AppletLauncher.java :  » Swing-Library » thinlet » thinlet » Java Open Source

/* Thinlet GUI toolkit - www.thinlet.com
 * Copyright (C) 2002-2003 Robert Bajzat (robert.bajzat@thinlet.com) */
package thinlet;

import java.applet.*;
import java.awt.*;

/**
 * <code>AppletLauncher</code> is a double buffered applet
 * to launch any <i>thinlet</i> component
 */
public class AppletLauncher extends Applet implements Runnable {
  
  private transient Thinlet content;
  private transient Image doublebuffer;
  
  /**
   * Applet instance is created by the browser or applet viewer
   */
  public AppletLauncher() {
    super(); // for javadoc
  }
  
  /**
   * Called by the browser to inform this applet that it has been loaded into
   * the system, it displays the <i>Loading...</i> label and starts the loader thread
   */
  public void init() {
    setBackground(Color.white); setForeground(Color.darkGray);
    setLayout(new BorderLayout());
    add(new Label("Loading...", Label.CENTER), BorderLayout.CENTER);
    new Thread(this).start();
  }
  
  /**
   * Create a new <i>thinlet</i> instance of the class given as
   * <code>class</code> applet parameter, and show it or the
   * message of the thrown exception. First try a contructor with
   * an applet parameter (thus you get this applet instance e.g. for
   * the parameters of the applet HTML tag), then the empty constructor
   */
  public void run() {
    try {
      Class thinletclass = Class.forName(getParameter("class"));
      try {
        content = (Thinlet) thinletclass.getConstructor(new Class[] {
          Applet.class }).newInstance(new Object[] { this });
      } catch (NoSuchMethodException nsme) {
        content = (Thinlet) thinletclass.newInstance();
      }
      removeAll();
      add(content, BorderLayout.CENTER);
    } catch (Throwable exc) {
      removeAll();
      add(new Label(exc.getClass().getName() + " " +
        exc.getMessage(), Label.CENTER), BorderLayout.CENTER);
    }
    doLayout(); repaint();
  }
  
  /**
   * Clear the double buffer image, the overriden method lays out its
   * components (centers the <i>thinlet</i> component)
   */
  public void doLayout() {
    super.doLayout();
    if (doublebuffer != null) {
      doublebuffer.flush();
      doublebuffer = null;
    }
  }
  
  /**
   * Called by the browser to inform this applet that it should stop its execution,
   * it clears the double buffer image
   */
  public void stop() {
    if (doublebuffer != null) {
      doublebuffer.flush();
      doublebuffer = null;
    }
  }
  
  /**
   * Call the paint method to redraw this component without painting a
   * background rectangle
   */
  public void update(Graphics g) {
    paint(g);
  }

  /**
   * Create a double buffer if needed,
   * the <i>thinlet</i> component paints the content
   */
  public void paint(Graphics g) { 
    if (doublebuffer == null) {
      Dimension d = getSize();
      doublebuffer = createImage(d.width, d.height);
    }
    Graphics dg = doublebuffer.getGraphics();
    dg.setClip(g.getClipBounds());
    super.paint(dg);
    dg.dispose();
    g.drawImage(doublebuffer, 0, 0, this);
  }
  
  /**
   * Called by the browser to inform this applet that it is being reclaimed,
   * it calls the <i>thinlet</i> component's <code>destroy</code> method
   * (its return value is irrelevant)
   */
  public void destroy() {
    content.destroy();
  }
}