Problem with JPanel in a JScrollPane

Hi all,
I am devloping an application where in i insert the JPanel's object in the JScrollPane object. Intitially the size of the JPanel's object is more than the size of the JScrollPane object.At this point fo time i can drag the nob of the scrollpane to the extent of the size of the JPanel's object. Now When i move the mouse behond the size of the JPanel i am increasing the size of the JPanel's object but i cant move the nob of the scrollpane object behond the original limit.
For example : when you open a notepad there will be scrollbar without the nob if you keep on pressing the enter key the size of the text area increases and we can see the scroll bar now. I what the similar functionality but
instead of TextArea i need the panel.
If any of you have solved this problem or know the solution please do inform. I need to solve this problem very urgently. Please do help me out.
Thanks in Advance.
regards
Ravi

Hi all,
I got the solution.we need to revalidate the panel object.
i.e JPanel.revalidate()
regards
Ravi Kumar

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First , I add a Jscrollpane to the panel and I don't
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Example code??
Can't tell what's wrong otherwise.
First , I add a Jscrollpane to the panel and I don't
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Hello,
i have a problem with updateUI(), here's a simple
example what's wrong. just compile and run the
following piece of code and look what happens after 2
seconds: the left panel will be decrease its width
after calling updateUI(), but why? is it a bug of
updateUI() or is it my fault?updateUI() its called when the L&F is changed, there is
rarely a case when you need to call updateUI().
Why do you call updateUI() if you remove the call to updateUI()
everything will work OK.
merry xmas

Problem with a JList and JScrollpane

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hai ashrivastava..
thank u for sending this one..now i got some more problems with that screen .. actually i am added one JPanel to JFrame with BorderLayout at south..the problem is when i am drawing diagram..the part of diagram bellow JPanel is now not visible...and one more problem is ,after adding 6 ro 7 buttons remaing buttons are not vissible..how to increase the size of that JPanel...to add that JPanel i used bellow code
JFrame f = new JFrame();
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Hi
JFrame f = new JFrame();
JPanel panel = new JPanel();
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import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.util.List;
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import javax.swing.event.*;
import javax.swing.border.*;
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                    secondPanel.setStart(start);
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        gbc.weighty = 0;
        gbc.weightx = 1.0;
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                JSlider source = (JSlider)ce.getSource();
                if(secondPanel != null) {
                    secondPanel.setZoomFactor((double)source.getValue());
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            secondPanel = new BackPanel3("images/cougar.jpg", 850, 1100);
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        return secondPanel;
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        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new PP3();
class BackPanel3 extends JPanel implements MouseListener,
                                           MouseMotionListener{
    String imgPath = null;
    BufferedImage image;
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    List<JLabel> labels;     // declaration for j2se 1.5+
//    List labels;           // j2se 1.4-
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        addMouseMotionListener(this);
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        labels = new ArrayList<JLabel>();    // j2se 1.5+
//        labels = new ArrayList();          // j2se 1.4-
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        showLocations = !showLocations;
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        Point p = e.getPoint();
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            JLabel label = (JLabel)labels.get(j);
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        dragging = false;
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        try{
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Hi,
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Thanks for your response. I will try that when I get home, although I will be surprised if that works because I am already using setPreferredSize() . It seemed to me that once a Jframe's content pane gets assigned to a JDesktopPane, then the JPanel no longer has anywhere to draw itself, as according to the Sun documentation, you can only add a JInternalFrame to a JDesktopPane.
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Thanks,
Paul

Weird problem with jpanel vs jframe

I'm using jmathplot.jar from JMathTools which lets me do 3d plotting. I used a JFrame to get some code to work and it worked fine. Here's the code that worked for a JFrame:
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        myYRange = new double[10];
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                double x = i/10;
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                myXRange[(int) i] = x;
                myYRange[(int) j] = y;
                myZValues[(int) i][(int) j]= Math.cos(x*Math.PI)*Math.sin(y*Math.PI);
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setSize(600, 600);
setContentPane(myPanel);
setVisible(true);to
this.add(myPanel);and added these two lines to createGUI():
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        setContentPane(view);When I run it however, it appears really really small. It seems like its drawing the panel to the default size of the applet viewer and doesn't resize it when I resize the applet. I don't know if it's a problem with the library or if I'm doing something wrong in my applet.

However, as you can see, my main class is a JApplet because ideally I want View to be a JPanel that I add to the applet. All I did was change "extends JFrame" to "extends JApplet" and (...)What do you mean? View extends JApplet? I thought View was meant to extend JPanel in the end...
When I run it however, it appears really really small. It seems like its drawing the panel to the default size of the applet viewer and doesn't resize it when I resize the applet.Or, the panel has its preferred size, and this latter is too small. Actually the panel has the size its container's layout manager awards it (taking or not the panel's preferred, minimum, and maximum sizes into account). See the tutorial on [layout managers|http://java.sun.com/docs/books/tutorial/uiswing/layout/index.html] .
In particular, this line adds the myPanel to a parent panel (presumably, it is in class View which extends JPanel, whose default layout is FlowLayout):
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N.B.: there are a lot of "likely" and "presumably" in my reply: in order to avoid hardly-educated guesses especially on what is or isn't in your actual code, you'd better provide an SSCCE , which means reproducing the problem without the 3rd party library.

Problem with JPanel and JScrollPane

Hey,
I have a class which extends JPanel. Inside this class I would like to have a JScrollPane.
However, it does not seem to work.
public class Summary extends JPanel
     JScrollPane scrollPane;
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          p = new JPanel()
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                             /// do painting here!!!!
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          p.setPreferredSize(new Dimension(240,500));
          p.add(new JButton("test"));
          scrollPane = new JScrollPane(p);
          scrollPane.setLayout(null);
          scrollPane.setBounds(0,0,240,290);
          scrollPane.setBorder(BorderFactory.createLineBorder(Color.GREEN));
          add(scrollPane);
     }Any advice????
thanks in advance

Any advice????ditch this
setLayout(null);

Problem with JPanel on Mac

Hi,
I have a Jpanel with BorderLayout which has two components. First one is a JScrollpane which sits at CENTER and another is JEditorPane which sits at south. JScrollPane itself is over a JEditorPane ..... PROBLEM is I can't see the component sitting at SOUTH, any focus???

Hi,
I haven't seen this before. Is it possible to get some sample code that illustrates the problem? Feel free to email me at [email protected] (please remove any attachment extension) and I'll take a look.
Moving discussion to the Problems & Bugs forum.
Thanks,
Chris

Problem with JPanel and/or Thread

Hello all,
I have the following problem.
I have a JFrame containing to JPanels. The JPanels are placed
via BorderLayout.
JPanel #1 is for moving a little rectangle (setDoubleBufferd), it is
a self defined object extending JPanel.
The paint methon in JPanel #1 has been overwritten to do the drawings.
JPanel #2 contains 4 JButtons, but they have no effect at the
moment. It is an "original" JPanel.
The class extending JFrame implemented the interface Runnable and
is started in its own thread.
After starting the programm everthing looks fine.
But if I press a Button in the second JPanel this button is painted in
the top left corner of my frame. It changes if I press another button.
Any help would be appreciated.
Thanks.
Ralf

I have a JFrame containing to JPanels. The JPanels are
placed
via BorderLayout.The type of Layout does not seem to be relevant
>
JPanel #1 is for moving a little rectangle
(setDoubleBufferd), it is
a self defined object extending JPanel.
The paint methon in JPanel #1 has been overwritten to
do the drawings.
JPanel #2 contains 4 JButtons, but they have no effect
at the
moment. It is an "original" JPanel.
The class extending JFrame implemented the interface
Runnable and
is started in its own thread.
After starting the programm everthing looks fine.
But if I press a Button in the second JPanel this
button is painted in
the top left corner of my frame. It changes if I press
another button.
I noticed you solved this by painting the whole JFrame.
Yeh Form time to time I get this problem too......
Especially if the screen has gone blank - by going and having a cup of tea etc -
Text from one Panel would be drawn in another.. annoying
At first it was because I changed the state of some Swing Components
not from the Event Thread.
So make sure that your new Thread doesn't just blithely call repaint() or such like cos that leads to problems
but rather something like
SwingUtilities.invokeLater( new Runnable()
public void run()
MyComponent.repaint();
});However I still get this problem using JScrollPanes, and was able to fix it by using the slower backing store method for the JScrollPane
I could not see from my code how something on one JPanel can get drawn on another JPanel but it was happening.
Anyone who could totally enlighten me on this?

Problem with JPanel, JMenuBar

Hi, I'm new here so I'm not even sure if I'm posting in the correct forum ^^
I usually don't have problems when building a JFrame and adding items into it but now I'm confused.
When the JFrame is "built", I get a NullPointerException from the Panel's paintComponent method when it's trying to draw an image (g.drawImage())
This is the whole JPanel class
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class PanneauDe extends JPanel
private static final String [] TAB_IMAGE = { "De1.GIF", "De2.GIF", "De3.GIF",
                                               "De4.GIF", "De5.GIF", "De6.GIF" };
private static final int [] TAB_FREQUENCE = {0,0,0,0,0,0};
private static final int SIDE = 100;
private De unDe;
private ImageIcon imageDe;
private boolean aFirstTime;
private int aX, aY;
public PanneauDe()
    unDe = new De();
    aX = aY = 0;
    aFirstTime = true;
    addMouseListener(new EcouteurSouris());
public String getStats()
    String statsMsg = "";
    for ( int iPos = 0; iPos < TAB_FREQUENCE.length; iPos ++ )
      statsMsg += "Face " + (iPos + 1) + " : " + TAB_FREQUENCE[iPos] + " fois\n\n";
    return statsMsg;
public String getTotal()
    int total = 0;
    for ( int iPos = 0; iPos < TAB_FREQUENCE.length; iPos ++ )
      total += TAB_FREQUENCE[iPos];
    return "Le d� a �t� lanc� " + total + " fois";
public void throwDice()
    unDe.throwAgain();
    TAB_FREQUENCE[unDe.getFace() - 1] ++;
public void paintComponent (Graphics g)
    super.paintComponent(g);
    g.drawImage (imageDe.getImage(), aX, aY, null); // <---- THIS GENERATES THE NULLPOINTEREXCEPTION
class EcouteurSouris extends MouseAdapter
    public void mouseClicked (MouseEvent pMouseEvent)
      aX = pMouseEvent.getX();
      aY = pMouseEvent.getY();
      throwDice();
      imageDe = new ImageIcon(TAB_IMAGE[unDe.getFace() - 1]);
      repaint();
}When I click in the windows, a picture of a dice (different side, randomly generated by the method throwDice() ), when I click again the first image dissapear and another one appears... and I make statistics about the results.
I tried ...
public void paintComponent (Graphics g)
    super.paintComponent(g);
    //g.drawImage (imageDe.getImage(), aX, aY, null);
class EcouteurSouris extends MouseAdapter
    public void mouseClicked (MouseEvent pMouseEvent)
      aX = pMouseEvent.getX();
      aY = pMouseEvent.getY();
      throwDice();
      imageDe = new ImageIcon(TAB_IMAGE[unDe.getFace() - 1]);
      Graphics g = getGraphics();
      g.drawImage (imageDe.getImage(), aX, aY, null);
      g.dispose();
    }Everything works correctly, no more NullPointerException, but the images don't dissapear when I click again. They just stay there.
I'm not completly familiar with the repaint/dispose/paintComponent but I really don't understand why i get this NullPointerException error :\
If you see some weird words in the code, it's because i'm canadian-frenchy! :)
Full program is here

The real question is why are you trying to override the paintComponent() method. Just add the image to a JLabel and add the label to a panel.
However, the problem is that the paintComponent() method is invoked when the frame is shown and since you don't create the image until you do a mouseClick, the image in null.

Problem with JPanel

hello everyone!
i want to create a GUI consisting of a JTextField and a Jbutton which should be North aligned
and a JTextArea with a scrollbar south aligned. i created the following code but the button appears cut.
what's going wrong? could you help me?
Thanks!
Here is the code :
      panel=new JPanel();
      panel2=new JPanel();
      enterField = new JTextField(20);
      button=new JButton("Send");
      enterField.setEnabled( false );
      panel.setLayout(new FlowLayout(FlowLayout.LEFT));
      panel.add(enterField);
      panel.add(button);
      displayArea = new JTextArea(10,15);
      displayArea.setEnabled( false );
      scroller = new JScrollPane( displayArea );
      panel2.add(displayArea);
      panel2.add(scroller);
      Container container = getContentPane();
      container.add( panel, BorderLayout.NORTH );
      container.add( panel2, BorderLayout.SOUTH );
      setSize( 300, 150 );
      setVisible( true );

i changed the code as following but now the label, textfield and the button
all appear in the same line. But i want they appear the one under the other.
why does this happen?
      panel=new JPanel();
      panel2=new JPanel();
      label=new JLabel("Choose a number from 1 to 10:");
      enterField = new JTextField(8);
      button=new JButton("Send");
      enterField.setEnabled( false );
      panel.setLayout(new FlowLayout(FlowLayout.CENTER));
      panel.add(label);
      panel.add(enterField);
      panel.add(button);
displayArea = new JTextArea(5,18);
      displayArea.setEnabled( false );
      scroller = new JScrollPane( displayArea );
      panel2.add(scroller);
      Container container = getContentPane();
      container.add( panel, BorderLayout.NORTH );
      container.add( panel2, BorderLayout.SOUTH );
      //setSize(400,250);
      pack( );
      setVisible( true );

Problem with JPanel after rotation

Hi,
I am developing a graphics editor like mspaint. I have JPanel as my drawing canvas. now the problem is when I rotate the canvas, co-ordinates on the canvas are also getting rotate with it. for example if top-left corner is (0,0) initially then after rotating it 90 degree top-right corner becomes (0,0) and same for all the points on the canvas.
the code i m using for rotation is
contentPanel = new JPanel(){
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
Rectangle rect=g2.getClipBounds();
if(rotation!=0){
double angle = rotation * Math.PI/2;
g2.rotate(angle,getWidth()/2,getHeight()/2);
rect=g2.getClipBounds();
setPreferredSize(new Dimension(rect.width,rect.height));
super.paintComponent(g);
revalidate();
};

Whats your question?
If you rotate it, of course the points will rotate, they have to.

Problem with JPanel in a JScrollPane

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