Why do I have an error when adding states in slick? [closed]

Question

When I was going to create another state I had an error. This is my code:

   public static final int play2 = 3;

and

public Game(String gamename){

      this.addState(new mission(play2));
   }

and

public void initStatesList(GameContainer gc) throws SlickException{
      this.getState(play2).init(gc, this);

   }

I have an error in the addState. above the above code. I don't know where is the problem. But if you want the whole code it is here: package javagame;

import org.newdawn.slick.*;

import org.newdawn.slick.state.*;

public class Game extends StateBasedGame{

   public static final String gamename = "NET FRONT";
   public static final int menu = 0;
   public static final int play = 1;
   public static final int train = 2;
   public static final int play2 = 3;

   public Game(String gamename){
      super(gamename);
      this.addState(new Menu(menu));
      this.addState(new Play(play));
      this.addState(new train(train));
      this.addState(new mission(play2));
   }

   public void initStatesList(GameContainer gc) throws SlickException{
      this.getState(menu).init(gc, this);
      this.getState(play).init(gc, this);
      this.getState(train).init(gc, this);
      this.enterState(menu);
      this.getState(play2).init(gc, this);

   }

   public static void main(String[] args) {

      try{
          AppGameContainer app =new AppGameContainer(new Game(gamename));
          app.setDisplayMode(1500, 1000, false);
          app.start();
      }catch(SlickException e){
         e.printStackTrace();
      }
   }

}
//SYSTEM NETWORKS(C) 2012 NET FRONT

ERROR:

The method addState(GameState) in the type StateBasedGame is not applicable for the arguments (mission)

Answer 1

Edit: Based on the error message I assume, that your class mission is not extending from BasicGameState or GameState, but the addState method expects a GameState object (or an object derived from GameState). Extend BasicGameState in mission and it should work.

Old Answer:

Move the code from the constructor into the init method. The states should be added during init. You can also remove the calls to the states init method, as this is already done by the StateBasedGame class and therefore you would initialize each state twice.

Your init method should look like this:

public void initStatesList(GameContainer gc) throws SlickException{
  this.addState(new Menu(menu));
  this.addState(new Play(play));
  this.addState(new train(train));
  this.addState(new mission(play2));
  this.enterState(play2);
}