Question

I have JPanel wrapped in JScrollPane and I want the rectangle to be drawn always on the same position = moving with scrollbars wont affect the visibility of the rectangle.

I tried following code:

    public void paintComponent(Graphics g) {
        g.setColor(Color.red);
        g.drawRect(50, (int)getVisibleRect().getY(), 20 , 20);
    }

but it only repaints the rectangle when size of whole JPanel is changed.

Answer 1

IIRC, JScrollPane will try to minimise the amount of redrawing done scrolling, so it wont always cause your component to be updated.

The standard technique is to use a JLayeredPane. Add you JScrollPane to a lower layer, and a non-opaque glass panel component above it. See How to Use a Layered Pane in the Swing tutorial.