Question

I working on a project in which I have to simulate a memory manager and show some memory snapshots. I have created a draw class via examples I have found here in which I override the paintComponet(). Everything draws fine.

I would like to be able to draw a rectangle to represent a memory partition and then overlay another rectangle over top to represent an incoming job (ie Job1 is in this partition3). What seems to occur is that I add the partition first (which will always be the case) and then when I add the job it will sit behind the partition block. Is there a way other than drawing the Job first to shift these after the job is created?

Here is the paint override

@Override public void paintComponent(Graphics g) {

    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;

    // set up rendering to allow anti-aliasing
    g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

    // create the rectangle to represent the memory partition block 
    //  x = address position h = amount of memory (y & w are predefined for the display block)

      Rectangle2D rect = new Rectangle2D.Double(x, y, w, h);    // create the rectangle 
    g2d.setPaint(partColor);                // set it's color
    g2d.fill(rect);                 // fill it in

    // create the transparency for the text
     Composite comp = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, .4f);
     g2d.setComposite(comp);

     // draw the text with color, type and size and center the text in the block created above
     g2d.setPaint(Color.black);
     g2d.setFont(new Font("Tahoma", Font.PLAIN, 12));
     g2d.drawString(text, (int)((w / 2) - (text.length()/2)), (int)h/2);

}

The call to draw is in my window class (this will place the partition in front of the job) but I need to order to be reversed without changing the order of the calls.

    // Draw both Text and Block with transparency
    DrawPartition part1 = new DrawPartition(Color.blue, 0, 0, 110, 100, "part1");
    part1.setBounds(5, 5, 110, 100);
    snapPanel.add(part1);

    DrawJob job1 = new DrawJob(Color.green, 0, 0, 110, 100, "Job 1");
    job1.setBounds(5, 15, 110, 100);
    snapPanel.add(job1);

Answer 1

Is there some reason you can’t do this?

// Draw both Text and Block with transparency
DrawPartition part1 = new DrawPartition(Color.blue, 0, 0, 110, 100, "part1");
part1.setBounds(5, 5, 110, 100);

DrawJob job1 = new DrawJob(Color.green, 0, 0, 110, 100, "Job 1");
job1.setBounds(5, 15, 110, 100);
snapPanel.add(job1);

snapPanel.add(part1);

A more general answer would be to add a z component to each of your rectangles. Then you can loop through your rectangles in the paintComponent method, drawing them in z order.