11.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。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：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

<? 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_width = "fill_parent" android:layout_height = "wrap_content" android:orientation = "horizontal" > < Button android:id = "@+id/btnStart" android:layout_width = "80dip" android:layout_height = "wrap_content" android:text = "开始" /> < Button android:id = "@+id/btnExit" android:layout_width = "80dip" android:layout_height = "wrap_content" android:text = "停止" /> < ZoomControls android:id = "@+id/zctlX" android:layout_width = "wrap_content" android:layout_height = "wrap_content" /> < ZoomControls android:id = "@+id/zctlY" android:layout_width = "wrap_content" android:layout_height = "wrap_content" /> </ 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：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162

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 public int rateX =  4 ; public int rateY =  4 ; public int baseLine =  ; public void initOscilloscope( int rateX,  int rateY,  int baseLine) { this .rateX = rateX; this .rateY = rateY; this .baseLine = baseLine; } 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 } public void Stop() { isRecording =  false ; inBuf.clear(); // 清除 } 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,  , recBufSize); short [] tmpBuf =  new short [bufferReadResult / rateX]; for ( int i =  , ii =  ; 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) { } } }; class DrawThread  extends Thread { private int oldX =  ; // 上次绘制的X坐标 private int oldY =  ; // 上次绘制的Y坐标 private SurfaceView sfv; // 画板 private int X_index =  ; // 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() ==  ) continue ; buf = (ArrayList< short []>) inBuf.clone(); // 保存 inBuf.clear(); // 清除 } for ( int i =  ; 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 =  ; } } } } void SimpleDraw( int start,  short [] buffer,  int rate,  int baseLine) { if (start ==  ) oldX =  ; Canvas canvas = sfv.getHolder().lockCanvas( new Rect(start,  , start + buffer.length, sfv.getHeight())); // 关键:获取画布 canvas.drawColor(Color.BLACK); // 清除背景 int y; for ( int i =  ; 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：

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145

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 { 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()); } 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(); } } } class TouchEvent  implements OnTouchListener { @Override public boolean onTouch(View v, MotionEvent event) { clsOscilloscope.baseLine = ( int ) event.getY(); return true ; } } }