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

<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 android:layout_height="wrap_content" android:text="停止"
            android:id="@+id/btnExit" android:layout_width="80dip">
        <zoomcontrols android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/zctlX">
        <zoomcontrols android:layout_width="wrap_content"
            android:layout_height="wrap_content" android:id="@+id/zctlY"> 

    <surfaceview android:id="@+id/SurfaceView01"
        android:layout_height="fill_parent" android:layout_width="fill_parent"> 

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.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;
        } 

    }
} 

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！