Android提高之模擬信號示波器的實現

前面簡單地介紹了Android程序開發中AudioRecord和AudioTrack的使用，這次再結合SurfaceView實現一個Android版的手機模擬信號示波器。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，再在軟件裡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(屏幕錄像截圖的速度較慢，真機實際運行起來會很流暢)：

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。由於采用16位采樣，因此Y軸數據的高度相對於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方法裡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：

<?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="開始" 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：

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;// 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<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，調節基准線
  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：

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<xMax)
   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<yMax)
   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;
 }
 }
}

希望本文實例對於讀者進行Android項目開發能起到一定的借鑒與幫助作用。