Android提高第十一篇之模拟信号示波器

上次简单地介绍了 AudioRecord和AudioTrack的使用 ，这次就结合SurfaceView 实现一个Android版的手机模拟信号示波器(PS：以前也讲过J2ME版的手机示波器 )。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(屏幕录像速度较慢，真机实际运行起来会更加流畅)：

       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 >

<?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
         }
     }
 }

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 ;
         }

     }
 }