Member Avatar for staneja

I am trying to display an Image using applet. Image is updated after every 4 seconds so i want my applet to show updated image.I am not sure where
i should load the image i have tried to load it in the init() method as well as in "start" method but it didnt workd out for me.Can anybody please help me with this

  • 1 Contributor
  • 1 Reply
  • 109 Views
  • 2 Days Discussion Span
  • Latest Post Latest Post by staneja

Dani AI

Generated

A simple, reliable pattern is to treat the image refresh as a background task and make sure you actually fetch a fresh copy (rather than relying on whatever the Toolkit/browser cache is holding). The workaround shown later in this thread can make a stale image appear to update on some systems, but it is brittle. A robust approach:

  • Load the image off the Event Dispatch Thread (start a thread in start() and stop it in stop()).
  • Fetch the image with caching disabled (either add a cache-busting query string or open a URLConnection with setUseCaches(false) and read via ImageIO).
  • Replace the applet image reference and call repaint() when the new image is ready.
  • Avoid flicker by double-buffering or overriding update() to call paint().

Example (concept only — not the workaround posted by ):

private BufferedImage loadFreshImage(String name) throws IOException {
    URL url = new URL(getCodeBase(), name + "?_=" + System.currentTimeMillis());
    URLConnection conn = url.openConnection();
    conn.setUseCaches(false);
    try (InputStream in = conn.getInputStream()) {
        return ImageIO.read(in);
    }
}

Example refresh loop:

public void run() {
    while (running) {
        currentImage = loadFreshImage("graph.png");
        repaint();
        Thread.sleep(4000);
    }
}

Draw using an offscreen BufferedImage (or at least override update(Graphics g) to call paint(g)), so the screen does not flash while the image is replaced.

Troubleshooting tips: verify the server actually serves a new file (open the image URL in a browser), check HTTP cache headers, and call image.flush() before discarding an old Image if you must reuse the same object reference. Avoid relying on forced GC or short sleeps as a fix; they mask the underlying caching/drawing issues. Note that Java applets are deprecated in modern browsers — consider migrating if long-term support is required.

Member Avatar for staneja

Hi , I added the follwing code in my applet and it solved my problem

try{ 
    // Step 1: get a Runtime object 
    Runtime r = Runtime.getRuntime(); 
    r.gc(); 
    Thread.sleep(1);

    }catch(InterruptedException xx){ xx.getMessage(); };


}
Edited by Reverend Jim because: Fixed formatting
Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.