Implementing the UI elements

MenuList class

This class contains a list of commands to be accessed by the player. Initially it contains New Game and Graphics3D properties, but when the game starts, a new command is added to switch between normal and top views.

1. Create the MenuList class file.

2. Import the required classes.

   import javax.microedition.lcdui.*;
   import javax.microedition.m3g.*;
   

3. Write the below code to create the MenuList class, set it to extend List and to implement CommandListener.

   class MenuList
     extends List
     implements CommandListener
   {
     private final Maze3DMIDlet midlet;
     private boolean gameStarted = false;
     MenuList(Maze3DMIDlet midlet, boolean apiAvailable)
     {
       super("Maze3D", List.IMPLICIT);
       this.midlet = midlet;
       setFitPolicy(List.TEXT_WRAP_ON);
       // in case the 3D API is not available
       if (apiAvailable)
       {
         append("New Game", null);
         append("3D Properties", null);
       }
       // add an exit command
       addCommand(new Command("Exit", Command.EXIT, 0));
       setCommandListener(this);
     }

4. Create a method that indicates if a command event has occurred.

  public void commandAction(Command command, Displayable displayable)
  {
    if (command == List.SELECT_COMMAND)
    {
      int index = getSelectedIndex();
      switch (index)
      {
        case 0:
          //  new game
          midlet.newGame();
          // add more commands the first time the game runs
          if (!gameStarted)
          {
            insert(1, "Top view", null);
            addCommand(new Command("Back", Command.BACK, 0));
            gameStarted = true;
          }
          break;
        case 1:
          if (gameStarted)
          {
            midlet.switchView();
          }
          else
          {
            midlet.show3DProperties();
          }
          break;
        case 2:
          midlet.show3DProperties();
          break;
      }
    }
    else if (command.getCommandType() == Command.BACK)
    {
      midlet.showMain();
    }
    else if (command.getCommandType() == Command.EXIT)
    {
      midlet.quitApp();
    }
  }
  void viewSwitched()
  {
    // switch the labels for normal/top view
    if (getString(1).equals("Top view"))
    {
      set(1, "Normal view", null);
    }
    else
    {
      set(1, "Top view", null);
    }
  }
}

ErrorScreen class

This is the standard screen for handling errors.

1. Create the ErrorScreen class file.

2. Import the required classes.

   import javax.microedition.lcdui.*;

3. Write the below code to create the ErrorScreen class and set it to extend Alert.

   class ErrorScreen
     extends Alert
   {
     private static Image image;
     private static Display display;
     private static ErrorScreen instance = null;
   
   

4. Set up the ErrorScreen object.

     private ErrorScreen()
     {
       super("Error");
       setType(AlertType.ERROR);
       setTimeout(5000);
       setImage(image);
     }
   

5. Create a method to initialize the image and the display.

     static void init(Image img, Display disp)
     {
       image = img;
       display = disp;
     }
   

6. Create a method to show the error screen.

     static void showError(String message, Displayable next)
     {
       if (instance == null)
       {
         instance = new ErrorScreen();
       }
       instance.setTitle("Error");
       instance.setString(message);
       display.setCurrent(instance, next);
     }
   }