JScrollPane 不移动它卡在一个位置

Question

i am Painting some rectangles for class diagram making in a panel and that panel is in a JScrollPane i am updating panel's preferedSize according to size of my rectangle but when painting completes the JScrollPane does not move from its place and i am unable to visit my diagrams

This is Code

        JPanel drawingPane = new DrawingPane();
        drawingPane.setBackground(Color.white);
scroller = new JScrollPane(drawingPane);
    scroller.setPreferredSize(new Dimension(200,200));

add(scroller,BorderLayout.CENTER);

WHAT I AM DOING IN PAINT

 Rectangle rect = new Rectangle(x, y, maxWidth+20, maxHeight+70);

        drawingPane.scrollRectToVisible(rect);
        drawingPane.setPreferredSize(new Dimension(x,y));
        drawingPane.revalidate();   
       g.drawRect(x, y, maxWidth+20, maxHeight+70);

Answer 1

just removed drawingPane.scrollRectToVisible(rect); and everything gone ok