Android 模擬信號示波器示例代碼

       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：

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; 
        } 
         
    } 
} 

         以上就是對Android 實現模擬系信號示波器的示例詳解，後續繼續補充相關知識，謝謝大家對本站 的支持！