Android提高之模拟信号示波器的实现

前面简单地介绍了android程序开发中audiorecord和audiotrack的使用，这次再结合surfaceview实现一个android版的手机模拟信号示波器。最近物联网炒得很火，作为手机软件开发者，如何在不修改手机硬件电路的前提下实现与第三方传感器结合呢？麦克风就是一个很好的adc接口，通过麦克风与第三方传感器结合，再在软件里对模拟信号做相应的处理，就可以提供更丰富的传感化应用。

先来看看本文程序运行的效果图(屏幕录像截图的速度较慢，真机实际运行起来会很流畅)：

本文程序使用8000hz的采样率，对x轴方向绘图的实时性要求较高，如果不降低x轴的分辨率，程序的实时性较差，因此程序对x轴数据缩小区间为8倍～16倍。由于采用16位采样，因此y轴数据的高度相对于手机屏幕来说也偏大，程序也对y轴数据做缩小，区间为1倍～10倍。在surfaceview的ontouchlistener方法里加入了波形基线的位置调节，直接在surfaceview控件上触摸即可控制整体波形偏上或偏下显示。

main.xml源码如下：

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" android:layout_width="fill_parent"
 android:layout_height="fill_parent">
 <linearlayout android:id="@+id/linearlayout01"
 android:layout_height="wrap_content" android:layout_width="fill_parent"
 android:orientation="horizontal">
 <button android:layout_height="wrap_content" android:id="@+id/btnstart"
  android:text="开始" android:layout_width="80dip"></button>
 <button android:layout_height="wrap_content" android:text="停止"
  android:id="@+id/btnexit" android:layout_width="80dip"></button>
 <zoomcontrols android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/zctlx"></zoomcontrols>
 <zoomcontrols android:layout_width="wrap_content"
  android:layout_height="wrap_content" android:id="@+id/zctly"></zoomcontrols>
 </linearlayout>
 <surfaceview android:id="@+id/surfaceview01"
 android:layout_height="fill_parent" android:layout_width="fill_parent"></surfaceview>
</linearlayout>

clsoscilloscope.java是实现示波器的类库，包含audiorecord操作线程和surfaceview绘图线程的实现，两个线程同步操作，代码如下：

package com.testoscilloscope;
import java.util.arraylist;
import android.graphics.canvas;
import android.graphics.color;
import android.graphics.paint;
import android.graphics.rect;
import android.media.audiorecord;
import android.view.surfaceview;
public class clsoscilloscope {
 private arraylist<short[]> inbuf = new arraylist<short[]>();
 private boolean isrecording = false;// 线程控制标记
 /**
 * x轴缩小的比例
 */
 public int ratex = 4;
 /**
 * y轴缩小的比例
 */
 public int ratey = 4;
 /**
 * y轴基线
 */
 public int baseline = 0;
 /**
 * 初始化
 */
 public void initoscilloscope(int ratex, int ratey, int baseline) {
 this.ratex = ratex;
 this.ratey = ratey;
 this.baseline = baseline;
 }
 /**
 * 开始
 * 
 * @param recbufsize
 *      audiorecord的minbuffersize
 */
 public void start(audiorecord audiorecord, int recbufsize, surfaceview sfv,
  paint mpaint) {
 isrecording = true;
 new recordthread(audiorecord, recbufsize).start();// 开始录制线程
 new drawthread(sfv, mpaint).start();// 开始绘制线程
 }
 /**
 * 停止
 */
 public void stop() {
 isrecording = false;
 inbuf.clear();// 清除
 }
 /**
 * 负责从mic保存数据到inbuf
 * 
 * @author gv
 * 
 */
 class recordthread extends thread {
 private int recbufsize;
 private audiorecord audiorecord;
 public recordthread(audiorecord audiorecord, int recbufsize) {
  this.audiorecord = audiorecord;
  this.recbufsize = recbufsize;
 }
 public void run() {
  try {
  short[] buffer = new short[recbufsize];
  audiorecord.startrecording();// 开始录制
  while (isrecording) {
   // 从mic保存数据到缓冲区
   int bufferreadresult = audiorecord.read(buffer, 0,
    recbufsize);
   short[] tmpbuf = new short[bufferreadresult / ratex];
   for (int i = 0, ii = 0; i < tmpbuf.length; i++, ii = i
    * ratex) {
   tmpbuf[i] = buffer[ii];
   }
   synchronized (inbuf) {//
   inbuf.add(tmpbuf);// 添加数据
   }
  }
  audiorecord.stop();
  } catch (throwable t) {
  }
 }
 };
 /**
 * 负责绘制inbuf中的数据
 * 
 * @author gv
 * 
 */
 class drawthread extends thread {
 private int oldx = 0;// 上次绘制的x坐标
 private int oldy = 0;// 上次绘制的y坐标
 private surfaceview sfv;// 画板
 private int x_index = 0;// 当前画图所在屏幕x轴的坐标
 private paint mpaint;// 画笔
 public drawthread(surfaceview sfv, paint mpaint) {
  this.sfv = sfv;
  this.mpaint = mpaint;
 }
 public void run() {
  while (isrecording) {
  arraylist<short[]> buf = new arraylist<short[]>();
  synchronized (inbuf) {
   if (inbuf.size() == 0)
   continue;
   buf = (arraylist<short[]>) inbuf.clone();// 保存
   inbuf.clear();// 清除
  }
  for (int i = 0; i < buf.size(); i++) {
   short[] tmpbuf = buf.get(i);
   simpledraw(x_index, tmpbuf, ratey, baseline);// 把缓冲区数据画出来
   x_index = x_index + tmpbuf.length;
   if (x_index > sfv.getwidth()) {
   x_index = 0;
   }
  }
  }
 }
 /**
  * 绘制指定区域
  * 
  * @param start
  *      x轴开始的位置(全屏)
  * @param buffer
  *      缓冲区
  * @param rate
  *      y轴数据缩小的比例
  * @param baseline
  *      y轴基线
  */
 void simpledraw(int start, short[] buffer, int rate, int baseline) {
  if (start == 0)
  oldx = 0;
  canvas canvas = sfv.getholder().lockcanvas(
   new rect(start, 0, start + buffer.length, sfv.getheight()));// 关键:获取画布
  canvas.drawcolor(color.black);// 清除背景
  int y;
  for (int i = 0; i < buffer.length; i++) {// 有多少画多少
  int x = i + start;
  y = buffer[i] / rate + baseline;// 调节缩小比例，调节基准线
  canvas.drawline(oldx, oldy, x, y, mpaint);
  oldx = x;
  oldy = y;
  }
  sfv.getholder().unlockcanvasandpost(canvas);// 解锁画布，提交画好的图像
 }
 }
}

testoscilloscope.java是主程序，控制ui和clsoscilloscope，代码如下：

package com.testoscilloscope;
import android.app.activity;
import android.graphics.color;
import android.graphics.paint;
import android.media.audioformat;
import android.media.audiorecord;
import android.media.mediarecorder;
import android.os.bundle;
import android.view.motionevent;
import android.view.surfaceview;
import android.view.view;
import android.view.view.ontouchlistener;
import android.widget.button;
import android.widget.zoomcontrols;
public class testoscilloscope extends activity {
  /** called when the activity is first created. */
 button btnstart,btnexit;
 surfaceview sfv;
  zoomcontrols zctlx,zctly;
  
  clsoscilloscope clsoscilloscope=new clsoscilloscope();
  
 static final int frequency = 8000;//分辨率
 static final int channelconfiguration = audioformat.channel_configuration_mono;
 static final int audioencoding = audioformat.encoding_pcm_16bit;
 static final int xmax = 16;//x轴缩小比例最大值,x轴数据量巨大，容易产生刷新延时
 static final int xmin = 8;//x轴缩小比例最小值
 static final int ymax = 10;//y轴缩小比例最大值
 static final int ymin = 1;//y轴缩小比例最小值
 
 int recbufsize;//录音最小buffer大小
 audiorecord audiorecord;
 paint mpaint;
  @override
  public void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.main);
    //录音组件
 recbufsize = audiorecord.getminbuffersize(frequency,
  channelconfiguration, audioencoding);
 audiorecord = new audiorecord(mediarecorder.audiosource.mic, frequency,
  channelconfiguration, audioencoding, recbufsize);
 //按键
 btnstart = (button) this.findviewbyid(r.id.btnstart);
 btnstart.setonclicklistener(new clickevent());
 btnexit = (button) this.findviewbyid(r.id.btnexit);
 btnexit.setonclicklistener(new clickevent());
 //画板和画笔
 sfv = (surfaceview) this.findviewbyid(r.id.surfaceview01); 
 sfv.setontouchlistener(new touchevent());
    mpaint = new paint(); 
    mpaint.setcolor(color.green);// 画笔为绿色 
    mpaint.setstrokewidth(1);// 设置画笔粗细 
    //示波器类库
    clsoscilloscope.initoscilloscope(xmax/2, ymax/2, sfv.getheight()/2);
    
    //缩放控件，x轴的数据缩小的比率高些
 zctlx = (zoomcontrols)this.findviewbyid(r.id.zctlx);
 zctlx.setonzoominclicklistener(new view.onclicklistener() {
  @override
  public void onclick(view v) {
  if(clsoscilloscope.ratex>xmin)
   clsoscilloscope.ratex--;
  settitle("x轴缩小"+string.valueof(clsoscilloscope.ratex)+"倍"
   +","+"y轴缩小"+string.valueof(clsoscilloscope.ratey)+"倍");
  }
 });
 zctlx.setonzoomoutclicklistener(new view.onclicklistener() {
  @override
  public void onclick(view v) {
  if(clsoscilloscope.ratex<xmax)
   clsoscilloscope.ratex++; 
  settitle("x轴缩小"+string.valueof(clsoscilloscope.ratex)+"倍"
   +","+"y轴缩小"+string.valueof(clsoscilloscope.ratey)+"倍");
  }
 });
 zctly = (zoomcontrols)this.findviewbyid(r.id.zctly);
 zctly.setonzoominclicklistener(new view.onclicklistener() {
  @override
  public void onclick(view v) {
  if(clsoscilloscope.ratey>ymin)
   clsoscilloscope.ratey--;
  settitle("x轴缩小"+string.valueof(clsoscilloscope.ratex)+"倍"
   +","+"y轴缩小"+string.valueof(clsoscilloscope.ratey)+"倍");
  }
 });
 
 zctly.setonzoomoutclicklistener(new view.onclicklistener() {
  @override
  public void onclick(view v) {
  if(clsoscilloscope.ratey<ymax)
   clsoscilloscope.ratey++; 
  settitle("x轴缩小"+string.valueof(clsoscilloscope.ratex)+"倍"
   +","+"y轴缩小"+string.valueof(clsoscilloscope.ratey)+"倍");
  }
 });
  }
 @override
 protected void ondestroy() {
 super.ondestroy();
 android.os.process.killprocess(android.os.process.mypid());
 }
 
 /**
 * 按键事件处理
 * @author gv
 *
 */
 class clickevent implements view.onclicklistener {
 @override
 public void onclick(view v) {
  if (v == btnstart) {
  clsoscilloscope.baseline=sfv.getheight()/2;
  clsoscilloscope.start(audiorecord,recbufsize,sfv,mpaint);
  } else if (v == btnexit) {
  clsoscilloscope.stop();
  }
 }
 }
 /**
 * 触摸屏动态设置波形图基线
 * @author gv
 *
 */
 class touchevent implements ontouchlistener{
 @override
 public boolean ontouch(view v, motionevent event) {
  clsoscilloscope.baseline=(int)event.gety();
  return true;
 }
 }
}

希望本文实例对于读者进行android项目开发能起到一定的借鉴与帮助作用。