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！