通过J2ME的录音功能实现简易示波器

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

早就有人通过PC声卡的输入(麦克风孔)来做模拟示波器，但是用手机来实现的比较少。用J2ME的MMAPI实现模拟示波器，具体效果稍逊于智能机，因为智能机可以实时读取麦克风输入流，而J2ME还需要有短暂的缓冲构成了阻塞，不过，实现出来玩一下还是足够了。

先贴出效果图：

左图是程序在WTK运行的结果，右图是Audition读取音频输入口的波形，信号源是一个经过信号放大的压力传感器。

程序使用NetBeans + LWUIT类库，接下来贴出全部代码：

import com.sun.lwuit.Command;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.layouts.BorderLayout;
import java.io.ByteArrayOutputStream;
import javax.microedition.media.Manager;
import javax.microedition.media.Player;
import javax.microedition.media.control.RecordControl;

/**
 * @author 张国威
 */
public class Frm_MainMenu extends javax.microedition.midlet.MIDlet implements ActionListener {
    public Form form ;
    private  Command cmdExit = new Command("退出", 1);
    private ThreadReceive threadReceive =new ThreadReceive();//接收数据线程
    private Cmp_Wave cmp_HeartWave=null;
    private Player capturePlayer = null;
    private RecordControl recordControl = null;
    private ByteArrayOutputStream bos = new ByteArrayOutputStream();
    public void startApp() {
        Display.init(this);
        
        form = new Form();//达到全屏的效果
        cmp_HeartWave=new Cmp_Wave(form.getHeight(),form.getWidth());
        form.getStyle().setBgImage(null);//本窗体不需要背景
        form.addCommand(cmdExit);
        form.setCommandListener(this);
        form.setLayout(new BorderLayout());
        //设置画板控件
        form.addComponent(BorderLayout.CENTER,cmp_HeartWave);//添加控件
        form.show();
        try {
          capturePlayer = Manager.createPlayer("capture://audio?rate=8000&bits=8&channels=1");//PCM，8位，8kH
          if (capturePlayer != null) {
            capturePlayer.realize();
            recordControl = (RecordControl) capturePlayer
                .getControl("javax.microedition.media.control.RecordControl");
            if (recordControl == null)
              throw new Exception("No RecordControl available");
            recordControl.setRecordStream(bos);
          } else {
            throw new Exception("Capture Audio Player is not available");
          }
        } catch (Exception e) {}
        threadReceive.start();//开始启动线程
  }
/*
 * byte转为int的函数，因为JAVA的byte范围从-127~127
 */
public static int unsignedByteToInt(byte b) {
    return (int) b & 0xFF;
    }
class ThreadReceive extends Thread {
      private boolean isRuning=true;//默认线程内部while循环可以执行
      public void StopThread()
      {
          isRuning=false;
      }
      public void run(){
          //*************************************************************
          //绘制波形数据
          //*************************************************************
          try {
              capturePlayer.start();
              while(isRuning)
              {
                  recordControl = (RecordControl) capturePlayer.getControl("javax.microedition.media.control.RecordControl");
                  recordControl.setRecordStream(bos);
                  recordControl.startRecord();
                  Thread.sleep(25);//停顿25ms录音
                  recordControl.stopRecord();
                  recordControl.commit();
                  //由于采集频率太高，手机不能完全显示，所以需要通过均值滤波来降低分辨率
                  int Zoom_out=200;//缩小200倍
                  int[] bits=new int[bos.toByteArray().length/Zoom_out];
                  for(int i=0,total=0,index=0;i<bos.toByteArray().length;i++)
                  {
                      total=total+unsignedByteToInt(bos.toByteArray()[i]);
                      if(i%Zoom_out==0 && i!=0)
                      {
                          bits[index]=total/Zoom_out;
                          total=0;
                          index++;
                      }
                  }
                  cmp_HeartWave.UpdateVerticalWave(bits);
                  bos.reset();
              }
              capturePlayer.stop();
              capturePlayer.close();
          } catch (Exception e) {}
      }
  }
    public void actionPerformed(ActionEvent arg0) {
        Command command=arg0.getCommand();
        if(command==cmdExit)//退出程序
            notifyDestroyed();
    }
    protected void pauseApp() {}
    protected void destroyApp(boolean arg0) {}

}

以下代码为画波形图的代码：

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
import com.sun.lwuit.Component;
import com.sun.lwuit.Container;
import com.sun.lwuit.Graphics;
import com.sun.lwuit.Image;
import com.sun.lwuit.layouts.BorderLayout;
/**
 *
 * @author Administrator
 */
public class Cmp_Wave extends Container{
   private Image imgWaveCanvas;//波形图画板，图形画在图像上，再不断地贴图到屏幕
   private int height; //自己定义的画板高度 getHeight()
   private int width; //自己定义的画板宽度 getWidth()
   private int old_xPos=-1;//位置初始化
   private int old_yPos=-1;//位置初始化
   private Component cmpWaveCanvas;//显示波形控件
   private int[] point=null;//每次收到的point数组
   public Cmp_Wave(int canvasHeight,int canvasWidth)
   {
       super.setLayout(new BorderLayout());
       super.addComponent(BorderLayout.CENTER,WaveCanvas(canvasHeight,canvasWidth));//波形显示在中间
   }
   private Component WaveCanvas(int canvasHeight,int canvasWidth)
  {
      height=canvasHeight;
      width=canvasWidth;
      //-------初始化波形画板图像
      imgWaveCanvas=Image.createImage(width, height);
      //-------初始化波形画板控件，在控件上绘制波形画板图像
      cmpWaveCanvas=new Component(){
            public void paint(Graphics g) {
                //在内存中绘制波形图
                Graphics canvas=imgWaveCanvas.getGraphics();
                
                if(point==null)//如果point还没初始化
                    return;//不执行下面语句
                for(int i=0;i<point.length;i++)
                {
                    if(old_xPos>=width //如果xPos超过屏幕宽度
                    || old_xPos==-1) //如果PaintVerticalWave是第一次运行
                    {
                        old_xPos=0;//归零画图
                        old_yPos=height/2;//中心点画图
                        canvas.setColor(0x444444);//设置背景色
                        canvas.fillRect(0, 0, width, height);
                    }
                    int new_yPosPoint=point[i] ;
                    canvas.setColor(0xCCCCCC);//线条色
                    canvas.drawLine(old_xPos,old_yPos,old_xPos+1,new_yPosPoint);
                    old_xPos++;
                    old_yPos=new_yPosPoint;
                }
                //把内存中的波形图画到控件上
                g.drawImage(imgWaveCanvas, 0, 0);
            }
      };      
      cmpWaveCanvas.setFocusPainted(false);
      cmpWaveCanvas.setFocusable(false);
      return cmpWaveCanvas;
  }
   public void UpdateVerticalWave(int []yPos) {
       //更新绘图数组
       int []tmpPos=new int[yPos.length];//临时数组，只取原数组的waveN分之一
       for(int i=0,ii=0;i<tmpPos.length;i++,ii+=1)
           tmpPos[i]=yPos[ii];
       point=tmpPos;
       //重新绘图
       cmpWaveCanvas.repaint();
   }
}