Android提高第十一篇之模拟信号示波器-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_20755/article/details/81991282

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：

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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 >

<?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：

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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
}
}
}

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：

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