How to find visible row count in JTable?

[Premal Panchal]

Hi All,

I have one scroll pane in which i have set one table. Now my problem is to find visible row count in Scroll Pane area. I know that there is no direct function for that. But i tried to find Scroll Pane's height and all other relative functions, but by that way i got total height of Scroll Pane rather than visible area's height. Does anybody know how to find height of visible area of scroll pane? If I find that then I can get visible row count by dividing it to row height. Any help regarding this will apprieated.

Thanx and Regards,
Premal Panchal

[Joe Ess]

JViewPort is the class which represents the visible portion of a ScrollPane.

[Premal Panchal]

Hi,

I tried JViewPort also. But it gives me total hight of ViewPort rather than the visible part of JScrollPane. So is there any other way to do this? I tried all functions related to JViewPort of JScrollPane,JTable. But I couldn't get the proper result.

Thanx and Regards,

PremalPanchal

[Craig Wood]

Drag the bottom of the JFrame to activate the ComponentListener.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
public class ScrollPaneTest extends ComponentAdapter
{
    JTable table;
    JScrollPane scrollPane;
    JLabel label;
 
    public ScrollPaneTest()
    {
        table = getTable();
        scrollPane = new JScrollPane(table);
        scrollPane.addComponentListener(this);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(scrollPane);
        f.getContentPane().add(getLabel(), "South");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    public void componentResized(ComponentEvent e)
    {
        JViewport viewport = scrollPane.getViewport();
        Dimension extentSize = viewport.getExtentSize();     // JViewport
        Rectangle viewRect = viewport.getViewRect();         //         methods
        Rectangle visibleRect = viewport.getVisibleRect();   // JComponent method
        System.out.println("extentSize  = " + extentSize + "\n" +
                           "viewRect    = " + viewRect + "\n" +
                           "visibleRect = " + visibleRect + "\n");
        Point position = viewport.getViewPosition();         //  JViewport method
        int topRow = table.rowAtPoint(position);
        String item = (String)table.getValueAt(topRow, 0);
        int visibleRows = extentSize.height/table.getRowHeight();
        label.setText(String.valueOf(visibleRows) +
                      " rows visible starting with " + item);
    }
 
    private JTable getTable()
    {
        int cols = 4, rows = 32;
        String[] colNames = { "column 1", "column 2", "column 3", "column 4" };
        Object[][] data = new Object[rows][cols];
        for(int row = 0; row < 32; row++)
            for(int col = 0; col < 4; col++)
                data[row][col] = "item " + (row*cols + col + 1);
        return new JTable(data, colNames);
    }
 
    private JLabel getLabel()
    {
        label = new JLabel();
        label.setHorizontalAlignment(JLabel.CENTER);
        Dimension d = label.getPreferredSize();
        d.height = 25;
        label.setPreferredSize(d);
        return label;
    }
 
    public static void main(String[] args)
    {
        new ScrollPaneTest();
    }
}