Implementing the main MIDlet

Maze3DMIDlet class

The Maze3DMIDlet controls the transitions between the different screens. The canvas3D field holds the game, and there are two extra screens for the MenuList and Graphics3DProperties classes. If the MIDlet is stopped or paused, the canvas3D is stopped to kill the Game thread.

1. Create the Maze3DMIDlet class file.

2. Import the required classes.

   import java.util.*;
   import javax.microedition.lcdui.*;
   import javax.microedition.m3g.*;
   import javax.microedition.midlet.*;
   

3. Set Maze3DMIDlet to extend MIDlet. Make sure it includes the creation of a MazeCanvas object, an Image object, and a MenuList object.

   public class Maze3DMIDlet
     extends MIDlet
   {
     private final MazeCanvas canvas3D;
     private final Image logo;
     private MenuList menuList;
   

4. Write the below code to construct the MIDlet.

     //Construct the midlet
     public Maze3DMIDlet()
     {
       logo = makeImage("/logo.png");
       canvas3D = new MazeCanvas(this);
       ErrorScreen.init(logo, Display.getDisplay(this));
     }
   

5. Construct the startApp, pauseApp and destroyApp methods, required for a MIDlet to run.

     public void startApp()
     {
       Displayable current = Display.getDisplay(this).getCurrent();
       if (current == null)
       {
         // check that the API is available
         boolean isApiAvailable =
           (System.getProperty("microedition.m3g.version") != null);
         menuList = new MenuList(this, isApiAvailable);
         if (!isApiAvailable)
         {
           quitApp();
         }
         else
         {
           // Display a splash screen and then the game
           StringBuffer splashText = new StringBuffer("")
             .append(getAppProperty("MIDlet-Name")).
             append("\n").append(getAppProperty("MIDlet-Vendor"));
           Alert splashScreen = new Alert("Maze3D",
             splashText.toString(),
             logo,
             AlertType.INFO);
           splashScreen.setTimeout(3000);
           Display.getDisplay(this).setCurrent(splashScreen, menuList);
         }
       }
       else
       {
         // In case the MIDlet has been hidden
         if (current == canvas3D)
         {
           canvas3D.start();
         }
         Display.getDisplay(this).setCurrent(current);
       }
     }
   
     public void pauseApp()
     {
       canvas3D.stop();
     }
     public void destroyApp(boolean unconditional)
     {
       canvas3D.stop();
     }
   

6. Create the methods used to control the MIDlet and load the required graphics.

     // gets informed when the canvas itself switches the view
     void viewSwitched()
     {
       menuList.viewSwitched();
     }
   
     // starts a new ga,e
     void newGame()
     {
       canvas3D.stop();
       canvas3D.init();
       Display.getDisplay(this).setCurrent(canvas3D);
     }
   
     // shows the menu thread
     void showMenu()
     {
       canvas3D.stop();
       Display.getDisplay(this).setCurrent(menuList);
     }
   
     // quits the app but first stops the game thread
     void quitApp()
     {
       canvas3D.stop();
       notifyDestroyed();
     }
   
   

   The Graphics3D class is a singleton 3D graphics context that can be bound to a rendering target. All rendering is done through the render methods in this class, including the rendering of World objects. The getInstance method is used to retrieve the singleton Graphics3D instance associated with this application. For more information, see Graphics3D and getInstance in the M3G API specification.

        // shows the Graphics3D properties list
        void show3DProperties()
        {
          Graphics3D g3d = Graphics3D.getInstance();
          Display.getDisplay(this).setCurrent(
          new Graphics3DProperties(g3d, this));
        }
   
        // switches the canvas' view
        void switchView()
        {
          canvas3D.switchView();
          canvas3D.start();
          Display.getDisplay(this).setCurrent(canvas3D);
        }
   
        // shows the main canvas
        void showMain()
        {
          canvas3D.start();
          Display.getDisplay(this).setCurrent(canvas3D);
        }
   
        // loads a given image by name
        static Image makeImage(String filename)
        {
          Image image = null;
   
   		  try
          {
            image = Image.createImage(filename);
          }
          catch (Exception e)
          {
            // use a null image instead
          }
          return image;
        }
     }