Problem with JTable

[Akhil Jain]

Hi guys,

I am facing some problem here from last two days, and not getting a way to solve it properly.

Problem Description:
I have a file which contains thousands of records, i want to show all those records in JTable, caching them all is a bad thing, since i could run in to OutOfMemory issue. so i thought of using pagination (did it successfully though) but the pagination with next and previous button is not a very user-friendly approach, so i thought of changing the vertical scroll bar behaviour to reflect pagination internally.
Meaning:
User will be given an illusion that Table contains all thousands of records but in reality only those records will be kept in memory which is visible to user. On slidding the Vertical scroll Bar knob up and down will eventually controll the fetching of records from file.

I have created a sample program for it, but i am not able to get it working properly, Any help on this , would be highly appreciated.

Files i have written is as follows:
1. OneLinerFileWriter.java (for testing purpose)
2. OneLinerFileReader.java (for testing purpose)
3. CustomTableModel.java
4. TableFrame.java

Here are the codes for the same:

package com.akhil;
 
import java.io.File;
import java.io.FileWriter;
 
public class OneLinerFileWriter {

public static void main(String[] args) throws Exception {
FileWriter fw = new FileWriter(new File("log.txt"));
for(int i=1;i<=50;i++) {
fw.write("Hello"+i);
fw.write('\n');
}
fw.close();
}
}
    

 package com.akhil;
 
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;
import java.util.ArrayList;
import java.util.List;
 
public class OneLinerFileReader {
 
public static void main(String[] args) throws Exception {
 
OneLinerFileReader reader = new OneLinerFileReader();
reader.getLineAtIndex(5500);
reader.getLineInRange(9000, 9010);
}
 
public void getLineAtIndex(int index) throws FileNotFoundException, IOException {
String line;
LineNumberReader in = new LineNumberReader(new FileReader(new File("log.txt"))); 
while((line = in.readLine()) !=null) {
if(in.getLineNumber()==index) {
System.out.println("line at index "+index+" is: "+line);
}
}
in.close();
}

public List getLineInRange(int fromIndex, int toIndex){
List<String> list = null;
try {
list = new ArrayList<String>();
String line= null;
LineNumberReader in = new LineNumberReader(new FileReader(new File("log.txt"))); 
while((line = in.readLine()) !=null) {
if(in.getLineNumber() >= fromIndex && in.getLineNumber() <= toIndex) {
list.add(line);
}
}

//Iterator<String> itr =list.iterator();
//while(itr.hasNext()) {
//System.out.println(itr.next());
//}
in.close();
}catch(Exception e) {
e.printStackTrace();
}

return list;
}
 
public int getRows() {
LineNumberReader in = null;
try {
in = new LineNumberReader(new FileReader(new File("log.txt")));
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} 
int count = 0;
String line = null;
try {
while((line = in.readLine()) !=null) {
count++;
}
in.close();
}catch(IOException e) {
e.printStackTrace();
}
return count;
}

 
}
   

 package com.akhil;
 
import java.util.List;
 
import javax.swing.BoundedRangeModel;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.table.AbstractTableModel;
 
public class CustomTableModel extends AbstractTableModel implements
ChangeListener {
 
private String[] headers = { "Record Number", "Data" };
 
private String[][] data;
 
private int fromIndex;
 
private int toIndex;
 
public void stateChanged(ChangeEvent e) {
BoundedRangeModel model = (BoundedRangeModel) e.getSource();
fromIndex = model.getValue();
toIndex = fromIndex + model.getExtent();
 
System.out.println("FromIndex: " + fromIndex);
System.out.println("ToIndex: " + toIndex);
 
OneLinerFileReader reader = new OneLinerFileReader();
List<String> list = reader.getLineInRange(fromIndex, toIndex);
this.data = new String[list.size()][headers.length];
System.out.println("Data Conatins: " + data.length);
for (int i = 0; i < list.size(); i++) {
data[i] = new String[] { "" + i, list.get(i) };
}
 
}
 
public int getColumnCount() {
return headers.length;
}
 
public int getRowCount() {
OneLinerFileReader reader = new OneLinerFileReader();
return reader.getRows();
}
 
public Object getValueAt(int rowIndex, int columnIndex) {
// calulate proper row index to show
return data[rowIndex][columnIndex];
}
 
}   

  package com.akhil;
 
import java.awt.Dimension;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
 
import javax.swing.BoundedRangeModel;
import javax.swing.JFrame;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.JTable;
 
public class TableFrame extends JFrame{

public TableFrame() {
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
buildTable();
setSize(new Dimension(400,300));
setVisible(true);
}
 
private void buildTable() {
JScrollPane scrollPane = new JScrollPane();


CustomTableModel model = new CustomTableModel();
JTable table = new JTable(model);
table.setRowHeight(20);

JScrollBar vScrollBar = scrollPane.getVerticalScrollBar();
BoundedRangeModel vScrollBarModel = vScrollBar.getModel();
vScrollBarModel.setExtent(20);
vScrollBarModel.addChangeListener(model);

scrollPane.setViewportView(table);
getContentPane().add(scrollPane);
}

public static void main(String[] args) {
TableFrame frame = new TableFrame();
}
}
  

Can someone please guide me through this?

regards
Akhil

[Craig Wood]

I ran your log.txt up to 10000 lines and this seems to work okay.

import java.awt.*;
import java.awt.event.*;
import java.util.List;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
 
public class UpdateTest implements ActionListener {
    JTable table;
    final int ROW_COUNT = 1000;
 
    public void actionPerformed(ActionEvent e) {
        String ac = e.getActionCommand();
        int start = Integer.parseInt(ac);
        int end = start + ROW_COUNT-1;
        updateTable(start, end);
    }
 
    private void updateTable(final int start, final int end) {
        Thread thread = new Thread(new Runnable() {
            public void run() {
                OneLinerFileReader reader = new OneLinerFileReader();
                List<String> list = reader.getLineInRange(start, end);
                DefaultTableModel model = (DefaultTableModel)table.getModel();
                int rows = list.size();
                model.setRowCount(rows);
                for(int j = 0; j < rows; j++) {
                    model.setValueAt(String.valueOf(start + j), j, 0);
                    model.setValueAt(list.get(j), j, 1);
                }
            }
        });
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
    }
 
    private JScrollPane getContent() {
        DefaultTableModel model = new DefaultTableModel(ROW_COUNT, 2);
        model.setColumnIdentifiers(new String[] { "line", "data" });
        table = new JTable(model);
        updateTable(0, ROW_COUNT);
        table.setRowHeight(20);
        table.setPreferredScrollableViewportSize(new Dimension(400,240));
        return new JScrollPane(table);
    }
 
    private JPanel getUIPanel() {
        int totalLineCount = new OneLinerFileReader().getRows();
        int rows = table.getRowCount();
        int lines = totalLineCount/rows + ((totalLineCount % rows > 0) ? 1 : 0);
        ButtonGroup group = new ButtonGroup();
        JPanel panel = new JPanel(new GridLayout(0,4));
        for(int j = 0; j < lines; j++) {
            String s = String.format("%d-%d", j*rows, (j+1)*rows-1);
            JRadioButton rb = new JRadioButton(s, j==0);
            rb.setActionCommand(String.valueOf(j*rows));
            rb.addActionListener(this);
            group.add(rb);
            panel.add(rb);
        }
        return panel;
    }
 
    public static void main(String[] args) {
        UpdateTest test = new UpdateTest();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(test.getContent());
        f.getContentPane().add(test.getUIPanel(), "Last");
        f.pack();
        f.setLocation(200,200);
        f.setVisible(true);
    }
}

[Akhil Jain]

Thanks craig.
That seems to work fine, but again, i was achieving the same thing using previous and next button. which was working all fine.
Probalem:
However, i want to handle fetching of records by scrolling the knob down or just clicking on default up and down arrows of vertical scroll bar.
no radio buttons no previous next buttons anywhere with the table. just a message label at top of the table, where it keeps displaying, current record numbers shown to the user.
Can you please show me an example where you just scroll the knob down and it fetches next set of records (if currently visible rows are say, 1-15, then it should fetch records from 16-30 and show it to the user), need to control the unit increment, as well as block increments of the knob.

this way if user, slides the knob to the extreme bottom, he should be able to see actual records in that range from the file(say, file contains 10000 records, then on scrolling to the bottom, will fetch records 9985 - 10,000).
similar is applicable to moving up. so basically i want to do following things. which i am not able to do even with so many tries.

1. Calculate the initial JTable rows, which are visible to the user (row height is assumed to be same for all the rows.)

2. Displaying scroll bar knob size such that, giving a feel to user that, all records are present in table currently. but fetch and display only that much records which are visible to the user.

3. Identifying how down the user has actually moved the slider knob (block increment scenario) and fetching the records within that range, example, if initially, rows displayed are 1 to 20, then on scrolling the knob down say, 40 rows scrolled, then the current rows visible to the user should be 40 to 60.

I am completely, screwed up here.... any help form your side will be a great support craig.

regards,
Akhil

[Akhil Jain]

Can someone please....help me out here........

[Craig Wood]

I copied and ran the code you posted above. It seemed to scroll okay when holding a
scrollBar button but throws exceptions when I click on the scrollBar track. The number
sequences also seem to be off by the table row size. I don't think I could do what you are
asking for. The code I posted is the closest I can come to it.

[Akhil Jain]

NO problem craig...

Thanks for replies.

hey anyways...
here's my version of code with pagination......i was also not able to make it behave in a way i was asking above.

 package com.akhil;
 
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;
import java.util.List;
 
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.ScrollPaneConstants;
import javax.swing.table.DefaultTableModel;
 
public class TablePanel extends JPanel {
 
private JTable table;
 
final int DEFAULT_PAGE_SIZE = 100;
 
private int fromIndex;
 
private int toIndex;
 
private int totalCount;
 
private JLabel currentShowingLabel;
 
/**
 * Create the panel
 */
public TablePanel() {
super();
setLayout(new BorderLayout());
getFileRecordSize();
fromIndex = 0;
toIndex = DEFAULT_PAGE_SIZE + 1;
add(getContent(), BorderLayout.CENTER);
add(getMsgPanel(), BorderLayout.PAGE_END);
}
 
private void getFileRecordSize() {
Thread thread = new Thread(new Runnable() {
public void run() {
OneLinerFileReader reader = new OneLinerFileReader();
totalCount = reader.getRows();
}
});
thread.setPriority(Thread.NORM_PRIORITY);
thread.start();
}
 
private JPanel getMsgPanel() {
final JPanel tableMsgPanel = new JPanel();
currentShowingLabel = new JLabel();
currentShowingLabel.setFont(new Font("", Font.BOLD, 10));
currentShowingLabel.setText("Viewing events: " + fromIndex + " - "
+ (toIndex - 2) + " of " + totalCount);
 
tableMsgPanel.add(currentShowingLabel);
return tableMsgPanel;
}
 
private JScrollPane getContent() {
 
URL urlprev = TablePanel.class.getResource("/images/desc.gif");
ImageIcon prevIcon = new ImageIcon(urlprev);
final JButton prevButton = new JButton(prevIcon);
if (fromIndex <= 0) {
prevButton.setEnabled(false);
}
 
URL urlnext = TablePanel.class.getResource("/images/asc.gif");
ImageIcon nextIcon = new ImageIcon(urlnext);
final JButton nextButton = new JButton(nextIcon);
 
if (toIndex >= totalCount) {
nextButton.setEnabled(false);
} else
nextButton.setEnabled(true);
 
prevButton.addActionListener(new ActionListener() {
public void actionPerformed(final ActionEvent ae) {
toIndex = fromIndex + 1;
fromIndex = toIndex - DEFAULT_PAGE_SIZE - 1;
if (fromIndex <= 0) {
fromIndex = 0;
}
if (fromIndex == 0) {
prevButton.setEnabled(false);
}
if (toIndex != totalCount) {
nextButton.setEnabled(true);
}
 
currentShowingLabel.setText("Viewing events: " + (fromIndex)
+ " - " + (toIndex - 2) + " of " + totalCount);
updateTable(fromIndex, toIndex);
}
});
 
nextButton.addActionListener(new ActionListener() {
public void actionPerformed(final ActionEvent ae) {
fromIndex = toIndex - 1;
if (fromIndex <= 0) {
fromIndex = 0;
}
toIndex = toIndex + DEFAULT_PAGE_SIZE;
if (toIndex == totalCount) {
nextButton.setEnabled(false);
}
if (fromIndex != 0) {
prevButton.setEnabled(true);
}
 
currentShowingLabel.setText("Viewing events: " + (fromIndex)
+ " - " + (toIndex - 2) + " of " + totalCount);
updateTable(fromIndex, toIndex);
}
});
 
DefaultTableModel model = new DefaultTableModel(DEFAULT_PAGE_SIZE, 2);
model.setColumnIdentifiers(new String[] { "Line", "Data" });
table = new JTable(model);
updateTable(fromIndex, toIndex);
table.setRowHeight(20);
table.setPreferredScrollableViewportSize(new Dimension(400, 240));
 
JScrollPane scrollPane = new JScrollPane(table);
// Turn on the scrollbars; otherwise, we won't get our corners.
scrollPane
.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
scrollPane
.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);
 
// Add in the corners (page up/down).
scrollPane
.setCorner(ScrollPaneConstants.UPPER_RIGHT_CORNER, prevButton);
scrollPane
.setCorner(ScrollPaneConstants.LOWER_RIGHT_CORNER, nextButton);
 
return scrollPane;
}
 
private void updateTable(final int start, final int end) {
Thread thread = new Thread(new Runnable() {
public void run() {
OneLinerFileReader reader = new OneLinerFileReader();
List<String> list = reader.getLineInRange(start, end);
// System.out.println("list size: " + list.size());
DefaultTableModel model = (DefaultTableModel) table.getModel();
int rows = list.size();
model.setRowCount(rows);
for (int j = 0; j < rows; j++) {
model.setValueAt(String.valueOf(start + j), j, 0);
model.setValueAt(list.get(j), j, 1);
}
}
});
thread.setPriority(Thread.NORM_PRIORITY);
thread.start();
}
 
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().add(new TablePanel());
f.pack();
f.setLocation(200, 200);
f.setVisible(true);
}
}