通过J2ME的录音功能实现简易示波器
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：
view plaincopy to clipboardprint?
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++)
补充：移动开发 , Android ,
