JTable: updating cells programitcally

[Peter Simard]

2 of the columns in my JTable hold monetary values ( double).
If the value in cell A changes, then value B should be updated with the result of a calculation performed using the new value in A and the old value in B.
Sort of like a spreadsheet.
I can't seem to set the new value of A for use in a simple calculation.

At present my code is as follows:

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

public class TE extends JFrame
{
  String[] cols = {"VAL_1", "VAL_2", "VAL_3"};
  
  Object[][] filler = {
              {new Double(100.00), new Double(100.00), new Double(100.00)},
              {new Double(200.00), new Double(200.00), new Double(200.00)},
              {new Double(400.00), new Double(400.00), new Double(400.00)}
            };
  JTable table;
      
        
  TE(String title)
    {
      super(title);
      this.setDefaultCloseOperation(EXIT_ON_CLOSE);
      MTM mtm = new MTM(3, cols.length);
      mtm.setColumnIdentifiers(cols);
      
      int nRows = filler.length;
      for(int i = 0; i < nRows; ++i)
        {
          mtm.setValueAt(filler[0][i], 0, i);
          mtm.setValueAt(filler[1][i], 1, i);
          mtm.setValueAt(filler[2][i], 2, i);
        }
    
      
      table = new JTable(mtm);
      table.getColumnModel().getColumn(1).setCellEditor(new SimpleCellEditor());
      table.getColumnModel().getColumn(2).setCellEditor(new SimpleCellEditor());
      
      //table.getColumnModel().getColumn(2).setCellEditor(new SimpleCellEditor());
      JScrollPane jsp = new JScrollPane(table);
      Container c = getContentPane();
      c.add(jsp);
      setSize(300,300);
      setVisible(true);
      
    
      
    }
  class MyMouseListener extends MouseAdapter
    {
      
      public void mouseClicked(MouseEvent e)
      {
        if(e.getClickCount() == 2)
          {
            table.setValueAt("QQQQQQQ", 1,1);
          } 
      } 
    }
class SimpleCellEditor extends AbstractCellEditor implements TableCellEditor, 
                                                             ActionListener
{
  JTextField tf = new JTextField();
  TableModel tm = table.getModel();
  protected EventListenerList listenerList = new EventListenerList();
  protected ChangeEvent changeEvent = new ChangeEvent(this);
  public SimpleCellEditor() 
    {
      super();            
      tf.addMouseListener(new MyMouseListener());
      tf.addActionListener(this);
      
      
    }
public void addCellEditorListener(CellEditorListener listener) {
listenerList.add(CellEditorListener.class, listener);
}
public void removeCellEditorListener(CellEditorListener listener) {
listenerList.remove(CellEditorListener.class, listener);
}
protected void fireEditingStopped() 
  {
    CellEditorListener listener;
    Object[] listeners = listenerList.getListenerList();
    for (int i = 0; i < listeners.length; i++) 
    {
      if (listeners[i] == CellEditorListener.class) 
      {
          listener = (CellEditorListener) listeners[i + 1];
          listener.editingStopped(changeEvent);
      }
    }
  }
protected void fireEditingCanceled() 
{
  CellEditorListener listener;
    Object[] listeners = listenerList.getListenerList();
      for (int i = 0; i < listeners.length; i++) 
  {
      if (listeners[i] == CellEditorListener.class) 
    {
        listener = (CellEditorListener) listeners[i + 1];
        listener.editingCanceled(changeEvent);
    }
  }
}
public void cancelCellEditing() 
  {
    fireEditingCanceled();
  }
public boolean stopCellEditing() 
  {
    fireEditingStopped();
    return true;
  }
public boolean isCellEditable(EventObject event)
  {
    return true;
  }
  public boolean shouldSelectCell(EventObject event) 
  {
  return true;
  }
public Object getCellEditorValue() 
{
  return tf.getText();
}
public Component getTableCellEditorComponent(JTable table, Object value, 
                                       boolean isSelected, int row, int column) 
  {
  
  if(tf.hasFocus() == true)
    {
      tf.setBackground(Color.CYAN);
      
    }
    return tf;
  }
  public void actionPerformed(ActionEvent e)
  {
    int row = table.getSelectedRow();
    int col = table.getSelectedColumn();
    double nVal = 0.00;
    Object currCostVal;
    Object currSellVal;
    Double costVal;
    Double sellVal;
    double newSellVal;
    double currentCost;
    
    if(table.getSelectedColumn() == 1)
    {
      currCostVal = table.getValueAt(row, col+1);
      currSellVal = table.getValueAt(row, col);
      costVal = new Double(currCostVal.toString());
      currentCost = costVal.doubleValue();
      
      sellVal = new Double(currSellVal.toString());
      newSellVal = sellVal.doubleValue();
      nVal = newSellVal*currentCost*100/100;
      System.out.println("Recommended sell-price after change: " + nVal);
    }else if(table.getSelectedColumn() == 2 )
      {
        currCostVal = table.getValueAt(row, col);
        currSellVal = table.getValueAt(row, col-1);
        costVal = new Double(currCostVal.toString());
        currentCost = costVal.doubleValue();
        
        sellVal = new Double(currSellVal.toString());
        newSellVal = sellVal.doubleValue();
        nVal = newSellVal*currentCost*100/100;
        System.out.println("Recommended sell-price after change: " + nVal);
        System.out.println("Cost column selected " + nVal);
      }
  } 
  
}// end simple cell editor
class MTM extends DefaultTableModel
  {
  
    MTM(int rows, int cols)
      {
        super(rows, cols);
          
      }
  } 
  
public static void main(String args[])
  {
    TE te = new TE("Test of table cell update");
    
  }
}

[edited to remove those evil tab characters -ds ]
[ October 18, 2002: Message edited by: Dirk Schreckmann ]

[Bill Liteplo]

I haven't tried your code, but I think there are more conventional ways to solve your problem that are [BOLD]much[/BOLD] simpler.
something like this:

public class TE extends JFrame {
  String[] cols = {"VAL_1", "VAL_2", "VAL_3"};
  // this is the actual data (you can move it elsewhere if you like).  it must be stored in some variable, NOT in the table itself
  Object[][] filler = {
{new Double(100.00), new Double(100.00), new Double(100.00)},
{new Double(200.00), new Double(200.00), new Double(200.00)},
{new Double(400.00), new Double(400.00), new Double(400.00)}
};
  JTable table;
  // this is where the magic happens
  private class MTM extends DefaultTableModel {
    // the model gets the date from the cached values
    public Object getValue(int row, int col) {
      return filler[row][col];
    }
    // this gets called whenever a new value is entered into the table cell
    public void setValue(Object value, int row, int col) {
      // column A, just set the new value in your data cache and set the value of the corresponding cell in column B with the calculated value
      if (col == 0) {
        // do something smarter than a simple cast for better error handling
        Double dValue = (Double)value;        filler[row][col] = (Double)value;
        filler[row][col+1] = doCalc(value);
      }
    }
    // to keep users from directly changing column B
    public boolean isCellEditable(int row, int col) {
      if (col == 1) { // column B
        return false;
      }
      return true;
    }
  } //end MTM
} //end TE

Basic idea:
1. there is some data that are stored in your cache object
2. there is a GUI object (e.g. JTable) that is the interface, but does not store the data
3. you use a model (e.g. TableModel) to control the data and interface between the data cache and the view
I'm sure other people could list numerous resources on this Design Pattern.
Bill