all individual panels are not shown inside root panel

Question

I want to add multiple jpanels to jpanel.So i added a root panel to jscrollpane.and then added all individual jpanels to this root panel.I made jscrollpane's scrolling policy as needed.i.e HORIZONTAL_SCROLLBAR_AS_NEEDED,VERTICAL_SCROLLBAR_AS_NEEDED. But the problem is all individual panels are not shown inside root panel.

Code:

JScrollPane scPanel=new JScrollPane();

JPanel rootPanel=new JPanel();
rootPanel.setLayout(new FlowLayout());

JPanel indPanel = new JPanel();
rootPanel.add(indPanel);

JPanel indPanel2 = new JPanel();
rootPanel.add(indPanel2);

//.....like this added indPanals to rootPanel.
scPanel.setViewPortView(rootPanel);
//scPanel.setHorizontalScrollPolicy(HORIZONTAL_SCROLLBAR_AS_NEEDED);

And one more thing is, as i scroll the scrollbar the panels are going out of jscrollpane area. I am not able to see all individual panels, Please suggest me.

Edit: code snippet from double post:

MosaicFilesStatusBean mosaicFilesStatusBean = new MosaicFilesStatusBean();
DefaultTableModel tableModel = null;
tableModel = mosaicFilesStatusBean.getFilesStatusBetweenDates(startDate, endDate);
if (tableModel != null) {
    rootPanel.removeAll();        
    rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS));      
    for (int tempRow = 0; tempRow < tableModel.getRowCount(); tempRow++) {

        int fileIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 0).toString());
        String dateFromTemp = tableModel.getValueAt(tempRow, 3).toString();
        String dateToTemp = tableModel.getValueAt(tempRow, 4).toString();
        int processIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 5).toString());
        int statusIdTemp = Integer.parseInt(tableModel.getValueAt(tempRow, 6).toString());
        String operatingDateTemp = tableModel.getValueAt(tempRow, 7).toString();                
        MosaicPanel tempPanel =           
           new MosaicPanel(fileIdTemp, dateFromTemp, dateToTemp, processIdTemp, statusIdTemp, operatingDateTemp);             
        rootPanel.add(tempPanel);             
    }
    rootPanel.revalidate();
}

Answer 1

The main reason, why you couldn't see your JPanel is that you are using FlowLayout as the LayoutManager for the rootPanel. And since your JPanel added to this rootPanel has nothing inside it, hence it will take it's size as 0, 0, for width and height respectively. Though using GridLayout such situation shouldn't come. Have a look at this code example attached :

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

public class PanelAddition
{
    private void createAndDisplayGUI()
    {
        JFrame frame = new JFrame("Panel Addition Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel contentPane = new JPanel();
        contentPane.setLayout(new GridLayout(0, 1));        
        JScrollPane scroller = new JScrollPane();

        CustomPanel panel = new CustomPanel(1);
        contentPane.add(panel);
        scroller.setViewportView(contentPane);
        frame.getContentPane().add(scroller, BorderLayout.CENTER);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        for (int i = 2; i < 20; i++)
        {
            CustomPanel pane = new CustomPanel(i);
            contentPane.add(pane);
            contentPane.revalidate();
            contentPane.repaint();
        }
    }

    public static void main(String... args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            public void run()
            {
                new PanelAddition().createAndDisplayGUI();
            }
        });
    }
}

class CustomPanel extends JPanel
{

    public CustomPanel(int num)
    {
        JLabel label = new JLabel("" + num);
        add(label);
    }

    @Override
    public Dimension getPreferredSize()
    {
        return (new Dimension(200, 50));
    }
}

Answer 2

Don't use FlowLayout for the rootPanel. Instead consider using BoxLayout:

JPanel rootPanel=new JPanel();
// if you want to stack JPanels vertically:
rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS)); 

Edit 1
Here's an SSCCE that's loosely based on your latest code posted:

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.util.Random;

import javax.swing.*;

@SuppressWarnings("serial")
public class PanelsEg extends JPanel {
   private static final int MAX_ROW_COUNT = 100;
   private Random random = new Random();
   private JPanel rootPanel = new JPanel();

   public PanelsEg() {
      rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS));
      JScrollPane scrollPane = new JScrollPane(rootPanel);
      scrollPane.setPreferredSize(new Dimension(400, 400)); // sorry kleopatra

      add(scrollPane);

      add(new JButton(new AbstractAction("Foo") {

         @Override
         public void actionPerformed(ActionEvent arg0) {
            foo();
         }
      }));
   }

   public void foo() {
          rootPanel.removeAll();        
          // rootPanel.setLayout(new BoxLayout(rootPanel, BoxLayout.PAGE_AXIS)); // only need to set layout once 
          int rowCount = random.nextInt(MAX_ROW_COUNT);
         for (int tempRow = 0; tempRow < rowCount ; tempRow++) {

              int fileIdTemp = tempRow;
              String data = "Data " + (tempRow + 1);
              MosaicPanel tempPanel =           
                 new MosaicPanel(fileIdTemp, data);             
              rootPanel.add(tempPanel);             
          }
          rootPanel.revalidate();
          rootPanel.repaint(); // don't forget to repaint if removing
   }

   private class MosaicPanel extends JPanel {

      public MosaicPanel(int fileIdTemp, String data) {
         add(new JLabel(data));
      }

   }

   private static void createAndShowGui() {
      PanelsEg mainPanel = new PanelsEg();

      JFrame frame = new JFrame("PanelsEg");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

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

This SSCCE works, in that it easily shows removing and adding JPanels to another JPanel that is held by a JScrollPane. If you're still having a problem, you should modify this SSCCE so that it shows your problem.