Re: Mysterious vanishing/flickering image prblem

"fiziwig" <>
13 Jul 2006 15:16:15 -0700
fiziwig wrote:

I'm trying to draw a grid on a JLayeredPane. My JPane contains a menu,
a toolbar and the layered pane.

What happens is the grid flashes briefly on the screen then disappears.
Then, when I resize the window by dragging the border the grid flashes
and flickers, but ultimately disappears when I stop dragging.

FWIW: Here's the solution I found after trying about 12 different
approaches, including subclassing JComponent (which didn't work right),
and using a glass pane on my JFrame, which put the grid on the caption
bar as well.

Here's what DID work: I replaced my JLayeredPane with this class:

class GridPane extends JLayeredPane {

    private BufferedImage grid;
    private boolean gridShowing;
    private int width,height;

    public GridPane() {
        gridShowing = false;
        width = 1024; // default sizes. The grid image will only be
        height = 768; // once unless the window is resized to bigger
than this

    public void paintComponent(Graphics g) {
        // Override paint component to be able to superimpose grid
        super.paintComponent(g); // paint background
        if (!gridShowing) {
        Graphics2D g2 = (Graphics2D)g;
        g2.drawImage(grid, null, 0, 0);

    public void showGrid(boolean value) {
        gridShowing = value;

        if (grid==null) {

    public void setSize( Dimension d ) {
        super.setSize( d );
    public void setSize( int w, int h ) {
        super.setSize( w, h );
    public void setBounds( int x, int y, int w, int h ) {
        super.setBounds( x, y, w, h );
    private void gridResize() {
        if ((getWidth()>width)||(getHeight()>height)) {
            // window has exceeded max size. redraw grid bigger
    private void makeGrid() {
        // build a grid image at least as big as the window, but no
less than 1024x768
        // This prevents having to create fresh images over and over
while dragging
        // the edge of the window to resize, thus preventing the
garbage collector from
        // having a nervous breakdown.
        int x,y;
        width = getWidth();
        if (width<1024) {
            width = 1024;
        height = getHeight();
        if (height<768) {
            height = 768;
        grid = (BufferedImage)(createImage(width,height));
        Graphics2D gc = grid.createGraphics();
        gc.setColor( new Color(0xd0d0ff));
        for (x=0; x<width; x+=10) {
            gc.drawLine(x, 0, x, height);
        for (y=0; y<height; y+=10) {
            gc.drawLine(0, y, width, y);


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