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
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
}
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;
}
}
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 !
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