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>  

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;          }                }  }