您如何清空JTable？

Question

I'm trying to dynamically add rows to the JTable, but having hard time with the ArrayIndexOutOfBounds exception. I'm confused because there is no specific explanation why the problem exists and where the problem occures. See below for the code.

ArrayList<ArrayList<String>> matrix = new ArrayList<ArrayList<String>>();
Object[][] data;

Random rand = new Random();

******************** WHEN PRESSING A BUTTON *****************************

matrix.add(new ArrayList<String>()); 
((ArrayList<String>)matrix.get(0)).add("row 0 col " + rand.nextInt(100) );
((ArrayList<String>)matrix.get(0)).add("row 0 col 1");
((ArrayList<String>)matrix.get(0)).add("row 0 col 2");
matrix.add(new ArrayList<String>()); 
((ArrayList<String>)matrix.get(1)).add("row 1 col 0");
((ArrayList<String>)matrix.get(1)).add("row 1 col 1");
((ArrayList<String>)matrix.get(1)).add("row 1 col 2");

data = new Object[matrix.size()][];

for(int i = 0; i < matrix.size(); i++){
    data[i] = matrix.get(i).toArray();
}

table = new JTable(data, new String[]{"A", "B", "C"});
table.setFillsViewportHeight(true);
table.setForeground(Color.WHITE);
table.setBackground(Color.BLACK);
table.setBounds(0, 0, 423, 91);

pnlTable.add(table);
pnlTable.setLayout(null);

table.updateUI();
System.out.println("done");

The problem only occures after pressing 2 or more times on the button. Can anyone help me how to dynamically empty table and add new data in it?

Edit: Here is the Error Log:

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0
    at javax.swing.JTable$1.getValueAt(Unknown Source)
    at javax.swing.JTable.getValueAt(Unknown Source)
    at javax.swing.JTable.prepareRenderer(Unknown Source)
    at javax.swing.plaf.basic.BasicTableUI.paintCell(Unknown Source)
    at javax.swing.plaf.basic.BasicTableUI.paintCells(Unknown Source)
    at javax.swing.plaf.basic.BasicTableUI.paint(Unknown Source)
    at javax.swing.plaf.ComponentUI.update(Unknown Source)
    at javax.swing.JComponent.paintComponent(Unknown Source)
    at javax.swing.JComponent.paint(Unknown Source)
    at javax.swing.JComponent.paintToOffscreen(Unknown Source)
    at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source)
    at javax.swing.RepaintManager$PaintManager.paint(Unknown Source)
    at javax.swing.RepaintManager.paint(Unknown Source)
    at javax.swing.JComponent._paintImmediately(Unknown Source)
    at javax.swing.JComponent.paintImmediately(Unknown Source)
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
    at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
    at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
    at javax.swing.RepaintManager.access$700(Unknown Source)
    at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$000(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

To change a JTable's content, don't re-creating the JTable. Simply create a new TableModel for it such as a DefaultTableModel object or an AbstractTableModel extended class object and set the table's model with your new model via setModel() .

Also, you should avoid null layouts and should never call updateUI unless you're changing the GUI's look and feel.

eg,

import java.awt.BorderLayout;
import java.awt.Color;
import java.util.Arrays;
import java.util.Vector;
import java.util.Random;

import javax.swing.*;
import javax.swing.table.DefaultTableModel;

@SuppressWarnings("serial")
public class TableFoo extends JPanel {
   private static final Vector<String> COLUMN_NAME_VECTOR = new Vector<String>(
         Arrays.asList(new String[] { "A", "B", "C" }));
   private static final int COLUMN_COUNT = COLUMN_NAME_VECTOR.size();
   private JTable table = new JTable();
   private Random rand = new Random();

   public TableFoo() {
      table.setFillsViewportHeight(true);
      table.setForeground(Color.WHITE);
      table.setBackground(Color.BLACK);

      JButton changeData = new JButton(new ChangeDataAction());
      JPanel southPanel = new JPanel();
      southPanel.setBackground(Color.black);
      southPanel.add(changeData);

      setLayout(new BorderLayout());
      add(new JScrollPane(table), BorderLayout.CENTER);
      add(southPanel, BorderLayout.PAGE_END);
   }

   public void changeTableData() {
      Vector<Vector<String>> matrix = new Vector<Vector<String>>();

      int rowCount = rand.nextInt(5) + 3;
      for (int i = 0; i < rowCount ; i++) {
         Vector<String> row = new Vector<String>();
         for (int j = 0; j < COLUMN_COUNT; j++) {
            String rowText = String.format("row %d col %d:   %d", i, j, rand.nextInt(100));
            row.add(rowText );
         }
         matrix.add(row);
      }

      DefaultTableModel model = new DefaultTableModel(matrix,
            COLUMN_NAME_VECTOR);

      table.setModel(model);
   }

   private class ChangeDataAction extends AbstractAction {
      public ChangeDataAction() {
         super("Change Action");
      }

      public void actionPerformed(java.awt.event.ActionEvent arg0) {
         changeTableData();
      };
   }

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

      JFrame frame = new JFrame("TableFoo");
      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();
         }
      });
   }
}

Answer 2

• second from options is remove all elements from XxxTableModel ,

• notice in the case that you remove data from XxxTableModel per one element , then have to start to remove from last element back to the first

for (int i = model.getRowCount() - 1; i > -1; i--) {

• thenafter add new elements to the XxxTableModel

Answer 3

The easiest way to do this is to use TableModel.

DefaultTableModel model = (DefaultTableModel) this.yourTable.getModel();
model.setRowCount(0);

Good Luck!