Android提高之模拟信号示波器的实现

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：

<?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;
}
}
}

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。

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