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:296777513@qq.com   * 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 ;          }                }   }

原文：http://my.oschina.net/u/1049180/blog/471473