gamescreen.java

J2ME Game Programming的隋书源代码

/**
 * The central game control class managing: rendering, cycling of world (which
 * includes actors) and other game state.
 */

//#ifdef nokia
//# import com.nokia.mid.ui.FullCanvas;
//#endif
import javax.microedition.lcdui.*;

import net.jscience.math.kvm.MathFP;

//#ifdef nokia
//# 
//# public class GameScreen extends FullCanvas implements Runnable
//# 
//#else

public class GameScreen extends Canvas implements Runnable, CommandListener
//#endif
{
   private static GameScreen theGameScreen;	// "there can be only one..."

   private static int t = 0;
   public static final int NOT_STARTED = t++;	// game state
   public static final int STARTING_UP = t++;   // delay prior to action
   public static final int PLAYING = t++;       // game in progress
   public static final int PAUSED = t++;        // paused
   public static final int DYING = t++;			// we pause after they die
   public static final int GAME_OVER = t++;		// showing "game over..."
   public static final int GAME_DONE = t++;		// game is finished

   private StarAssault theMidlet;
   private int cps;
   private int cyclesThisSecond;
   private long lastCPSTime = 0;

   private int score;

   private World world;
   private Ship playerShip;

   private int leftKeyCode;						// key config (set from app)
   private int rightKeyCode;
   private int fireKeyCode;
   private Command menu;

   // Rendering setup
   private int barWidth;
   private int barHeight;
   private Image osb;
   private Graphics osg;
   private Font defaultFont;
   private int defaultFontHeight;
   private int screenWidth;
   private int screenHeight;
   private int halfScreenWidth;
   private int halfScreenHeight;
   private Image energyBarImage;					// a cached image of the energy bar
   private int lastDrawnBarValue;				// last value we drew the bar at

   // Game state
   private boolean running;						// thread controller
   private int state;
   private long timeStateChanged;
   private int statePriorToPause;
   private int lives;

   // Used to pan the view position based on which way the player is facing.
   private int currentViewPosX;
   private int currentViewPosY;
   private int pixelsPerMSFP = MathFP.div(30, 1000);

   public GameScreen(StarAssault midlet)
   {
      theGameScreen = this;
      theMidlet = midlet;
      running = true;
      setState(NOT_STARTED);

      screenWidth = getWidth();
      screenHeight = getHeight();
      halfScreenWidth = screenWidth / 2;
      halfScreenHeight = screenHeight / 2;

      setKeyBindings();
      lastCycleTime = System.currentTimeMillis();

      //#ifndef nokia
      menu = new Command("Menu", Command.SCREEN, 1);
      addCommand(menu);
      setCommandListener(this);
      //#endif

      initResources();
      // create the game thread
      Thread t = new Thread(this);
      t.start();
   }

   public void setKeyBindings()
   {
      leftKeyCode = StarAssault.getKeyCodeFromNum(theMidlet.getLeftKeyNum());
      rightKeyCode = StarAssault.getKeyCodeFromNum(theMidlet.getRightKeyNum());
      fireKeyCode = StarAssault.getKeyCodeFromNum(theMidlet.getFireKeyNum());
   }

   public final static GameScreen getGameScreen()
   {
      return theGameScreen;
   }

   public final void setState(int newState)
   {
      state = newState;
      timeStateChanged = System.currentTimeMillis();
   }

   public final int getState()
   {
      return state;
   }

   public final int getLevel()
   {
      return world.getLevelNum();
   }

   public void incScore(int i)
   {
      score += i;
   }

   private void initResources()
   {
      //System.out.println("1: freemem=" + Runtime.getRuntime().freeMemory());
      try
      {
         barWidth = screenWidth / 5;
         barHeight = 6;
         energyBarImage = Image.createImage(barWidth, barHeight);

         defaultFont = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_SMALL);
         defaultFontHeight = defaultFont.getHeight();

         // setup the screen
         if (!isDoubleBuffered())
         {
            osb = Image.createImage(screenWidth, screenHeight);
            osg = osb.getGraphics();
            osg.setFont(defaultFont);
         }

         // create the world and playerShip
         world = new World(screenWidth, screenHeight);

         playerShip = new Ship(world);
         playerShip.init(Ship.PLAYER_SHIP, 0, 0);

         world.setPlayerShip(playerShip);
      }
      catch (Exception e)
      {
         System.out.println("App exception: " + e);
         e.printStackTrace();
      }

   }

   private static final int MAX_CPS = 100;
   private static final int MS_PER_FRAME = 1000 / MAX_CPS;
   private long cycleStartTime;
   private long timeSinceStart;
   private long lastCycleTime;
   private long msSinceLastCycle;
   private int panPixelsToMoveFP;

   public void run()
   {
      try
      {
         while (running)
         {
            // remember the starting time
            cycleStartTime = System.currentTimeMillis();
            msSinceLastCycle = System.currentTimeMillis() - lastCycleTime;

            // run the cycle
            if (state == PLAYING)
               world.cycle(msSinceLastCycle);

            if (state == STARTING_UP)
            {
               long timeSinceStateChange = System.currentTimeMillis() -
                       timeStateChanged;
               if (timeSinceStateChange > 3000)
                  setState(PLAYING);
            }

            if (state == GAME_OVER)
            {
               long timeSinceStateChange = System.currentTimeMillis() -
                       timeStateChanged;
               if (timeSinceStateChange > 3000)
               {
                  setState(GAME_DONE);
                  StarAssault.getApp().activateDisplayable(
                          new OnlineScoring(score));
               }
            }

            if (state == DYING)
            {
               long timeSinceStateChange = System.currentTimeMillis() -
                       timeStateChanged;
               if (timeSinceStateChange > 1000)
               {
                  //if (shipsLeft == 0) ...
                  setState(STARTING_UP);
               }
            }

            if (state != PAUSED && state != GAME_DONE && state != NOT_STARTED)
            {
               repaint();

               // update the view pan
               panPixelsToMoveFP += MathFP.mul(pixelsPerMSFP,
                                          MathFP.toFP((int)msSinceLastCycle));

               // Figure out how many whole pixels to move.
               int wholePixels = MathFP.toInt(panPixelsToMoveFP);

               if (wholePixels > 0)
               {
                  // Calculate the ideal position for the view based on the
                  // direction the player's ship is facing.
                  int[] targetViewPos = Actor.getProjectedPos(
                          playerShip.getX(), playerShip.getY(),
                          playerShip.getDirection(), screenWidth / 3);

                  // Adjust the current move slightly towards the ideal view
                  // point.
                  if (currentViewPosX < targetViewPos[0])
                     currentViewPosX += wholePixels;
                  if (currentViewPosX > targetViewPos[0])
                     currentViewPosX -= wholePixels;
                  if (currentViewPosY < targetViewPos[1])
                     currentViewPosY += wholePixels;
                  if (currentViewPosY > targetViewPos[1])
                     currentViewPosY -= wholePixels;

                  // Take away the pixels that were moved.
                  panPixelsToMoveFP = MathFP.sub(panPixelsToMoveFP,
                                                 MathFP.toFP(wholePixels));
               }

               // update the CPS
               if (System.currentTimeMillis() - lastCPSTime > 1000)
               {
                  lastCPSTime = System.currentTimeMillis();
                  cps = cyclesThisSecond;
                  cyclesThisSecond = 0;
               }
               else
                  cyclesThisSecond++;

               lastCycleTime = System.currentTimeMillis();

               // sleep if we've finished our work early
               timeSinceStart = System.currentTimeMillis() - cycleStartTime;

               if (timeSinceStart < MS_PER_FRAME)// && MS_PER_FRAME - timeSinceStart > 5)