paintComponent方法混合了不同的JPanel组件

Question

I'm developing a software which paints 2 different JPanel for my GUI: a score and a mast guitar. The score is a class which extends JPanel and has paintComponent() method like this:

public class PanelPartitura extends JPanel implements MouseListener{
  public void paintComponent(Graphics comp){
    super.paintComponent(comp);
    comp2D = (Graphics2D)comp;
    comp2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);

    paintBackground();
    paintStave();
    paintNotes();

    [...]
  }
}

The mast guitar is a class as well:

public class PanelGuitarra extends JPanel implements MouseListener
  public void paintComponent(Graphics comp){
    super.paintComponent(comp);
    comp2D = (Graphics2D)comp;
    comp2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);

    //Then I call secondary methods to paint it:
    paintBackground();              
    PaintPoints();
  }

  [...]
}

It still works fine. I add the class PanelPartitura to a JScrollPane in order to scroll when it's playing:

partitura = new PanelPartitura();
JScrollPartitura = new JScrollPane(partitura, JScrollPane.VERTICAL_SCROLLBAR_NEVER, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

Both JPanel s mix each others painted components when the software is playing and scrolling. I would like to ask, if somebody has a clue about what on earth is going on? In my opinion:

1. It could be because I separated the painting methods as we've seen above:

    paintBackground(); paintStave(); paintNotes(); 

   then, when the software starts to paint, it paints some parts of the first JPanel ( paintBackground() for example) and then some parts of the mast guitar ( paintBackground() ), then it changes again and the result is a mixture of both.

   I think this is because it mixes different parts every time, I mean it doesn't behave in the same way every time it plays.

   I really don't want this to be happening, so let me ask you: how can I make atomic methods to be sure this wouldn't be the problem?

2. I missunderstood the scroll method. I scroll on this way:

    //the note playing currently position is saved in positionBar positionBar = 150 + 50*PGuitarra.composicion.getAcordeSeleccionado().getPosicionXAcorde(); //horizontalScrollBar is moved to this position PGuitarra.JScrollPartitura.getHorizontalScrollBar().setValue(positionBar); 

Answer 1

I see that your paint methods are not using the same Graphics object (at the JPanel scope). Could that be the reason? And if it is, try passing comp (the Graphics object) as a parameter to paintBackground, paintStave and paintNotes.