Knowledge Base Nr: 00136 appletBildNachladen.java - http://www.swe-kaiser.de

Downloads:

java: http kommunikation eines java-applets mit dem server über port 80
(durch firewall) - z.b. nachladen von bildern

  
class k_LiveCanvas extends Canvas
{
  k_LiveCam2 liveCam = null;

  public k_LiveCanvas(k_LiveCam2 lc)
  {
    liveCam = lc;
  }

  public void mypaint()
  {
  	Graphics g = getGraphics();
  	paint(g);
  }

  public void paint(Graphics g)
  {
    if (liveCam.liveImg != null)
    {
      if (liveCam.tracker.checkID(0))
      {
        g.drawImage(liveCam.liveImg, 0, 0, this);
      }
    }
  }
}

public class k_LiveCam2 extends java.applet.Applet implements Runnable
{
...
  Image liveImg = null;
  MediaTracker tracker = null;
  k_LiveCanvas picCanvas = null;
...

  public void init ()
  {
...
    //canvas
    picCanvas = new k_LiveCanvas(this);
    picCanvas.setBackground(Color.white);
    picCanvas.setSize(768,576);
    add(picCanvas);

    tracker = new MediaTracker(this);
 }

  boolean doSingleDisplay()
  {
    try
    {
      //avoid caching
      if (liveImg != null)
        liveImg.flush();

      try
      {
        URL req = new URL("http://" + p_host +"/cgi-bin/getLivePic.pl?picsize=1");
        //das aufgerufene script muss direkt ein bild zurückgeben
        //z.b über den location header (location: /images/picture.jpg)

        liveImg = getImage(req);
        tracker.addImage(liveImg, 0);
        tracker.waitForID(0);
      }
      catch(InterruptedException e)
      {
      }

      picCanvas.mypaint();   //verhindert flackern (unterdrückt das löschen des hintergrunds)
    }
    catch ( IOException e )
    {
    }

    return true;
  }

  public void run ()   //thread for cyclic refreshing
  {
    while ( runflag )
    {
      if (isCyclic)
      {
          boolean bValid = doSingleDisplay();
      }

      mysleep(50);  //give other threads a chance
    }
  }

}