Re: JTable/TableModel undoing

From:
Michael Rauscher <michlmann@gmx.de>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 16 Nov 2006 21:14:17 +0100
Message-ID:
<ejigkb$2si$1@registered.motzarella.org>
Thomas Weidenfeller schrieb:

Deniz Dogan wrote:

Hello!

Does anyone know of a way to provide some sort of undo manager for
JTables or TableModels?


The undo manager is not the problem. Java comes with
//javax.swing.undo.UndoManager//. The problem is that you will have to
implement your own //TableModel// that can talk to the manager by
providing the following.

a) Allows to register //UndoableEditListener//s with the model, so an
//UndoManager// can listen to changes.

b) Allows to de-register //UndoableEditListener//s with the model

c) Generates and fires //UndoableEditEvent//s for each relevant edit,

d) containing an //UndoableEdit// instance describing the edit and
providing the means to undo/redo it.

For bonus points:

e) Make the //UndoableEdit// a //CompoundEdit// for sequences of similar
and related edits (e.g. collapsing multiple single character deletions
into a "word deleted" edit).


Agreed with one exception: to me, e) makes little sense with respect to
tables. Either a cell (or row in the case of additions and deletions)
was updated or it wasn't.

All this is not much fun to implement.


But it's straight-forward if one implements a Decorator for ordinary
TableModels. Of course, in this case row additions/deletions get lost,
but I'd consider it as a starting point.

To substantiate my babbling, I've written a small implementation,
perhaps someone has some use for it ;) [should I GPL it now? - SCNR]

import javax.swing.event.*;
import javax.swing.table.*;
import javax.swing.undo.*;

public class UndoableTableModel extends AbstractTableModel
                                 implements TableModelListener {
     private TableModel delegate;
     private UndoableEditSupport support = new UndoableEditSupport();

     public UndoableTableModel( TableModel delegate ) {
         setDelegate( delegate );
     }

     public void setDelegate( TableModel delegate ) {
         if ( this.delegate != null )
             this.delegate.removeTableModelListener( this );
         this.delegate = delegate;
         if ( this.delegate != null )
             this.delegate.addTableModelListener( this );
         fireTableStructureChanged();
     }

     public Class<?> getColumnClass( int columnIndex ) {
         return delegate.getColumnClass( columnIndex );
     }

     public int getColumnCount() {
         return delegate.getColumnCount();
     }

     public String getColumnName( int columnIndex ) {
         return delegate.getColumnName( columnIndex );
     }

     public int getRowCount() {
         return delegate.getRowCount();
     }

     public Object getValueAt( int rowIndex, int columnIndex ) {
         return delegate.getValueAt( rowIndex, columnIndex );
     }

     public boolean isCellEditable( int rowIndex, int columnIndex ) {
         return delegate.isCellEditable( rowIndex, columnIndex );
     }

     public void setValueAt( Object aValue,
                             int rowIndex, int columnIndex ) {
         Object oldValue = delegate.getValueAt( rowIndex, columnIndex );
         delegate.setValueAt( aValue, rowIndex, columnIndex );
         Object newValue = delegate.getValueAt( rowIndex, columnIndex );
         fireChangeEdit( rowIndex, columnIndex, oldValue, newValue );
     }

     public void addUndoableEditListener( UndoableEditListener l ) {
         support.addUndoableEditListener( l );
     }

     public void removeUndoableEditListener( UndoableEditListener l ) {
         support.removeUndoableEditListener( l );
     }

     public void tableChanged( TableModelEvent e ) {
         TableModelEvent newEvent = new TableModelEvent( this,
                 e.getFirstRow(), e.getLastRow(), e.getColumn(),
                 e.getType() );
         fireTableChanged( newEvent );
     }

     protected void fireChangeEdit( int row, int col, Object oldValue,
                                    Object newValue ) {
         UndoableEdit edit = new TableChangeEdit(row, col,
                 oldValue, newValue);
         support.beginUpdate();
         support.postEdit( edit );
         support.endUpdate();
     }

     private class TableChangeEdit extends AbstractUndoableEdit {
         private int columnIndex;
         private int rowIndex;
         private Object oldValue;
         private Object newValue;

         public TableChangeEdit( int rowIndex, int columnIndex,
                                 Object oldValue, Object newValue ) {
             this.columnIndex = columnIndex;
             this.rowIndex = rowIndex;
             this.oldValue = oldValue;
             this.newValue = newValue;
         }

         public void undo() {
             super.undo();
             delegate.setValueAt( oldValue, rowIndex, columnIndex );
         }

         public void redo() {
             super.redo();
             delegate.setValueAt( newValue, rowIndex, columnIndex );
         }
     }
}

Bye
Michael

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