trying to get method working in TableModel

[Alan Shiers]

Hi there,

I've added a new method to my TableModel for JTable which doesn't seem to work as I expected. Note the following code:

public class JLTableModel extends AbstractTableModel
{
  Object[][] data = null;
  String[] headers = null;
  boolean DEBUG = true;
  
  public JLTableModel (Object[][] data, String[] headers)
  {
	  this.data = data;
	  this.headers = headers;
  }
  
  public void removeAllData()
  {
	  int rowCount = data.length;
	  data = new Object[0][0];
	  fireTableRowsDeleted(0, rowCount);
  }

  public void removeRow(int row)
  {
	  Object[][] temp = new Object[data.length - 1][headers.length];
	  int i = 0;
	  int count = 0;
	  for(; i < data.length || i == count; i++)
	  {
		  if(i == row)
			  continue;
		  for(int j = 0; j < headers.length; j++)
		  {			  
		    temp[count][j] = data[i][j];
		  }
		  count++;
	  }
	  
	  data = temp;
	  fireTableRowsDeleted(row, row);
	  //Keep track on whether or not the data is dirty and should be saved
      //before closing the app.
      if(JobLog.isDirty == false)
    	 JobLog.isDirty = true;
	  if (DEBUG) {
          System.out.println("Row of data removed:");
          printDebugData();
      }
  }

What's interesting in this class is that the removeRow(int row) method works fine. Removing a single row with this method does the job. All I'm really doing is replacing the data[][] array with a new instance of Object[][] data. The removeAllData() method does the same thing, only it replaces the data[][] with a new instance of Object[0][0] with no elements. At runtime, if the JTable is populated and I call removeAllData() on the TableModel nothing changes in JTable. The old data is still displaying. What am I dong wrong?

Alan

[Martin Vajsar]

I'm just guessing: try to replace your 17th line with

fireTableRowsDeleted(0, rowCount - 1);

Arguments to fireTableRowsDeleted are inclusive, you're therefore advertising deletion of a row which is actually beyond the last row.

You could also call fireTableDataChanged instead, it tells the table all data (but not the structure) of a table has changed.

A related bug seems to be there: when removing a single row, you don't resize the array, and you use its length to count rows, eg. in removeAllData). I strongly suggest to keep your data in an ArrayList instead. You'll save yourself a lot of hassle with maintaining the array "by hand".

Though it could easily be a list of arrays, I'd create a class to hold data for one row and use a list of instances of this class, but that's a different story.

[Rob Camick]

Use a DefaultTableModel. It already supports this functionality.

You can always look at the source code of this class to see how it works.