Android Open Source - Android-Sessions Compass Activity

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License

The source code is released under:
MIT License
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Java Source Code

package uk.ac.icappsoc.appsocthree.compass;
/*from  w w  w  .j a  va  2 s .c o  m*/
import uk.ac.icappsoc.appsocthree.R;
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;

public class CompassActivity extends Activity implements SensorEventListener {

  /**
   *  A reference to the system SensorManager, which we use to access all the sensors we'll want.
   *  In our case, we'll use it to start and stop listening for sensor events, as well as retrieve
   *  references to the sensors we will use.
   */
  private SensorManager sensorManager;
  
  private CompassView compass;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_compass);
    
    // Retrieve the SensorManager and get a reference to the sensor we want.
    sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);

    // Grab our CompassView so we can update it with the latest orientation!
    compass = (CompassView) findViewById(R.id.compass);
  }

  // Note that onResume() is called every time an Activity comes to the foreground, including the first time it starts up.
  @Override
  protected void onResume(){
    super.onResume();
    // Register this Activity as the listener for our gravity and magnetic sensor as soon as we resume running.
    sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_GRAVITY), SensorManager.SENSOR_DELAY_UI);
    // Register for ACCELEROMETER as well as GRAVITY sensor, in case GRAVITY sensor is not present.
    sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_UI);
    sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD), SensorManager.SENSOR_DELAY_UI);
  }

  @Override
  protected void onPause(){
    super.onPause();
    // Unregister this Activity as soon as it's paused to prevent battery drain.
    sensorManager.unregisterListener(this);
  }

  @Override
  public void onAccuracyChanged(Sensor sensor, int accuracy) {
    // Typically we're not too interested in doing anything here.
  }

  
  // 1 radian = 57.2957795 degrees
  private static final float DEGREES_PER_RADIAN = 57.2957795f;
  
  // All the necessary arrays to store and compute orientation values.
  private float[] rotationMatrix = new float[9];
  private float[] orientation = new float[3];
  private float[] latestAccelerations = new float[3];
  private float[] latestMagFields = new float[3];

  private boolean haveAccData = false;
  private boolean haveGravData = false;
  private boolean haveMagData = false;
  
  @Override
  public void onSensorChanged(SensorEvent event) {
    // Here's where the meat lies!
    switch(event.sensor.getType()){
    case Sensor.TYPE_GRAVITY:
      System.arraycopy(event.values, 0, latestAccelerations, 0, 3);
      haveGravData = true;
      break;
    case Sensor.TYPE_ACCELEROMETER:
      if(haveGravData) break; // GRAVITY sensor data is better!
      System.arraycopy(event.values, 0, latestAccelerations, 0, 3);
      haveAccData = true;
      break;
    case Sensor.TYPE_MAGNETIC_FIELD:
      System.arraycopy(event.values, 0, latestMagFields, 0, 3);
      haveMagData = true;
      break;
    }
    
    if((haveGravData || haveAccData) && haveMagData){
      // We've got all the data we need to calculate orientation relative to magnetic north!
      if(SensorManager.getRotationMatrix(rotationMatrix, null, latestAccelerations, latestMagFields)){
        SensorManager.getOrientation(rotationMatrix, orientation);
        
        /* orientation[0] : azimuth, rotation around Z axis
         * orientation[1] : pitch, rotation around X axis
         * orientation[2] : roll, rotation around Y axis */
        float azimuth = orientation[0] * DEGREES_PER_RADIAN;
        
        // Update our compass!
        compass.setAzimuthDampedSmart(azimuth, 0.05f);
      }
    }
  }

}
Java Source Code List
