport.getViewPosition();
position.x += 5;
viewport.setViewPosition( position );
You would then stop the Timer when the position is greater than the size of the component.

As suggested by #HFOE, javax.swing.Timer is a good choice for animation. The setDividerLocation() method of JSplitPane can be called from the ActionListener. See How to Use Split Panes for additional options.
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
/** #see http://stackoverflow.com/questions/5069152 */
public class SplitPaneTest {
double ratio = 0.5;
double delta = ratio / 10;
private void create() {
JFrame f = new JFrame("JSplitPane");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
MyPanel p1 = new MyPanel(Color.red);
MyPanel p2 = new MyPanel(Color.blue);
final JSplitPane jsp = new JSplitPane(
JSplitPane.HORIZONTAL_SPLIT, true, p1, p2);
Timer timer = new Timer(200, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
ratio += delta;
if (ratio >= 1.0) {
ratio = 1.0;
delta = -delta;
} else if (ratio <= 0) {
delta = -delta;
ratio = 0;
}
jsp.setDividerLocation(ratio);
}
});
f.add(jsp);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
timer.start();
}
private static class MyPanel extends JPanel {
Color color;
public MyPanel(Color color) {
this.color = color;
this.setPreferredSize(new Dimension(300, 300));
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(color);
g.drawLine(0, 0, getWidth(), getHeight());
g.drawLine(getWidth(), 0, 0, getHeight());
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new SplitPaneTest().create();
}
});
}
}

I would probably do this with a Swing Timer. Change a class field representing the x, y position of the sliding JPanel in the timer's ActionListener and then call repaint on the container holding the JPanels. A JLayeredPane could work well as the container for the sliding JPanels.
Edit 1: regarding your request for code, I think the best thing is for you to try to create a very small compilable runnable program that attempts to do this, and then post your code with an explanation of your program's behavior as an edit to your original post. Also send us a comment to notify us of your changes. Then we can inspect your code, test it, modify it, and help you mold it into a working program. This is called creating a "Short, Self Contained, Correct (Compilable), Example" or SSCCE (please check the link).