Android 模拟信号示波器示例代码

       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：

XML/HTML代码

         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 inBuf = new ArrayList(); 
    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 buf = new ArrayList(); 
                synchronized (inBuf) { 
                    if (inBuf.size() == 0) 
                        continue; 
                    buf = (ArrayList) 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.rateXyMin) 
                    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 
 

         以上就是对Android 实现模拟系信号示波器的示例详解，后续继续补充相关知识，谢谢大家对本站 的支持！