gamescreen.java

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import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class GameScreen extends GameCanvas implements Runnable, CommandListener {
  private static final int MILLIS_PER_TICK = 50;

  private Eliminator midlet;  // Hold the Main Midlet
  private Settings settings;  // Hold Game Settings
  private Score score;        // Hold Game Score
  private Command backCommand = new Command("Back", Command.BACK,1);
  private GameMap gameMap;

  private boolean isPlay;   // Game Loop runs when isPlay is true
  private int width;        // To hold screen width
  private int height;       // To hold screen height

  private int scnViewWidth; // Hold Width Screen View Port
  private int scnViewHeight; // Hold Height Screen View Port

  private Thread gameThread = null;

  // Layer Manager to manager background (terrain)
  private LayerManager layerManager;

  // TiledLayer - Terrain
  private TiledLayer terrain;
  private int terrainScroll;   // Hold Y position for scrolling

  // Constructor and initialization
  public GameScreen(Eliminator midlet,Settings settings,Score score) throws Exception {
    super(true);
    this.midlet = midlet;
    addCommand(backCommand);
    setCommandListener(this);

    width = getWidth();  // get screen width
    height = getHeight();  // get screen height
    scnViewWidth = width; // Set View Port width to screen width
    scnViewHeight = height; // Set View Port height to screen height

    isPlay = true;   


    gameMap = new GameMap(scnViewHeight);
    terrain = gameMap.getTerrain();
    
    layerManager = new LayerManager();
    layerManager.append(terrain);

  }

  // Start thread for game loop
  public void start() {
    gameThread = new Thread(this);
    gameThread.start();
  }

  // Stop thread for game loop
  public void stop() {
    gameThread = null;
  }

  // Main Game Loop
  public void run() {
    Graphics g = getGraphics();

    Thread currentThread = Thread.currentThread();

    try {
      while (currentThread == gameThread) {
      	long startTime = System.currentTimeMillis();
      	if (isShown()) {
      	  if (isPlay) {
      	    tick();
      	  }
          render(g);
      	}
      	long timeTake = System.currentTimeMillis() - startTime;
      	if (timeTake < MILLIS_PER_TICK) {
      	  synchronized (this) {
      	    wait(MILLIS_PER_TICK - timeTake);
      	  }
      	} else {
      	  currentThread.yield();
      	}
      }
    } catch (InterruptedException ex) {
      // won't be thrown
    }

  }

  // Handle dynamic changes to game including user input
  public void tick() {
    // Scroll Terrain	
    gameMap.scrollTerrain();   
  }

  public void commandAction(Command c, Displayable d) {
    if (c == backCommand) {
      midlet.mainMenuScreenShow(null);
    }
  }

  // Method to Display Graphics
  private void render(Graphics g) {

    // Set Background color to beige
    //g.setColor(0xF8DDBE);
    g.setColor(gameMap.getGroundColor());
    g.fillRect(0,0,width,height);
    g.setColor(0x0000ff);

    // Get Current Map 
    terrain = gameMap.getTerrain();

    // LayerManager Paint Graphics
    layerManager.paint(g,0,0);

    flushGraphics();
  }
}