Question

How to update JTable when data changes

Asked by: jstakk

I'm working on a JTable using a custom table model. The data source for the table model will sometimes change number of columns. If number of rows change, it will be updated, but not columns. I'm calling the fireTableDataChanged() method on the table model.

How do I update number of columns on the JTable?

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Asked On
2009-05-27 at 06:47:32ID24441435
Tags

java

,

swing

,

jtable

,

abstractTableModel

Topics

Java AWT & Swing

,

Java Programming Language

Participating Experts
3
Points
500
Comments
12

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Answers

 

by: gibu_georgePosted on 2009-05-27 at 07:47:23ID: 24483648

You need to use java.swing.table.TableColumnModel to  add columns when ever there is a change also you need to set autoCreateColumnsFromModel  this field to true in the JTable

 

by: CEHJPosted on 2009-05-27 at 08:16:48ID: 24484031

>>I'm calling the fireTableDataChanged() method on the table model.

That should be OK. What's the problem with doing that?

 

by: jstakkPosted on 2009-05-27 at 09:47:33ID: 24485042

>>>>I'm calling the fireTableDataChanged() method on the table model.

>>That should be OK. What's the problem with doing that?

I don't know if there is something wrong with that. My problem is how to update the table to show the new colomns or remove the ones missing.

Could someone explain how I  use TableColumnModel?

 

by: CEHJPosted on 2009-05-27 at 10:07:42ID: 24485199

It would happen automatically if you were using an existing model, such DefaultTableModel. Do you really need your own TableModel?

If so, you need to alter the behaviour of http://java.sun.com/javase/6/docs/api/javax/swing/table/TableModel.html#getColumnCount() and any other column-oriented methods accordingly

 

by: Thomas4019Posted on 2009-05-27 at 10:23:59ID: 24485442

Could you post your code for the model?

 

by: jstakkPosted on 2009-05-27 at 10:39:34ID: 24485603

Here is my code.

Thanks for helping me.

public class MyTableModel extends AbstractTableModel implements Observer
{
 
	private static final long	serialVersionUID	= -5926837260794060766L;
	private CustomData			data;
 
	public MyTableModel( CustomData data ) {
		this.data = data;
		data.addObserver( this );
	}
 
	@Override
	public int getColumnCount() {
		double[][] vector = data.getVector();
		return vector[0].length;
	}
 
	@Override
	public int getRowCount() {
		return data.getVector().length;
	}
 
	@Override
	public Object getValueAt( int row, int column ) {
		double[][] vector = data.getVector();
		if (vector != null) return vector[row][column];
 
		else return 0.0;
	}
 
	@Override
	public void update( Observable o, Object arg ) {
		fireTableDataChanged();
	}
 
}

                                              
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by: CEHJPosted on 2009-05-27 at 10:49:42ID: 24485693

You should be OK with that - it should return the correct column count

 

by: Thomas4019Posted on 2009-05-27 at 10:54:22ID: 24485738

Fire this method when a large change occurs in your data (such as a new column)

fireTableStructureChanged()

 

by: Thomas4019Posted on 2009-05-27 at 10:57:14ID: 24485765

So basically when you change a column you will need to change

fireTableDataChanged();

instead of

fireTableStructureChanged()

both are inherited as part of AbstractTableModel

 

by: Thomas4019Posted on 2009-05-27 at 10:58:06ID: 24485776

Oops got those backwards, fireTableStructureChanged() when you change a column.

 

by: jstakkPosted on 2009-05-27 at 10:58:42ID: 24485783

That did it... now it works. Thanks.

 

by: CEHJPosted on 2009-05-27 at 11:00:03ID: 24485794

>>Oops got those backwards, fireTableStructureChanged() when you change a column.

Yes, that's right

20120131-EE-VQP-002

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