Android使用Sensor感应器获取用户移动方向(指南针原理)

/* 
 * @author octobershiner 
 * 2011 07 28 
 * SE.HIT 
 * 一个演示通过磁场和加速度两个感应器获取方向数据的例子 
 * */ 
package uni.sensor; 
import android.app.Activity; 
import android.content.Context; 
import android.hardware.Sensor; 
import android.hardware.SensorEvent; 
import android.hardware.SensorEventListener; 
import android.hardware.SensorManager; 
import android.os.Bundle; 
import android.util.Log; 
public class OrientationActivity extends Activity{ 
 private SensorManager sm; 
 //需要两个Sensor 
 private Sensor aSensor; 
 private Sensor mSensor; 
 float[] accelerometerValues = new float[3]; 
 float[] magneticFieldValues = new float[3]; 
 private static final String TAG = "sensor"; 
 @Override 
 public void onCreate(Bundle savedInstanceState) { 
  // TODO Auto-generated method stub 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.main); 
  sm = (SensorManager)getSystemService(Context.SENSOR_SERVICE); 
  aSensor = sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER); 
  mSensor = sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD); 
  sm.registerListener(myListener, aSensor, SensorManager.SENSOR_DELAY_NORMAL); 
  sm.registerListener(myListener, mSensor,SensorManager.SENSOR_DELAY_NORMAL); 
  //更新显示数据的方法 
  calculateOrientation(); 
 } 
 //再次强调：注意activity暂停的时候释放 
 public void onPause(){ 
  sm.unregisterListener(myListener); 
  super.onPause(); 
 }  
 final SensorEventListener myListener = new SensorEventListener() { 
 public void onSensorChanged(SensorEvent sensorEvent) { 
 if (sensorEvent.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) 
 magneticFieldValues = sensorEvent.values; 
 if (sensorEvent.sensor.getType() == Sensor.TYPE_ACCELEROMETER) 
  accelerometerValues = sensorEvent.values; 
 calculateOrientation(); 
 } 
 public void onAccuracyChanged(Sensor sensor, int accuracy) {} 
 }; 
 private void calculateOrientation() { 
   float[] values = new float[3]; 
   float[] R = new float[9]; 
   SensorManager.getRotationMatrix(R, null, accelerometerValues, magneticFieldValues);   
   SensorManager.getOrientation(R, values); 
   // 要经过一次数据格式的转换，转换为度 
   values[0] = (float) Math.toDegrees(values[0]); 
   Log.i(TAG, values[0]+""); 
   //values[1] = (float) Math.toDegrees(values[1]); 
   //values[2] = (float) Math.toDegrees(values[2]); 
   if(values[0] >= -5 && values[0] <5){ 
    Log.i(TAG, "正北"); 
   } 
   else if(values[0] >= 5 && values[0] <85){ 
    Log.i(TAG, "东北"); 
   } 
   else if(values[0] >= 85 && values[0] <=95){ 
    Log.i(TAG, "正东"); 
   } 
   else if(values[0] >= 95 && values[0] <175){ 
    Log.i(TAG, "东南"); 
   } 
   else if((values[0] >= 175 && values[0] <= 180) || (values[0]) >= -180 && values[0] <-175){ 
    Log.i(TAG, "正南"); 
   } 
   else if(values[0] >= -175 && values[0] <-95){ 
    Log.i(TAG, "西南"); 
   } 
   else if(values[0] >= -95 && values[0] <-85){ 
    Log.i(TAG, "正西"); 
   } 
   else if(values[0] >= -85 && values[0] <-5){ 
    Log.i(TAG, "西北"); 
   } 
  }
}