Android提高第十一篇之模拟信号示波器

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

       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() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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");}}); }@Overrideprotected 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 {@Overridepublic 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{@Overridepublic boolean onTouch(View v, MotionEvent event) {clsOscilloscope.baseLine=(int)event.getY();return true;}}}