Move compass to separate class

mobile/src/com/cradle/iitc_mobile/compass/AccMagCompass.java

@@ -0,0 +1,74 @@
+package com.cradle.iitc_mobile.compass;
+
+import android.content.Context;
+import android.hardware.Sensor;
+import android.hardware.SensorEvent;
+import android.hardware.SensorEventListener;
+import android.hardware.SensorManager;
+
+public class AccMagCompass extends Compass {
+    private static final double SENSOR_DELAY_USER = 100 * 1e6; // 100 milliseconds
+
+    private final Context mContext;
+    private long mLastUpdate = 0;
+    private final SensorListener mListener = new SensorListener();
+    private final float[] mOrientation = new float[3];
+    private final float[] mRotationMatrix = new float[9];
+    private final Sensor mSensorAcc, mSensorMag;
+    private final SensorManager mSensorManager;
+    private float[] mValuesAcc = null, mValuesMag = null;
+
+    public AccMagCompass(final Context context) {
+        mContext = context;
+
+        mSensorManager = (SensorManager) mContext.getSystemService(Context.SENSOR_SERVICE);
+
+        mSensorAcc = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
+        mSensorMag = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
+    }
+
+    private void calculateOrientation() {
+
+        // wait until both sensors have given us an event
+        if (mValuesAcc == null || mValuesMag == null) return;
+
+        if (!SensorManager.getRotationMatrix(mRotationMatrix, null, mValuesAcc, mValuesMag)) return;
+        SensorManager.getOrientation(mRotationMatrix, mOrientation);
+
+        publishOrientation(mOrientation[0], mOrientation[1], mOrientation[2]);
+    }
+
+    @Override
+    protected void onStart() {
+        mSensorManager.registerListener(mListener, mSensorAcc, SensorManager.SENSOR_DELAY_NORMAL);
+        mSensorManager.registerListener(mListener, mSensorMag, SensorManager.SENSOR_DELAY_NORMAL);
+    }
+
+    @Override
+    protected void onStop() {
+        mSensorManager.unregisterListener(mListener);
+    }
+
+    private class SensorListener implements SensorEventListener {
+        @Override
+        public void onAccuracyChanged(final Sensor sensor, final int accuracy) {
+        }
+
+        @Override
+        public void onSensorChanged(final SensorEvent event) {
+            switch (event.sensor.getType()) {
+                case Sensor.TYPE_ACCELEROMETER:
+                    mValuesAcc = event.values;
+                    break;
+                case Sensor.TYPE_MAGNETIC_FIELD:
+                    mValuesMag = event.values;
+
+                    // save some battery, 10 updates per second should be enough
+                    if ((event.timestamp - mLastUpdate) < SENSOR_DELAY_USER) break;
+                    mLastUpdate = event.timestamp;
+
+                    calculateOrientation();
+            }
+        }
+    }
+}

mobile/src/com/cradle/iitc_mobile/compass/Compass.java

@@ -0,0 +1,39 @@
+package com.cradle.iitc_mobile.compass;
+
+import java.util.ArrayList;
+
+public abstract class Compass
+{
+    private final ArrayList<CompassListener> mListeners = new ArrayList<CompassListener>();
+    private boolean mStarted = false;
+
+    protected void publishOrientation(final float x, final float y, final float z)
+    {
+        for (final CompassListener listener : mListeners)
+            listener.onCompassChanged(x, y, z);
+    }
+
+    protected abstract void onStart();
+
+    protected abstract void onStop();
+
+    public void registerListener(final CompassListener listener)
+    {
+        mListeners.add(listener);
+        if (!mStarted)
+        {
+            onStart();
+            mStarted = true;
+        }
+    }
+
+    public void unregisterListener(final CompassListener listener)
+    {
+        mListeners.remove(listener);
+        if (mListeners.size() == 0)
+        {
+            onStop();
+            mStarted = false;
+        }
+    }
+}

mobile/src/com/cradle/iitc_mobile/compass/CompassListener.java

@@ -0,0 +1,5 @@
+package com.cradle.iitc_mobile.compass;
+
+public interface CompassListener {
+    public void onCompassChanged(float x, float y, float z);
+}