基于Android的计步器(Pedometer)的讲解(四)——后台记步

• 基于Android的计步器(Pedometer)的讲解(四)——后台记步

• 2015-01-07      58 个评论    来源：a296777513的专栏   

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• 今天先不说Pedometer（计步器）项目UI方面的了，今天讲一个基于重力加速度的记步功能传感器（Sensor），然后

  在后台开启记步。

   

  计步器（Pedometer）整个项目的源代码，感兴趣的朋友可以下载来看看(记得帮小弟在github打个星~)

   

  先上几张效果图：（效果和上一篇讲到的CircleBar非常的相似，因为记步功能在后台）

  

  如图所示，能根据你的一些基本参数，来记步。有一个缺点，因为这个是根据感应加速度来计算是否走一步，所以你在原地晃手机，也会记步，不过正常的走路还是挺准确的。

  首先给出StepDetector类的代码：

   

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  package com.example.histogram.widet; 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 ; public static float SENSITIVITY = 10 ; // SENSITIVITY灵敏度 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) { 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) { } }

  
  下来是后台服务StepService的代码：

   

   

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  package com.example.histogram.widet; import android.app.Service; import android.content.Context; import android.content.Intent; import android.hardware.Sensor; import android.hardware.SensorManager; import android.os.IBinder; public class StepService extends Service { public static Boolean flag = false ; private SensorManager sensorManager; private StepDetector stepDetector; @Override public IBinder onBind(Intent arg0) { // TODO Auto-generated method stub return null ; } @Override public void onCreate() { super .onCreate(); //这里开启了一个线程，因为后台服务也是在主线程中进行，这样可以安全点，防止主线程阻塞 new Thread( new Runnable() { public void run() { startStepDetector(); } }).start(); } private void startStepDetector() { flag = true ; stepDetector = new StepDetector( this ); sensorManager = (SensorManager) this .getSystemService(SENSOR_SERVICE); //获取传感器管理器的实例 Sensor sensor = sensorManager .getDefaultSensor(Sensor.TYPE_ACCELEROMETER); //获得传感器的类型，这里获得的类型是加速度传感器 //此方法用来注册，只有注册过才会生效，参数：SensorEventListener的实例，Sensor的实例，更新速率 sensorManager.registerListener(stepDetector, sensor, SensorManager.SENSOR_DELAY_FASTEST); } @Override public int onStartCommand(Intent intent, int flags, int startId) { return super .onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super .onDestroy(); flag = false ; if (stepDetector != null ) { sensorManager.unregisterListener(stepDetector); } } }

  
  最后把FragmentPedometer测试页面的代码也给大家，如果大家看过之前的博客，应该知道这是一个碎片。如果没看过，看兴趣的朋友可以看看之前的博文：

   

   

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  package com.example.histogram; import java.text.SimpleDateFormat; import java.util.Date; import com.example.changepage1.R; import com.example.histogram.widet.CircleBar; import com.example.histogram.widet.StepDetector; import com.example.histogram.widet.StepService; import com.example.histogram.widet.Weather; import android.annotation.SuppressLint; import android.content.Intent; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.view.View.OnClickListener; /** * 这是记步的碎片 * Author: 李垭超 email:[email protected] * Date: 2015-1-6 * Time: 下午8:39 */ public class FragmentPedometer extends Fragment implements OnClickListener{ private View view; private CircleBar circleBar; private int total_step = 0 ; private Thread thread; private int Type = 1 ; private int calories = 0 ; private int step_length = 50 ; private int weight = 70 ; private Weather weather; private String test; private boolean flag = true ; // 来判断第三个页面是否开启动画 @SuppressLint (HandlerLeak) Handler handler = new Handler() { public void handleMessage(Message msg) { super .handleMessage(msg); total_step = StepDetector.CURRENT_SETP; if (Type == 1 ) { circleBar.setProgress(total_step, Type); } else if (Type == 2 ) { calories = ( int ) (weight * total_step * step_length * 0.01 * 0.01 ); circleBar.setProgress(calories, Type); } else if (Type == 3 ) { if (flag) { circleBar.startCustomAnimation(); flag = false ; } if (test != null || weather.getWeather() == null ) { weather.setWeather(正在更新中...); weather.setPtime(); weather.setTemp1(); weather.setTemp2(); circleBar.startCustomAnimation(); circleBar.setWeather(weather); } else { circleBar.setWeather(weather); } } } }; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { view = inflater.inflate(R.layout.pedometer, container, false ); init(); mThread(); return view; } private void init() { Intent intent = new Intent(getActivity(), StepService. class ); getActivity().startService(intent); weather = new Weather(); circleBar = (CircleBar) view.findViewById(R.id.progress_pedometer); circleBar.setMax( 10000 ); circleBar.setProgress(StepDetector.CURRENT_SETP, 1 ); circleBar.startCustomAnimation(); circleBar.setOnClickListener( this ); } private void mThread() { if (thread == null ) { thread = new Thread( new Runnable() { public void run() { while ( true ) { try { Thread.sleep( 500 ); } catch (InterruptedException e) { e.printStackTrace(); } if (StepService.flag) { Message msg = new Message(); handler.sendMessage(msg); } } } }); thread.start(); } } @Override public void onClick(View v) { switch (v.getId()) { case R.id.progress_pedometer: if (Type == 1 ) { Type = 2 ; } else if (Type == 2 ) { flag = true ; Type = 3 ; } else if (Type == 3 ) { Type = 1 ; } Message msg = new Message(); handler.sendMessage(msg); break ; default : break ; } } }