🚀 go-pugleaf

On Sun, 28 Apr 2002 20:25:05 -0400, PeterH wrote:

BTW, I also noticed the DrawMe class.  It is generally not a very good 
idea to try to draw outside of the update/paint/paintComponent methods.  

If something obscures the drawn area and then it is exposed, the part 
that you have drawn directly will not be repainted.  Also, doing this 
does not play nice with Swing's buffering, so it tends to result in a 
lot of flashing.

I would do three things differently:

1) It will work a lot better if you use a transparent component placed 
above the DrawSizeWavePanel and do the drawing on that.  

2) There is really no need to do the drawing yourself.  JLabel will 
paint strings very nicely.

3) A javax.swing.Timer works very well when you need to do something at 
regular intervals.  It is much simpler than creating a separate thread, 
and more efficient if you have more than one thing going on, since 
Timer will use a single thread for them all.  And finally, Timer will 
run your action on the AWT event thread, and that is where you should 
execute any code that mucks with the UI.

Here is how I would do it:  First create a panel that will move the 
text (JLabel) around.

   class DrawMePanel 
      extends JPanel
   {
      private static final int UNITS = 1;
      private static final int INTERVAL = 25;

      private int x = 0;
      private int y = 0;
      private JLabel label = new JLabel( "Trying this out" );

      private ActionListener updateAction = new ActionListener() {
         public void actionPerformed( ActionEvent event ) {
            if ( x > getWidth() ) {
               Dimension size = label.getSize();
               x = - size.width;
               y += size.height;
            }
            x += UNITS;
            label.setLocation( x, y );
         }
      };

      Timer timer = new Timer( INTERVAL, updateAction );

      public DrawMePanel() {
         setOpaque( false );
         setLayout( null );

         label.setForeground( Color.black );
         label.setLocation( x, y );
         label.setSize( label.getPreferredSize() );
         add( label );
      }

      public void start() {
         timer.start();
      }

      public void stop() {
         timer.stop();
      }
   }

Now place this component above your other component.  You can do this 
using an OverlayLayout.

   DrawSineWavePanel sineWavePanel = new DrawSineWavePanel();
   DrawMePanel drawMePanel = new DrawMePanel();

   JPanel overlayPanel = new JPanel();
   overlayPanel.setLayout( new OverlayLayout( overlayPanel ) );
   overlayPanel.add( drawMePanel );
   overlayPanel.add( sineWavePanel );

   getContentPane().add( overlayPanel, BorderLayout.CENTER );

I think you will find that this runs a *lot* smoother this way.  

-- 
Regards,

John McGrath [TeamB]

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