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。