Android提高21篇之十一：模擬信號示波器

       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：

1. <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"   
2.         android:orientation="vertical" android:layout_width="fill_parent"  
3.         android:layout_height="fill_parent">  
4.         <linearlayout android:id="@+id/LinearLayout01"   
5.                 android:layout_height="wrap_content" android:layout_width="fill_parent"  
6.                 android:orientation="horizontal">  
7.                 <button android:layout_height="wrap_content" android:id="@+id/btnStart"   
8.                         android:text="開始" android:layout_width="80dip">  
9.                 <button android:layout_height="wrap_content" android:text="停止"   
10.                         android:id="@+id/btnExit" android:layout_width="80dip">  
11.                 <zoomcontrols android:layout_width="wrap_content"   
12.                         android:layout_height="wrap_content" android:id="@+id/zctlX">  
13.                 <zoomcontrols android:layout_width="wrap_content"   
14.                         android:layout_height="wrap_content" android:id="@+id/zctlY">  
15.           
16.         <surfaceview android:id="@+id/SurfaceView01"   
17.                 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：

1. package com.testOscilloscope;  
2. import java.util.ArrayList;  
3. import android.graphics.Canvas;  
4. import android.graphics.Color;  
5. import android.graphics.Paint;  
6. import android.graphics.Rect;  
7. import android.media.AudioRecord;  
8. import android.view.SurfaceView;  
9. public class ClsOscilloscope {  
10.         private ArrayList inBuf = new ArrayList();  
11.         private boolean isRecording = false;// 線程控制標記  
12.         /** 
13.          * X軸縮小的比例 
14.          */  
15.         public int rateX = 4;  
16.         /** 
17.          * Y軸縮小的比例 
18.          */  
19.         public int rateY = 4;  
20.         /** 
21.          * Y軸基線 
22.          */  
23.         public int baseLine = 0;  
24.         /** 
25.          * 初始化 
26.          */  
27.         public void initOscilloscope(int rateX, int rateY, int baseLine) {  
28.                 this.rateX = rateX;  
29.                 this.rateY = rateY;  
30.                 this.baseLine = baseLine;  
31.         }  
32.         /** 
33.          * 開始 
34.          *  
35.          * @param recBufSize 
36.          *            AudioRecord的MinBufferSize 
37.          */  
38.         public void Start(AudioRecord audioRecord, int recBufSize, SurfaceView sfv,  
39.                         Paint mPaint) {  
40.                 isRecording = true;  
41.                 new RecordThread(audioRecord, recBufSize).start();// 開始錄制線程  
42.                 new DrawThread(sfv, mPaint).start();// 開始繪制線程  
43.         }  
44.         /** 
45.          * 停止 
46.          */  
47.         public void Stop() {  
48.                 isRecording = false;  
49.                 inBuf.clear();// 清除  
50.         }  
51.         /** 
52.          * 負責從MIC保存數據到inBuf 
53.          *  
54.          * @author GV 
55.          *  
56.          */  
57.         class RecordThread extends Thread {  
58.                 private int recBufSize;  
59.                 private AudioRecord audioRecord;  
60.                 public RecordThread(AudioRecord audioRecord, int recBufSize) {  
61.                         this.audioRecord = audioRecord;  
62.                         this.recBufSize = recBufSize;  
63.                 }  
64.                 public void run() {  
65.                         try {  
66.                                 short[] buffer = new short[recBufSize];  
67.                                 audioRecord.startRecording();// 開始錄制  
68.                                 while (isRecording) {  
69.                                         // 從MIC保存數據到緩沖區  
70.                                         int bufferReadResult = audioRecord.read(buffer, 0,  
71.                                                         recBufSize);  
72.                                         short[] tmpBuf = new short[bufferReadResult / rateX];  
73.                                         for (int i = 0, ii = 0; i < tmpBuf.length; i++, ii = i  
74.                                                         * rateX) {  
75.                                                 tmpBuf[i] = buffer[ii];  
76.                                         }  
77.                                         synchronized (inBuf) {//  
78.                                                 inBuf.add(tmpBuf);// 添加數據  
79.                                         }  
80.                                 }  
81.                                 audioRecord.stop();  
82.                         } catch (Throwable t) {  
83.                         }  
84.                 }  
85.         };  
86.         /** 
87.          * 負責繪制inBuf中的數據 
88.          *  
89.          * @author GV 
90.          *  
91.          */  
92.         class DrawThread extends Thread {  
93.                 private int oldX = 0;// 上次繪制的X坐標  
94.                 private int oldY = 0;// 上次繪制的Y坐標  
95.                 private SurfaceView sfv;// 畫板  
96.                 private int X_index = 0;// 當前畫圖所在屏幕X軸的坐標  
97.                 private Paint mPaint;// 畫筆  
98.                 public DrawThread(SurfaceView sfv, Paint mPaint) {  
99.                         this.sfv = sfv;  
100.                         this.mPaint = mPaint;  
101.                 }  
102.                 public void run() {  
103.                         while (isRecording) {  
104.                                 ArrayList buf = new ArrayList();  
105.                                 synchronized (inBuf) {  
106.                                         if (inBuf.size() == 0)  
107.                                                 continue;  
108.                                         buf = (ArrayList) inBuf.clone();// 保存  
109.                                         inBuf.clear();// 清除  
110.                                 }  
111.                                 for (int i = 0; i < buf.size(); i++) {  
112.                                         short[] tmpBuf = buf.get(i);  
113.                                         SimpleDraw(X_index, tmpBuf, rateY, baseLine);// 把緩沖區數據畫出來  
114.                                         X_index = X_index + tmpBuf.length;  
115.                                         if (X_index > sfv.getWidth()) {  
116.                                                 X_index = 0;  
117.                                         }  
118.                                 }  
119.                         }  
120.                 }  
121.                 /** 
122.                  * 繪制指定區域 
123.                  *  
124.                  * @param start 
125.                  *            X軸開始的位置(全屏) 
126.                  * @param buffer 
127.                  *            緩沖區 
128.                  * @param rate 
129.                  *            Y軸數據縮小的比例 
130.                  * @param baseLine 
131.                  *            Y軸基線 
132.                  */  
133.                 void SimpleDraw(int start, short[] buffer, int rate, int baseLine) {  
134.                         if (start == 0)  
135.                                 oldX = 0;  
136.                         Canvas canvas = sfv.getHolder().lockCanvas(  
137.                                         new Rect(start, 0, start + buffer.length, sfv.getHeight()));// 關鍵:獲取畫布  
138.                         canvas.drawColor(Color.BLACK);// 清除背景  
139.                         int y;  
140.                         for (int i = 0; i < buffer.length; i++) {// 有多少畫多少  
141.                                 int x = i + start;  
142.                                 y = buffer[i] / rate + baseLine;// 調節縮小比例，調節基准線  
143.                                 canvas.drawLine(oldX, oldY, x, y, mPaint);  
144.                                 oldX = x;  
145.                                 oldY = y;  
146.                         }  
147.                         sfv.getHolder().unlockCanvasAndPost(canvas);// 解鎖畫布，提交畫好的圖像  
148.                 }  
149.         }  
150. }  

       testOscilloscope.java是主程序，控制UI和ClsOscilloscope，代碼如下：

1. package com.testOscilloscope;  
2. import android.app.Activity;  
3. import android.graphics.Color;  
4. import android.graphics.Paint;  
5. import android.media.AudioFormat;  
6. import android.media.AudioRecord;  
7. import android.media.MediaRecorder;  
8. import android.os.Bundle;  
9. import android.view.MotionEvent;  
10. import android.view.SurfaceView;  
11. import android.view.View;  
12. import android.view.View.OnTouchListener;  
13. import android.widget.Button;  
14. import android.widget.ZoomControls;  
15. public class testOscilloscope extends Activity {  
16.     /** Called when the activity is first created. */  
17.         Button btnStart,btnExit;  
18.         SurfaceView sfv;  
19.     ZoomControls zctlX,zctlY;  
20.       
21.     ClsOscilloscope clsOscilloscope=new ClsOscilloscope();  
22.       
23.         static final int frequency = 8000;//分辨率  
24.         static final int channelConfiguration = AudioFormat.CHANNEL_CONFIGURATION_MONO;  
25.         static final int audioEncoding = AudioFormat.ENCODING_PCM_16BIT;  
26.         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  
27.         static final int xMin = 8;//X軸縮小比例最小值  
28.         static final int yMax = 10;//Y軸縮小比例最大值  
29.         static final int yMin = 1;//Y軸縮小比例最小值  
30.           
31.         int recBufSize;//錄音最小buffer大小  
32.         AudioRecord audioRecord;  
33.         Paint mPaint;  
34.     @Override  
35.     public void onCreate(Bundle savedInstanceState) {  
36.         super.onCreate(savedInstanceState);  
37.         setContentView(R.layout.main);  
38.         //錄音組件  
39.                 recBufSize = AudioRecord.getMinBufferSize(frequency,  
40.                                 channelConfiguration, audioEncoding);  
41.                 audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, frequency,  
42.                                 channelConfiguration, audioEncoding, recBufSize);  
43.                 //按鍵  
44.                 btnStart = (Button) this.findViewById(R.id.btnStart);  
45.                 btnStart.setOnClickListener(new ClickEvent());  
46.                 btnExit = (Button) this.findViewById(R.id.btnExit);  
47.                 btnExit.setOnClickListener(new ClickEvent());  
48.                 //畫板和畫筆  
49.                 sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);   
50.                 sfv.setOnTouchListener(new TouchEvent());  
51.         mPaint = new Paint();    
52.         mPaint.setColor(Color.GREEN);// 畫筆為綠色    
53.         mPaint.setStrokeWidth(1);// 設置畫筆粗細   
54.         //示波器類庫  
55.         clsOscilloscope.initOscilloscope(xMax/2, yMax/2, sfv.getHeight()/2);  
56.           
57.         //縮放控件，X軸的數據縮小的比率高些  
58.                 zctlX = (ZoomControls)this.findViewById(R.id.zctlX);  
59.                 zctlX.setOnZoomInClickListener(new View.OnClickListener() {  
60.                         @Override  
61.                         public void onClick(View v) {  
62.                                 if(clsOscilloscope.rateX>xMin)  
63.                                         clsOscilloscope.rateX--;  
64.                                 setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"  
65.                                                 +","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");  
66.                         }  
67.                 });  
68.                 zctlX.setOnZoomOutClickListener(new View.OnClickListener() {  
69.                         @Override  
70.                         public void onClick(View v) {  
71.                                 if(clsOscilloscope.rateX<xmax)  
72.                                         clsOscilloscope.rateX++;          
73.                                 setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"  
74.                                                 +","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");  
75.                         }  
76.                 });  
77.                 zctlY = (ZoomControls)this.findViewById(R.id.zctlY);  
78.                 zctlY.setOnZoomInClickListener(new View.OnClickListener() {  
79.                         @Override  
80.                         public void onClick(View v) {  
81.                                 if(clsOscilloscope.rateY>yMin)  
82.                                         clsOscilloscope.rateY--;  
83.                                 setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"  
84.                                                 +","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");  
85.                         }  
86.                 });  
87.                   
88.                 zctlY.setOnZoomOutClickListener(new View.OnClickListener() {  
89.                         @Override  
90.                         public void onClick(View v) {  
91.                                 if(clsOscilloscope.rateY<ymax)  
92.                                         clsOscilloscope.rateY++;          
93.                                 setTitle("X軸縮小"+String.valueOf(clsOscilloscope.rateX)+"倍"  
94.                                                 +","+"Y軸縮小"+String.valueOf(clsOscilloscope.rateY)+"倍");  
95.                         }  
96.                 });  
97.     }  
98.         @Override  
99.         protected void onDestroy() {  
100.                 super.onDestroy();  
101.                 android.os.Process.killProcess(android.os.Process.myPid());  
102.         }  
103.           
104.         /** 
105.          * 按鍵事件處理 
106.          * @author GV 
107.          * 
108.          */  
109.         class ClickEvent implements View.OnClickListener {  
110.                 @Override  
111.                 public void onClick(View v) {  
112.                         if (v == btnStart) {  
113.                                 clsOscilloscope.baseLine=sfv.getHeight()/2;  
114.                                 clsOscilloscope.Start(audioRecord,recBufSize,sfv,mPaint);  
115.                         } else if (v == btnExit) {  
116.                                 clsOscilloscope.Stop();  
117.                         }  
118.                 }  
119.         }  
120.         /** 
121.          * 觸摸屏動態設置波形圖基線 
122.          * @author GV 
123.          * 
124.          */  
125.         class TouchEvent implements OnTouchListener{  
126.                 @Override  
127.                 public boolean onTouch(View v, MotionEvent event) {  
128.                         clsOscilloscope.baseLine=(int)event.getY();  
129.                         return true;  
130.                 }  
131.                   
132.         }  
133. }