1.0 Overview

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The Player's visual presentation and its controls are displayed within the applet's presentation space in the browser window. If you create a Player in a Java application, you are responsible for creating the window to display the Player's components.

Note: While PlayerApplet illustrates the basic usage of a Java Media Player, it does not perform the error handling necessary in a real applet or application. For a more complete sample suitable for use as a template, see "Appendix A: Java Media Applet" on page 37.

2.1 Overview of PlayerApplet

<APPLET CODE=ExampleMedia.PlayerApplet 

WIDTH=320 HEIGHT=300> 
<PARAM NAME=FILE VALUE="Astrnmy.mpg">
</APPLET>

To accomplish this, PlayerApplet extends Applet and implements the ControllerListener interface. PlayerApplet defines five methods:

• init-creates a Player for the file that was passed in through the PARAM tag and registers PlayerApplet as a controller listener so that it can observe media events posted by the Player. (This causes PlayerApplet's controllerUpdate method to be called whenever the Player posts an event.)
  
  
• start-starts the Player when PlayerApplet is started.
  
  
• stop-stops and deallocates the Player when PlayerApplet is stopped.
  
  
• destroy-closes the Player when PlayerApplet is removed.
  
  
• controllerUpdate-responds to Player events to display the Player's components.
  
  

2.2 PlayerApplet Code Listing

PlayerApplet.java:
package ExampleMedia;

import java.applet.*;
import java.awt.*;
import java.net.*;
import javax.media.*;

public class PlayerApplet extends Applet implements ControllerListener {
   Player player = null;
   public void init() {
      setLayout(new BorderLayout());
      String mediaFile = getParameter("FILE");
      try {
         URL mediaURL = new URL(getDocumentBase(), mediaFile);
         player = Manager.createPlayer(mediaURL);
         player.addControllerListener(this);
      } 
      catch (Exception e) {
         System.err.println("Got exception "+e);
      }
   }
   public void start() {
      player.start();
   }
   public void stop() {
      player.stop();
      player.deallocate();
   }
   public void destroy() {
      player.close();
   }
   public synchronized void controllerUpdate(ControllerEvent event) {
      if (event instanceof RealizeCompleteEvent) {
         Component comp;
         if ((comp = player.getVisualComponent()) != null)
            add ("Center", comp); 
         if ((comp = player.getControlPanelComponent()) != null)
            add ("South", comp);	    
         validate();
      }
   }
}

2.3 Initializing the Applet

1. Retrieves the applet's FILE parameter.
2. Uses the FILE parameter to locate the media file and build a URL object that describes that media file.
3. Creates a Player for the media file by calling Manager.createPlayer.
4. Registers the applet as a controller listener with the new Player by calling addControllerListener. Registering as a listener causes PlayerApplet's controllerUpdate method to be called automatically whenever the Player posts a media event. The Player posts media events whenever its state changes. This mechanism allows you to control the Player's transitions between states and ensure that the Player is in a state in which it can process your requests. (For more information, see "Player States" on page 6.)

public void init() {
   setLayout(new BorderLayout());  
   // 1. Get the FILE parameter.
   String mediaFile = getParameter("FILE");
   try {
      // 2. Create a URL from the FILE parameter. The URL 
      // class is defined in java.net.
      URL mediaURL = new URL(getDocumentBase(), mediaFile);
      // 3. Create a player with the URL object.
      player = Manager.createPlayer(mediaURL);
      // 4. Add PlayerApplet as a listener on the new player.
      player.addControllerListener(this);
   } 
   catch (Exception e) {
      System.err.println("Got exception "+e);
   }
}

2.4 Controlling the Player

PlayerApplet implements start to start the Player whenever the applet is started:

public void start() {
   player.start();
}

public void stop() {
   player.stop();
   player.deallocate();
}

When an applet exits, destroy is called to dispose of any resources created by the applet. PlayerApplet overrides destroy to close the Player. Closing a Player releases all of the resources that it's using and shuts it down permanently.

   public void destroy() {
      player.close();
   }

2.5 Responding to Media Events

PlayerApplet responds to one type of event, RealizeCompleteEvent. When the Player posts a RealizeCompleteEvent, PlayerApplet displays the Player's components:

public synchronized void controllerUpdate(ControllerEvent event) 
{
   if (event instanceof RealizeCompleteEvent) {
      Component comp;
      if ((comp = player.getVisualComponent()) != null)
         add ("Center", comp);         
      if ((comp = player.getControlPanelComponent()) != null)
         add ("South", comp);
      validate();
   }

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