layerexample.java

《J2ME Game Programming》随书光盘源代码

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
import java.io.IOException;

/**
 * A very basic midlet to run our GameCanvas example.
 */

public class LayerExample extends MIDlet
{
   private AnotherGameCanvas myCanvas;

   public LayerExample()
   {
      myCanvas = new AnotherGameCanvas();
   }

   protected void startApp() throws MIDletStateChangeException
   {
      Display.getDisplay(this).setCurrent(myCanvas);
      myCanvas.start();
   }

   protected void pauseApp()
   {
   }

   protected void destroyApp(boolean unconditional) throws MIDletStateChangeException
   {
   }
}


/**
 * A class which extends the new MIDP 2 Game Canvas.
 */

class AnotherGameCanvas extends GameCanvas implements Runnable
{
   private boolean running;
   private int x, y;
   private Image orbImage = null;
   private Image backgroundTilesImage = null;

   private Sprite orbSprite;
   private BackgroundLayer backgroundLayer = null;
   private LayerManager layerManager = null;

   public AnotherGameCanvas()
   {
      super(true);

      x = getWidth() / 2;
      y = getHeight() / 2;

      try
      {
         orbImage = Image.createImage("/orb.png");
         backgroundTilesImage = Image.createImage("/pipes.png");
      }

      catch (IOException ioe)
      {
         System.out.println("unable to load image");
      }

      layerManager = new LayerManager();

      // create the orb sprite and add it to the layoutmanager
      orbSprite = new Sprite(orbImage, 16, 16);
      layerManager.append(orbSprite);

      // add the background layer as well
      backgroundLayer = new BackgroundLayer(backgroundTilesImage);
      layerManager.append(backgroundLayer);
   }

   public void start()
   {
      running = true;
      Thread t = new Thread(this);
      t.start();
   }

   public void run()
   {
      Graphics g = getGraphics();

      while (running)
      {
         // handle the state of keys
         int keyStates = getKeyStates();

         if ((keyStates & LEFT_PRESSED) != 0)   x--;
         if ((keyStates & RIGHT_PRESSED) != 0)  x++;
         if ((keyStates & UP_PRESSED) != 0)     y--;
         if ((keyStates & DOWN_PRESSED) != 0)   y++;

         if (x < 0) x = getWidth();
         if (x > getWidth()) x = 0;
         if (y < 0) y = getHeight();
         if (y > getHeight()) y = 0;

         // update the sprite position and animation frame
         orbSprite.setPosition(x, y);
         orbSprite.nextFrame();

         // clear the display
         g.setColor(0x000000);
         g.fillRect(0, 0, getWidth(), getHeight());

         // draw the layers
         layerManager.paint(g, 0, 0);

         // flush the graphics buffer (GameCanvas will take care of painting)
         flushGraphics();

         // sleep a little
         try
         {
            Thread.sleep(5);
         }
         catch (InterruptedException ie)
         {
         }
      }
   }
}

class BackgroundLayer extends TiledLayer
{
   private static final int HORIZONTAL = 1;
   private static final int VERTICAL = 2;
   private static final int CROSS = 3;

   public BackgroundLayer(Image tiles)
   {
      super(20, 20, tiles, 16, 16);

      // draw horizontal lines
      for (int y=0; y < 20; y+=5)
         fillCells(0, y, 19, 1, HORIZONTAL);

      // draw vertical lines
      for (int x=0; x < 20; x+=5)
         fillCells(x, 0, 1, 19, VERTICAL);

      // fill in the cross pieces
      for (int y=0; y < 20; y+=5)
         for (int x=0; x < 20; x+=5)
            setCell(x, y, CROSS);
   }

}