How can I change cursor while it does something?

Question

hi, all
following code dosen't change current cursor.
I want to change cursor to wait_cursor while it opens file,
but, it doesn't change cursor at all.
What's problem?
class aClass extends JFrame{
btOpen.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){                
int returnVal = jfcFileDialog.showOpenDialog(SourceEditor.this);
if (returnVal == JFileChooser.APPROVE_OPTION) {
openedFile = jfcFileDialog.getSelectedFile();
setCursor( Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));      
//read openedFile and return text
String fileContent=readSourceFile();
setCursor( Cursor.getPredefinedCursorCursor.DEFAULT_CURSOR));
thank you.

Answer 1

I finally figured it out. You have to set the cursor on the JFrame's GlassPane. The solution was alluded to in the Evaluation section of a couple of bug reports:
http://developer.java.sun.com/developer/bugParade/bugs/4357573.html
http://developer.java.sun.com/developer/bugParade/bugs/4320939.html
There is also some discussion about this in various Forum threads. (Search for topics using "+getGlassPane +setCursor".)
My corrected code follows. With this method, you don't even need to start up a secondary thread to get the cursor to change. I do, however, because I have other UI elements that I want to be updated (such as a sort indicator on my column headings.) I also reduce the priority of the sort thread a bit so my UI gets priority.
Note that I removed the code that tries to remember the original cursor, since, with all the asynchronous execution going on, the wait cursor could actually be the frame's current cursor when this gets executed. If you're not doing a sub-thread as I am, you don't have to worry about this. Also, I have extended JFrame to JFrameBase to handle threading issues and consolidate redundant code (among other things not pictured here). The JFrameBase class definition follows the example code.
Component lTopLevelComponent = JTableSortable.this.getTopLevelAncestor();
final JFrameBase lFrame;
if ( lTopLevelComponent instanceof JFrameBase )
    lFrame = (JFrameBase)lTopLevelComponent;
    lFrame.setFrameCursor( Cursor.getPredefinedCursor( Cursor.WAIT_CURSOR ) );
else
    lFrame = null;
Thread lSortThread = new Thread( "JTableSortable" ) {
    public void run()
        ((SortableTableModel)lModel).sortByColumn( lSortCol, lAscending );
        if ( lFrame != null )
            lFrame.setFrameCursor( Cursor.getPredefinedCursor( Cursor.DEFAULT_CURSOR ) );
lSortThread.setPriority( Math.max( Thread.MIN_PRIORITY, Thread.currentThread().getPriority() - 1 ) );
lSortThread.start();
public class JFrameBase extends JFrame {
public void setFrameCursor( final Cursor aCursor )
    SwingUtilities.invokeLater( new Runnable() {
        public void run()
            getGlassPane().setCursor( aCursor );
            getGlassPane().setVisible( true );