I have a JTable that is using a TableColumnModelListener() to detect when the column has been re-sized and I have some code I want to execute in the columnMarginChanged() method.
How do I determine whether the column was re-sized by the user or as a result of other code?
I am thinking I have to start with ChangeEvent.getSource() but I don't know where to go from there.
Thank you.
I can give you one possible approach. I was trying to solve the same problem, because I wanted to serialize information about column widths to disk, so that the next time the table opened up in my application, I could restore the column widths appropriately. Here goes:
Step 1 - Override your JTable and add a boolean property to it
class MyTable extends JTable {
private boolean isColumnWidthChanged;
public boolean getColumnWidthChanged() {
return isColumnWidthChanged;
}
public void setColumnWidthChanged(boolean widthChanged) {
isColumnWidthChanged = widthChanged;
}
}
Step 2 - Add a TableColumnModelListener() to the table
private class TableColumnWidthListener implements TableColumnModelListener
{
@Override
public void columnMarginChanged(ChangeEvent e)
{
/* columnMarginChanged is called continuously as the column width is changed
by dragging. Therefore, execute code below ONLY if we are not already
aware of the column width having changed */
if(!tableObj.hasColumnWidthChanged())
{
/* the condition below will NOT be true if
the column width is being changed by code. */
if(tableObj.getTableHeader.getResizingColumn() != null)
{
// User must have dragged column and changed width
tableObj.setColumnWidthChanged(true);
}
}
}
@Override
public void columnMoved(TableColumnModelEvent e) { }
@Override
public void columnAdded(TableColumnModelEvent e) { }
@Override
public void columnRemoved(TableColumnModelEvent e) { }
@Override
public void columnSelectionChanged(ListSelectionEvent e) { }
}
Step 3 - Add a mouse listener to the table header
private class TableHeaderMouseListener extends MouseAdapter
{
@Override
public void mouseReleased(MouseEvent e)
{
/* On mouse release, check if column width has changed */
if(tableObj.getColumnWidthChanged())
{
// Do whatever you need to do here
// Reset the flag on the table.
tableObj.setColumnWidthChanged(false);
}
}
}
NOTE: In my application, the TableHeaderMouseListener and TableColumnWidthListener classes were private inner classes of my main application class. My main application class held on to a reference of the table being observed. Therefore, these inner classes had access to the table instance. Obviously, depending on your setup, you need to do the appropriate thing to make the table instance available to these other classes. Hope this helps!
Typically you want to be notified of a completed column drag, or a completed column resize. E.g.
interface SGridModel {
public void columnMoved(int oldLocation, int newLocation);
public void columnResized(int column, int newWidth);
}
This isn't pretty but it will do what you want:
class SColumnListener extends MouseAdapter implements TableColumnModelListener {
private final Logger log = Logger.getLogger(getClass());
private final SGridModel model;
private int oldIndex = -1;
private int newIndex = -1;
private boolean dragging = false;
private boolean resizing = false;
private int resizingColumn = -1;
private int oldWidth = -1;
SColumnListener(SGridModel model){
this.model = model;
}
@Override
public void mousePressed(MouseEvent e) {
// capture start of resize
if(e.getSource() instanceof JTableHeader) {
TableColumn tc = ((JTableHeader)e.getSource()).getResizingColumn();
if(tc != null) {
resizing = true;
resizingColumn = tc.getModelIndex();
oldWidth = tc.getPreferredWidth();
} else {
resizingColumn = -1;
oldWidth = -1;
}
}
}
@Override
public void mouseReleased(MouseEvent e) {
// column moved
if(dragging && oldIndex != newIndex) {
model.columnMoved(oldIndex, newIndex);
log.info("column moved: " +oldIndex+" -> "+newIndex);
}
dragging = false;
oldIndex = -1;
newIndex = -1;
// column resized
if(resizing) {
if(e.getSource() instanceof JTableHeader) {
TableColumn tc = ((JTableHeader)e.getSource()).getColumnModel().getColumn(resizingColumn);
if(tc != null) {
int newWidth = tc.getPreferredWidth();
if(newWidth != oldWidth) {
model.columnResized(resizingColumn, newWidth);
log.info("column resized: " +resizingColumn+" -> "+newWidth);
}
}
}
}
resizing = false;
resizingColumn = -1;
oldWidth = -1;
}
@Override
public void columnAdded(TableColumnModelEvent e) {
}
@Override
public void columnRemoved(TableColumnModelEvent e) {
}
@Override
public void columnMoved(TableColumnModelEvent e) {
// capture dragging
dragging = true;
if(oldIndex == -1){
oldIndex = e.getFromIndex();
}
newIndex = e.getToIndex();
}
@Override
public void columnMarginChanged(ChangeEvent e) {
}
@Override
public void columnSelectionChanged(ListSelectionEvent e) {
}
}
add it to the table as follows:
table.getColumnModel().addColumnModelListener(cl);
table.getTableHeader().addMouseListener(cl);
A simpler solution might just be to listen on the mouse release event (which happens only once in this user interaction) and check if the column-sizes changed in the meantime ? I'm using the code below to listen for column reordering and size changes.
getTableHeader().addMouseListener( new MouseAdapter() {
public void mouseReleased(MouseEvent arg0)
{
String colNamesAndSizes = "";
for( int i=0;i<getColumnModel().getColumnCount();i++ ) {
if( i>0 ) colNamesAndSizes += ",";
TableColumn column = getColumnModel().getColumn(i);
colNamesAndSizes += column.getHeaderValue();
colNamesAndSizes += ":";
colNamesAndSizes += column.getWidth();
}
// check if changed, if yes, persist...
}});
You can also add PropertyChangeListener on each TableColumn to capture changes on width and preferredWidth properties.
