Swing simple overlay [duplicate]

Question

I'm in the process of making a 2D game in which a player roams around a maze.

I want to implement some sort of "darkness", even something as simple as a transparent shape around the player surrounded by black, like this:

The problem I've found using Swing is that, while this is possible, it means having to redraw everything, which produces an annoying "flickering" effect every time it happens. Is there a way to make some sort of overlay, or just a good way of doing this in general in Swing? I'm not very experienced with GUI/visual stuff right now so I'd like to stick with Swing if possible.

EDIT: This is my method to paint the background, i.e. the floor, walls and exit:

    public final void paintBG(Graphics g){
    g.setColor(Color.LIGHT_GRAY); // Screen background
    g.fillRect(0, 0, getWidth(), getHeight());
    // Draw the Walls of the maze
    // scalex and y are for scaling images/walls within the maze since I let users specify how big they want the maze
    for (int j = 0; j < this.height; j++, y += scaley) {
        x = 20;
        for (int i = 0; i < this.width; i++, x += scalex) {
            if (!(maze[j][i].northwall.isBroken())) // If the north wall isn't broken
            {
                g.drawImage(walltile, x, y, scalex, scaley / 5, null); // Draw a wall there (image, xpos, ypos, width, height, observer)
            }
            if (!(maze[j][i].eastwall.isBroken())) // etc
            {
                g.drawImage(walltile, x + scalex, y, scalex / 5, scaley, null);
            }
            if (!(maze[j][i].southwall.isBroken())) {
                g.drawImage(walltile, x, y + scaley, scalex, scaley / 5, null);
            }
            if (!(maze[j][i].westwall.isBroken())) {
                g.drawImage(walltile, x, y, scalex / 5, scaley, null);
            }

            if ((j == mazeinfo.getTargetM()) && (i == mazeinfo.getTargetN())) {
                // Draw the exit
                g.drawImage(jeep, x + (scalex / 2), y + (scaley / 2), cx, cy, null);
                g.setColor(Color.LIGHT_GRAY);
                if (maze[j][i].northwall.isEdge()) {
                    // Paint over the edge creating a 'way out'
                    g.fillRect(x, y, scalex, scaley / 4);
                } else if (maze[j][i].eastwall.isEdge()) {
                    g.fillRect(x + scalex, y, scalex / 4, scaley);
                } else if (maze[j][i].southwall.isEdge()) {
                    g.fillRect(x, y + scaley, scalex, scaley / 4);
                } else if (maze[j][i].westwall.isEdge()) {
                    g.fillRect(x, y, scalex / 4, scaley);
                }
            }
        }
    }
}

I then have "paintPlayer" and "paintEnemy" methods to paint those sprites each time they move. The background only gets painted once, at the start.

Answer 1

Possibilities:

• You may be drawing directly in a top level window such as a JFrame. If so, don't draw in the paintComonent method of a JPanel so that you use the automatic double buffering availabe.
• You may be reading in an image from within a painting method, and if so, don't. These methods must paint and paint only and must be blindingly fast.
• You may not be using a BufferedImage in your painting method but creating an image de-novo, and if so, don't. Draw the BufferedImage using Graphics#drawImage(...).
• Perhaps your animation code is off. You may be calling repaint() from within paint or paintComponent, something that should never be done.
• And the possible guesses can go on and on...

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Edit

Your code shows that you may be re-paint the maze with every painting iteration -- don't do this. Instead draw the above into a BufferedImage, and draw that image within your paintComponent method. Then change the BufferedImage if the walls structurally change.

Note that the maze's logical structure (the non-visual data that tells which wall is open, which is closed) should be part of your program's data, and not its code.