[samkri]

Good evening!

Why my main menu doesn't work?

Sun WTK gives the following errors:
-cannot resolve symbol : method destroyApp (boolean)

-cannot resolve symbol : method notifyDestroyed ()

public class Menu extends List implements CommandListener
{
	private GameMIDlet midlet;	// MIDlet
	private Game game;		// Game screen
	private List list;
	private Instructions inst;
	private About about;
	private Command select = new Command("", Command.ITEM, 1);
	private Command exit   = new Command("", Command.EXIT, 1);

	public Menu(GameMIDlet midlet)
	{
		super("Game", Choice.IMPLICIT);
		this.midlet = midlet;
		append("New game", null);
		append("Instructions", null);
		append("About", null);
		append("Exit", null);
		addCommand(select);
		addCommand(exit);
		setCommandListener(this);
	}

	public void commandAction(Command c, Displayable dl)
	{
		if (dl == list && c == List.SELECT_COMMAND)
		{
			switch (list.getSelectedIndex())
			{
				// Start game
				case 0:
				game = new Game(midlet, this);
				midlet.setDisplayable(game);
				break;

				// Instructions
				case 1:
				inst = new Instructions(midlet, this);
				midlet.setDisplayable(inst);
				break;

				// About
				case 2:
				about = new About(midlet, this);
				midlet.setDisplayable(about);
				break;

				// Exit	
				case 3:
				destroyApp(true);
				notifyDestroyed();
				break;
				
			}
		}
	}
}

[shmoove]

Because destroyApp() and notifyDestroyed() are methods of the MIDlet class, so it should be:

midlet.destroyApp(true);
midlet.notifyDestroyed();

shmoove

[samkri]

Thanks.
Now main menu appears to the screen but you can't select anything from the list. When pressing 'select' nothing happens and same thing when pressing 'exit'.

[kisember]

Take a look at the first condition in the commandAction method. The list still null so the expression is always false.

Also note (quote from MIDP API javadoc):

IMPLICIT List can be used to construct menus by placing logical commands to elements. In this case no application defined Commands have to be attached. Application just has to register a CommandListener that is called when user "selects".

[samkri]

So how I have to change the code? :)

[shmoove]

Like kisember said, the variable called list is null, you never assigned anything to it (and I seriously doubt that you even need that variable). So that first if statement in commandAction will always be false. Unless the Menu class is a CommandListener for other screens there is no need to test if dl == list, and if there was a need then you would probably want to compare to this and not to list.

shmoove

[samkri]

It must be like this.
Am I right?

public void commandAction(Command c, Displayable dl)
{
   if (c == List.SELECT_COMMAND)
   {
      switch (list.getSelectedIndex())
      {
         // Start game
         case 0:
         game = new Game(midlet, this);
         midlet.setDisplayable(game);
         break;

         // Instructions
         case 1:
         inst = new Instructions(midlet, this);
         midlet.setDisplayable(inst);
         break;

         // About
         case 2:
         about = new About(midlet, this);
         midlet.setDisplayable(about);
         break;

         // Exit	
         case 3:
         destroyApp(true);
         notifyDestroyed();
         break;
         }
      }
}

[shmoove]

Yes, and also as Kisember said, adding a select command yourself is unnecessary because an IMPLICIT List will do it for you.

shmoove

[samkri]

And I don't need to use these lines :

 
if (c == List.SELECT_COMMAND)
{
      switch (list.getSelectedIndex())

Am I correct?

[shmoove]

Comparing to the List.SELECT_COMMAND is probably necessary since you have that exit command there and that's how you would tell the difference between someone choosing a command from the menu and someone pressing the exit command (although you are not handling that exit command, ie, if c == exit).
And in the switch statement what you don't need is that "list" variable (again). Since it's a member method of your class that extends List, you can just do getSelectedIndex() directly.
So basically what you'd have is:

public void commandAction(Command c, Displayable dl)
{
   if (c == List.SELECT_COMMAND)
   {
      // an item from the list was chosen,
      // to know which one, we do:
      switch (getSelectedIndex())
      {
          // handle list items according to index
       }
    }
    else if (c == exit) {
      // the exit command was pressed
      // (not the exit item from the list but the
      // exit command you added
    }
}

shmoove

[samkri]

Thank you very much 'shmoove' and 'kisember' but I still have few problems :)

When I'm trying to choose from the menu 'New game', 'Instructions', 'About' or 'Exit' nothing happens.

Below is the example:

Menu.java :

import javax.microedition.lcdui.*;

public class Menu extends List implements CommandListener
{
   private GameMIDlet midlet;
   private Game game;
   private Command select = new Command("Select",  Command.ITEM, 1);
   private Command exit = new Command("Exit", Command.EXIT, 1);

   public Menu(GameMIDlet midlet)
   {
      super("Game", Choice.IMPLICIT);
      this.midlet = midlet;
      append("New game", null);
      append("Instructions", null);
      append("About", null);
      append("Quit", null);
      addCommand(exit);
      addCommand(select);
      setCommandListener(this);
   }

public void commandAction(Command c, Displayable dl)
{
   if (c == List.SELECT_COMMAND)
   {
       switch (getSelectedIndex())
      {
         // Start game
         case 0:
         game = new Game(midlet, this);
         midlet.setDisplayable(game);
         break;

         // Instructions screen
         case 1:
         inst = new Instructions(midlet, this);
         midlet.setDisplayable(inst);
         break;

         // About screen
         case 2:
         about = new About(midlet, this);
         midlet.setDisplayable(about);
         break;
      }
   }
   else if (c == exit)
   {
       try 
       {
           midlet.destroyApp(true);
           midlet.notifyDestroyed();
       }
       catch (Exception e)
       {
           System.out.println("e");
       }
    }
  }
}

Instructions.java :

import javax.microedition.lcdui.*;

public class Instructions extends Form implements CommandListener
{
   private GameMIDlet midlet;
   private Menu menu;
   private Command backCommand = new Command("Back",   Command.EXIT, 1);

   public Instructions(GameMIDlet midlet, Menu menu)
   {
      super("Instructions");
      this.midlet = midlet;
      this.menu = menu;
      StringItem item = new StringItem(null,
      "Instructions...........");
      append(item);
      addCommand(backCommand);
      setCommandListener(this);
   }

   public void commandAction(Command c, Displayable d)
   {
      if (c == backCommand)
      {
         midlet.setDisplayable(menu);
         return;
      }
   }
}

What is the problem?

[samkri]

I solved my problem and now main menu works!