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：

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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：

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/*
* 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();
}
}