开源一个款好看的分贝仪

SoundMeter(分贝仪)

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详细介绍

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android端的声音检测程序，实时获取当前周围环境的声压级，也就是平常所说的分贝值

源码

声音采集利用系统的MediaRecorder

/**  * 录音  * @return 是否成功开始录音  */ public boolean startRecorder(){     if (myRecAudioFile == null) {         return false;     }     try {         mMediaRecorder = new MediaRecorder();          mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);         mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);         mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);         mMediaRecorder.setOutputFile(myRecAudioFile.getAbsolutePath());          mMediaRecorder.prepare();         mMediaRecorder.start();         isRecording = true;         return true;     } catch(IOException exception) {         mMediaRecorder.reset();         mMediaRecorder.release();         mMediaRecorder = null;         isRecording = false ;         exception.printStackTrace();     }catch(IllegalStateException e){         stopRecording();         e.printStackTrace();         isRecording = false ;     }     return false; }   /**   * 获取声压值   */  public float getMaxAmplitude() {      if (mMediaRecorder != null) {          try {              return mMediaRecorder.getMaxAmplitude();          } catch (IllegalArgumentException e) {              e.printStackTrace();              return 0;          }      } else {          return 5;      }  } 

自定义显示分贝值得大圆盘View 取名SoundDiscView

private float scaleWidth, scaleHeight; private int newWidth, newHeight; private Matrix mMatrix = new Matrix(); private Bitmap indicatorBitmap; private Paint paint = new Paint(); static final long  ANIMATION_INTERVAL = 100;   private void init() {     Bitmap myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.noise_index);     int bitmapWidth = myBitmap.getWidth();     int bitmapHeight = myBitmap.getHeight();     newWidth = getWidth();     newHeight = getHeight();     scaleWidth = ((float) newWidth) /(float) bitmapWidth;  // 获取缩放比例     scaleHeight = ((float) newHeight) /(float) bitmapHeight;  //获取缩放比例     mMatrix.postScale(scaleWidth, scaleHeight);   //设置mMatrix的缩放比例     indicatorBitmap = Bitmap.createBitmap(myBitmap, 0, 0, bitmapWidth, bitmapHeight, mMatrix,true);  //获取同等和背景宽高的指针图的bitmap      paint = new Paint();     paint.setTextSize(55);     paint.setAntiAlias(true);     paint.setTextAlign(Paint.Align.CENTER);  //抗锯齿     paint.setColor(Color.WHITE); }   @Override protected void onDraw(Canvas canvas) {     super.onDraw(canvas);     currentAngle = getAngle(World.dbCount); //获取指针应该显示的角度     mMatrix.setRotate(getAngle(World.dbCount), newWidth / 2, newHeight * 215 / 460);   //片相对位置     canvas.drawBitmap(indicatorBitmap, mMatrix, paint);     postInvalidateDelayed(ANIMATION_INTERVAL);     canvas.drawText((int)World.dbCount+" DB", newWidth/2,newHeight*36/46, paint); //图片相对位置 } 

启动、暂停与关闭

控制的所有操作全部在MainActivity里进行的，当启动或者重新进入activity时启动分贝仪，启动代码如下：

 @Override protected void onResume() {     super.onResume();     bListener = true;     File file = FileUtil.createFile("temp.amr"); //创建录音文件     if (file != null) {         Log.v("file", "file =" + file.getAbsolutePath());         startRecord(file);     } else {         Toast.makeText(getApplicationContext(), "创建文件失败", Toast.LENGTH_LONG).show();     } }  /**  * 开始记录  * @param fFile  */ public void startRecord(File fFile){     try{         mRecorder.setMyRecAudioFile(fFile);         if (mRecorder.startRecorder()) {             startListenAudio();         }else{             Toast.makeText(this, "启动录音失败", Toast.LENGTH_SHORT).show();         }     }catch(Exception e){         Toast.makeText(this, "录音机已被占用", Toast.LENGTH_SHORT).show();         e.printStackTrace();     } }    private void startListenAudio() {     thread = new Thread(new Runnable() {         @Override         public void run() {             while (isThreadRun) {                 try {                     if(bListener) {                         volume = mRecorder.getMaxAmplitude();  //获取声压值                         if(volume > 0 && volume < 1000000) {                             World.setDbCount(20 * (float)(Math.log10(volume)));  //将声压值转为分贝值                             soundDiscView.refresh(); //子线程刷新view，调用了postInvalidate                         }                     }                     Thread.sleep(100);                 } catch (InterruptedException e) {                     e.printStackTrace();                     bListener = false;                 }             }         }     });     thread.start(); } 

startListenAudio的执行过程就是开启一个线程，每隔一段时间获取分贝值然后刷新大圆盘，这里要注意的是在子线程操作刷新view的时候要用postInvalidate，查看postInvalidate的源码发现其原理很简单，它就是v用了一个handler机制，最终刷新肯定是在主线程的。

当activity被onStop时我们要停止与关闭录音采集，然后删除采集的文件，操作如下：

/**  * 停止记录  */ @Override protected void onStop() {     super.onStop();     bListener = false;     mRecorder.delete(); //停止记录并删除录音文件 }   public void delete() {         stopRecording();         if (myRecAudioFile != null) {             myRecAudioFile.delete();             myRecAudioFile = null;         }    } 

执行

整个效果还行，但是运行发现指针滑动的太突兀，做个缓慢过度

public static float dbCount = 40;  private static float lastDbCount = dbCount; private static float min = 0.5f; private static float value = 0; public static void setDbCount(float dbValue) {     if (dbValue > lastDbCount) {         value = dbValue - lastDbCount > min ? dbValue - lastDbCount : min;     }else{         value = dbValue - lastDbCount < -min ? dbValue - lastDbCount : -min;     }     dbCount = lastDbCount + value * 0.2f ;     lastDbCount = dbCount; } 

再次执行，perfect !