新手必读 详细介绍J2ME的基础知识

// First3DMIDlet.java
package first3d;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class First3DMIDlet extends MIDlet
{
      private First3DCanvas displayable = new First3DCanvas();
      public void startApp()
      {
            Display.getDisplay(this).setCurrent(displayable);
      }

      public void pauseApp() {}

      public void destroyApp(boolean unconditional) {}
}

// First3Dcanvas.java
package first3d;
import javax.microedition.lcdui.*;
import javax.microedition.m3g.*;
import java.util.*;
/**
* 第一个3D程序
*/
public class First3DCanvas extends Canvas implements Runnable
{
      /**World对象*/
      private World myWorld = null;
      /**Graphics3D对象*/
      private Graphics3D g3d = Graphics3D.getInstance();
      /**Camera对象*/
      private Camera cam = null;
      private int viewport_x;
      private int viewport_y;
      private int viewport_width;
      private int viewport_height;
      private long worldStartTime = 0;
      //重绘时间
      private int validity = 0;
     
      public First3DCanvas()
      {
            //启动重绘界面的线程
            Thread thread = new Thread(this);
            thread.start();
            try
            {
                   //导入3D图片
                   myWorld = (World) Loader.load("/swerve.m3g")[0];
                   viewport_x = 0;
                   viewport_y = 0;
                   viewport_width = getWidth();
                   viewport_height = getHeight();
                   cam = myWorld.getActiveCamera();
                   //设置cam对象
                   float[] params = new float[4];
                   int type = cam.getProjection(params);
                   if (type != Camera.GENERIC)
                   {
                          //calculate window aspect ratio
                          float waspect = viewport_width / viewport_height;
                          if (waspect < params[1])
                          {
                                float height = viewport_width / params[1];
                                viewport_height = (int) height;
                                viewport_y = (getHeight() - viewport_height) / 2;
                          }
                          else
                          {
                                float width = viewport_height * params[1];
                                viewport_width = (int) width;
                                viewport_x = (getWidth() - viewport_width) / 2;
                          }
                   }
                   worldStartTime = System.currentTimeMillis();
            }
            catch (Exception e) {}
      }
     
      protected void paint(Graphics g)
      {
            //清除背景
            g.setColor(0x00);
            g.fillRect(0, 0, getWidth(), getHeight());
            //和3D对象绑定
            g3d.bindTarget(g);
            g3d.setViewport(viewport_x, viewport_y, viewport_width, viewport_height);
            long startTime = System.currentTimeMillis() - worldStartTime;
            validity = myWorld.animate((int)startTime);
            try
            {
                   g3d.render(myWorld);
            }
            finally
            {
                   g3d.releaseTarget();
            }
      }

      public void run()
      {
            try
            {
                   while(true)
                   {
                         //重绘图形
                         repaint(viewport_x, viewport_y, viewport_width, viewport_height);
                   }
            }
            catch(Exception e){}
      }
}