Re: [jCrollPane]Positionning the view with a command

Knute Johnson <>
Sat, 18 Jul 2009 09:45:53 -0700
Daniel Moyne wrote:

I have a jCrollPane built with netbeans and I have many jPanels vertically
positionned in it and of course by using the vertical slider attached to the
jScrollPane I can position the view wherever I want.

Now I want by a java method depending of the index number of a particular
jPanel make this object visible within the window ; I know how many jPanels
I have got installed vertically and I can get a int variable in percentage
for this position regarding the vertical height :
int verticalPosition= (int) (index_of_my_Jpanel/number_of_Jpanels)
or maybe I can go with the index_of_my_Jpanel itself by setting for the
vertical slider a min index and a max index.

Now how do I recover information on the vertical slider to set its position
with my selected int variable ?

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class test extends JFrame {
     final NPanel[] panels = new NPanel[10];
     final JScrollPane sp;

     public test() {

         final JPanel p = new JPanel(new GridBagLayout());
         GridBagConstraints c = new GridBagConstraints();
         c.gridx = 0;

         for (int i=0; i<panels.length; i++) {
             panels[i] = new NPanel(i);

         sp = new JScrollPane(p);
         sp.getViewport().setPreferredSize(new Dimension(320,400));


         JTextField tf = new JTextField(10);
         tf.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent ae) {
                 JTextField tf = (JTextField)ae.getSource();
                 try {
                     int n = Integer.parseInt(tf.getText());
                     JViewport vp = sp.getViewport();
                 } catch (NumberFormatException nfe) {



     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 new test();

     class NPanel extends JPanel {
         final int n;

         public NPanel(int n) {
             this.n = n;
             setPreferredSize(new Dimension(320,240));

         public void paintComponent(Graphics g) {
             g.setFont(new Font("Arial",Font.BOLD,32));
             FontMetrics fm = g.getFontMetrics();
             String nStr = Integer.toString(n);
             int w = fm.stringWidth(nStr);
             int h = fm.getHeight();


Knute Johnson
email s/nospam/knute2009/

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