package com.altria.mystep.step;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
/**
* 这是一个实现了信号监听的记步的类
* 这是从谷歌找来的一个记步的算法，看不太懂
* @author Liyachao Date:2015-1-6
*
*/
public class StepDetector implements SensorEventListener {
public static int CURRENT_SETP = 0;//当前步数
public static float SENSITIVITY = 10; // SENSITIVITY灵敏度
public static boolean flag = false;//服务运行标志
private float mLastValues[] = new float[3 * 2];
private float mScale[] = new float[2];
private float mYOffset;
private static long end = 0;
private static long start = 0;
/**
* 最后加速度方向
*/
private float mLastDirections[] = new float[3 * 2];
private float mLastExtremes[][] = { new float[3 * 2], new float[3 * 2] };
private float mLastDiff[] = new float[3 * 2];
private int mLastMatch = -1;
/**
* 传入上下文的构造函数
*
* @param context
*/
public StepDetector(Context context) {
super();
int h = 480;
mYOffset = h * 0.5f;
mScale[0] = -(h * 0.5f * (1.0f / (SensorManager.STANDARD_GRAVITY * 2)));
mScale[1] = -(h * 0.5f * (1.0f / (SensorManager.MAGNETIC_FIELD_EARTH_MAX)));
}
//当加速度传感器检测到的数值发生变化时就会调用这个方法
public void onSensorChanged(SensorEvent event) {
if (!flag)
return;
Sensor sensor = event.sensor;
synchronized (this) {
if (sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
float vSum = 0;
for (int i = 0; i < 3; i++) {
final float v = mYOffset + event.values[i] * mScale[1];
vSum += v;
}
int k = 0;
float v = vSum / 3;
float direction = (v > mLastValues[k] ? 1
: (v < mLastValues[k] ? -1 : 0));
if (direction == -mLastDirections[k]) {
// Direction changed
int extType = (direction > 0 ? 0 : 1); // minumum or
// maximum?
mLastExtremes[extType][k] = mLastValues[k];
float diff = Math.abs(mLastExtremes[extType][k]
- mLastExtremes[1 - extType][k]);
if (diff > SENSITIVITY) {
boolean isAlmostAsLargeAsPrevious = diff > (mLastDiff[k] * 2 / 3);
boolean isPreviousLargeEnough = mLastDiff[k] > (diff / 3);
boolean isNotContra = (mLastMatch != 1 - extType);
if (isAlmostAsLargeAsPrevious && isPreviousLargeEnough
&& isNotContra) {
end = System.currentTimeMillis();
if (end - start > 500) {// 此时判断为走了一步
CURRENT_SETP++;
mLastMatch = extType;
start = end;
}
} else {
mLastMatch = -1;
}
}
mLastDiff[k] = diff;
}
mLastDirections[k] = direction;
mLastValues[k] = v;
}
}
}
//当传感器的经度发生变化时就会调用这个方法，在这里没有用
public void onAccuracyChanged(Sensor arg0, int arg1) {
}
}
为梦想努力_冬