hellotoolkit.java

J2ME Game Programming的隋书源代码

import javax.microedition.midlet.MIDletStateChangeException;
import javax.microedition.lcdui.*;

/**
 * An example used to demonstrate how to access, and then display, a property
 * value set within a JAD file.
 *
 * @author Martin J. Wells
 */

public class HelloToolkit extends javax.microedition.midlet.MIDlet
        implements CommandListener
{
   protected Form form;
   protected Command quit;

   /**
    * Constructor for the MIDlet which instantiates the Form object
    * then uses the getAppProperty method to extract the value associated with
    * the "Message" key in the JAD file. It then adds the value as a text field
    * to the Form and sets up a command listener so the commandAction method
    * is called when the user hits the Quit command. Note that this Form is not
    * activated (displayed) until the startApp method is called.
    */
   public HelloToolkit()
   {
      // create a form and add our components
      form = new Form("My Midlet");

      // display our message attribute
      String msg = getAppProperty("Message");
      if (msg != null)
         form.append(msg);

      // create a way to quit
      form.setCommandListener(this);
      quit = new Command("Quit", Command.SCREEN, 1);
      form.addCommand(quit);
   }

   /**
    * Called by the Application Manager when the MIDlet is starting or resuming
    * after being paused. In this example it acquires the current Display object
    * and uses it to set the Form object created in the MIDlet constructor as
    * the active Screen to display.
    * @throws MIDletStateChangeException
    */
   protected void startApp() throws MIDletStateChangeException
   {
      // display our form
      Display.getDisplay(this).setCurrent(form);
   }

   /**
    * Called by the MID's Application Manager to pause the MIDlet. A good
    * example of this is when the user receives an incoming phone call whilst
    * playing your game. When they're done the Application Manager will call
    * startApp to resume. For this example we dont need to do anything.
    */
   protected void pauseApp()
   {
   }

   /**
    * Called by the MID's Application Manager when the MIDlet is about to
    * be destroyed (removed from memory). You should take this as an opportunity
    * to clear up any resources and save the game.  For this example we dont
    * need to do anything.
    * @param unconditional if false you have the option of throwing a
    * MIDletStateChangeException to abort the destruction process.
    * @throws MIDletStateChangeException
    */
   protected void destroyApp(boolean unconditional)
           throws MIDletStateChangeException
   {
   }

   /**
    * The CommandListener interface method called when the user executes
    * a Command, in this case it can only be the quit command we created in the
    * consutructor and added to the Form.
    * @param command
    * @param displayable
    */
   public void commandAction(Command command, Displayable displayable)
   {
      // check for our quit command and act accordingly
      try
      {
         if (command == quit)
         {
            destroyApp(true);

            // tell the Application Manager we're exiting
            notifyDestroyed();
         }
      }

      // we catch this even though there's no chance it will be thrown
      // since we called destroyApp with unconditional set to true.
      catch (MIDletStateChangeException me)
      {
      }
   }
}