前面简单地介绍了android程序开发中audiorecord和audiotrack的使用，这次再结合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(屏幕录像截图的速度较慢，真机实际运行起来会很流畅)：
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：
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<?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>
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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：
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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
}
}
}
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testoscilloscope.java是主程序，控制ui和clsoscilloscope，代码如下：
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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;
}
}
}
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希望本文实例对于读者进行android项目开发能起到一定的借鉴与帮助作用。