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;  
        }  
          
    }  
}