本文結合SurfaceView實現一個Android版的手機模擬信號示波器(PS：以前也講過J2ME版的手機示波器)。最近物聯網炒得很火，作為手機軟件開發者，如何在不修改手機硬件電路的前提下實現與第三方傳感器結合呢？麥克風就是一個很好的ADC接口，通過麥克風與第三方傳感器結合，再在軟件里對模擬信號做相應的處理，就可以提供更豐富的傳感化應用。
先來看看本文程序運行的效果圖(屏幕錄像速度較慢，真機實際運行起來會更加流暢)：
本文程序使用8000hz的采樣率，對X軸方向繪圖的實時性要求較高，如果不降低X軸的分辨率，程序的實時性較差，因此程序對X軸數據縮小區間為8倍～16倍。由于采用16位采樣，因此Y軸數據的高度相對于手機屏幕來說也偏大，程序也對Y軸數據做縮小，區間為1倍～10倍。在SurfaceView的OnTouchListener方法里加入了波形基線的位置調節，直接在SurfaceView控件上觸摸即可控制整體波形偏上或偏下顯示。
main.xml源碼如下：
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android:layout_height="fill_parent">
android:orientation="horizontal">
android:layout_height="fill_parent">
android:orientation="horizontal">
ClsOscilloscope.java是實現示波器的類庫，包含AudioRecord操作線程和SurfaceView繪圖線程的實現，兩個線程同步操作，代碼如下：
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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
private boolean isRecording = false;// 線程控制標記
/**
* X軸縮小的比例
*/
public int rateX = 4;
/**
* Y軸縮小的比例
*/
public int rateY = 4;
/**
* Y軸基線
*/
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;
}
/**
* 開始
*
* @param recBufSize
* AudioRecord的MinBufferSize
*/
public void Start(AudioRecord audioRecord, int recBufSize, SurfaceView sfv,
Paint mPaint) {
isRecording = true;
new RecordThread(audioRecord, recBufSize).start();// 開始錄制線程
new DrawThread(sfv, mPaint).start();// 開始繪制線程
}
/**
* 停止
*/
public void Stop() {
isRecording = false;
inBuf.clear();// 清除
}
/**
* 負責從MIC保存數據到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();// 開始錄制
while (isRecording) {
// 從MIC保存數據到緩沖區
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);// 添加數據
}
}
audioRecord.stop();
} catch (Throwable t) {
}
}
};
/**
* 負責繪制inBuf中的數據
*
* @author GV
*
*/
class DrawThread extends Thread {
private int oldX = 0;// 上次繪制的X坐標
private int oldY = 0;// 上次繪制的Y坐標
private SurfaceView sfv;// 畫板
private int X_index = 0;// 當前畫圖所在屏幕X軸的坐標
private Paint mPaint;// 畫筆
public DrawThread(SurfaceView sfv, Paint mPaint) {
this.sfv = sfv;
this.mPaint = mPaint;
}
public void run() {
while (isRecording) {
ArrayList
synchronized (inBuf) {
if (inBuf.size() == 0)
continue;
buf = (ArrayList
inBuf.clear();// 清除
}
for (int i = 0; i < buf.size(); i++) {
short[] tmpBuf = buf.get(i);
SimpleDraw(X_index, tmpBuf, rateY, baseLine);// 把緩沖區數據畫出來
X_index = X_index + tmpBuf.length;
if (X_index > sfv.getWidth()) {
X_index = 0;
}
}
}
}
/**
* 繪制指定區域
*
* @param start
* X軸開始的位置(全屏)
* @param buffer
* 緩沖區
* @param rate
* Y軸數據縮小的比例
* @param baseLine
* Y軸基線
*/
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()));// 關鍵:獲取畫布
canvas.drawColor(Color.BLACK);// 清除背景
int y;
for (int i = 0; i < buffer.length; i++) {// 有多少畫多少
int x = i + start;
y = buffer[i] / rate + baseLine;// 調節縮小比例，調節基準線
canvas.drawLine(oldX, oldY, x, y, mPaint);
oldX = x;
oldY = y;
}
sfv.getHolder().unlockCanvasAndPost(canvas);// 解鎖畫布，提交畫好的圖像
}
}
}
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
private boolean isRecording = false;// 線程控制標記
/**
* X軸縮小的比例
*/
public int rateX = 4;
/**
* Y軸縮小的比例
*/
public int rateY = 4;
/**
* Y軸基線
*/
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;
}
/**
* 開始
*
* @param recBufSize
* AudioRecord的MinBufferSize
*/
public void Start(AudioRecord audioRecord, int recBufSize, SurfaceView sfv,
Paint mPaint) {
isRecording = true;
new RecordThread(audioRecord, recBufSize).start();// 開始錄制線程
new DrawThread(sfv, mPaint).start();// 開始繪制線程
}
/**
* 停止
*/
public void Stop() {
isRecording = false;
inBuf.clear();// 清除
}
/**
* 負責從MIC保存數據到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();// 開始錄制
while (isRecording) {
// 從MIC保存數據到緩沖區
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);// 添加數據
}
}
audioRecord.stop();
} catch (Throwable t) {
}
}
};
/**
* 負責繪制inBuf中的數據
*
* @author GV
*
*/
class DrawThread extends Thread {
private int oldX = 0;// 上次繪制的X坐標
private int oldY = 0;// 上次繪制的Y坐標
private SurfaceView sfv;// 畫板
private int X_index = 0;// 當前畫圖所在屏幕X軸的坐標
private Paint mPaint;// 畫筆
public DrawThread(SurfaceView sfv, Paint mPaint) {
this.sfv = sfv;
this.mPaint = mPaint;
}
public void run() {
while (isRecording) {
ArrayList
synchronized (inBuf) {
if (inBuf.size() == 0)
continue;
buf = (ArrayList
inBuf.clear();// 清除
}
for (int i = 0; i < buf.size(); i++) {
short[] tmpBuf = buf.get(i);
SimpleDraw(X_index, tmpBuf, rateY, baseLine);// 把緩沖區數據畫出來
X_index = X_index + tmpBuf.length;
if (X_index > sfv.getWidth()) {
X_index = 0;
}
}
}
}
/**
* 繪制指定區域
*
* @param start
* X軸開始的位置(全屏)
* @param buffer
* 緩沖區
* @param rate
* Y軸數據縮小的比例
* @param baseLine
* Y軸基線
*/
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()));// 關鍵:獲取畫布
canvas.drawColor(Color.BLACK);// 清除背景
int y;
for (int i = 0; i < buffer.length; i++) {// 有多少畫多少
int x = i + start;
y = buffer[i] / rate + baseLine;// 調節縮小比例，調節基準線
canvas.drawLine(oldX, oldY, x, y, mPaint);
oldX = x;
oldY = y;
}
sfv.getHolder().unlockCanvasAndPost(canvas);// 解鎖畫布，提交畫好的圖像
}
}
}
testOscilloscope.java是主程序，控制UI和ClsOscilloscope，代碼如下：
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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軸縮小比例最大值,X軸數據量巨大，容易產生刷新延時
static final int xMin = 8;//X軸縮小比例最小值
static final int yMax = 10;//Y軸縮小比例最大值
static final int yMin = 1;//Y軸縮小比例最小值
int recBufSize;//錄音最小buffer大小
AudioRecord audioRecord;
Paint mPaint;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//錄音組件
recBufSize = AudioRecord.getMinBufferSize(frequency,
channelConfiguration, audioEncoding);
audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, frequency,
channelConfiguration, audioEncoding, recBufSize);
//按鍵
btnStart = (Button) this.findViewById(R.id.btnStart);
btnStart.setOnClickListener(new ClickEvent());
btnExit = (Button) this.findViewById(R.id.btnExit);
btnExit.setOnClickListener(new ClickEvent());
//畫板和畫筆
sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);
sfv.setOnTouchListener(new TouchEvent());
mPaint = new Paint();
mPaint.setColor(Color.GREEN);// 畫筆為綠色
mPaint.setStrokeWidth(1);// 設置畫筆粗細
//示波器類庫
clsOscilloscope.initOscilloscope(xMax/2, yMax/2, sfv.getHeight()/2);
//縮放控件，X軸的數據縮小的比率高些
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軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"
+","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");
}
});
zctlX.setOnZoomOutClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(clsOscilloscope.rateX
setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"
+","+"Y軸縮小"+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軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"
+","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");
}
});
zctlY.setOnZoomOutClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if(clsOscilloscope.rateY
setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"
+","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");
}
});
}
@Override
protected void onDestroy() {
super.onDestroy();
android.os.Process.killProcess(android.os.Process.myPid());
}
/**
* 按鍵事件處理
* @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();
}
}
}
/**
* 觸摸屏動態設置波形圖基線
* @author GV
*
*/
class TouchEvent implements OnTouchListener{
@Override
public boolean onTouch(View v, MotionEvent event) {
clsOscilloscope.baseLine=(int)event.getY();
return true;
}
}
}