上次簡單地介紹了AudioRecord和AudioTrack的使用，這次就結合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：
XML/HTML代碼
<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 android:layout_height="wrap_content" android:text="停止" android:id="@+id/btnExit" android:layout_width="80dip"> <zoomcontrols android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/zctlX"> <zoomcontrols android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/zctlY"> <surfaceview android:id="@+id/SurfaceView01" android:layout_height="fill_parent" android:layout_width="fill_parent">
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 inBuf = new 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 buf = new ArrayList(); synchronized (inBuf) { if (inBuf.size() == 0) continue; buf = (ArrayList) 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：
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; } } } 以上就是對Android 實現模擬系信號示波器的示例詳解，后續繼續補充相關知識，謝謝大家對本站 的支持！
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