Orientation Listener Hlidskialf Codes

A listener class for detecting orientation changes.

/* The following code was written by 
 * 
 *   Matthew Wiggins (Jun 2009)
 *
 * and is released under the APACHE 2.0 license
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 */
package com.hlidskialf.android.hardware;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import java.lang.UnsupportedOperationException;
import java.util.List;

public class OrientationListener implements SensorEventListener 
{
  public static final int ORIENTATION_UNDETERMINED=-1;
  public static final int ORIENTATION_NORTH=0;
  public static final int ORIENTATION_EAST=1;
  public static final int ORIENTATION_SOUTH=2;
  public static final int ORIENTATION_WEST=3;

  private SensorManager mSensorMgr;
  private Sensor mSensor;
  private Context mContext;
  private int mCurOrientation = ORIENTATION_UNDETERMINED;
  private OnRotateListener mRotateListener;

  public interface OnRotateListener
  {
    public void onRotate(int orientation);
  }


  public OrientationListener(Context context)
  {
    mContext = context;
  }

  public void resume() {
    mSensorMgr = (SensorManager)mContext.getSystemService(Context.SENSOR_SERVICE);
    if (mSensorMgr == null) {
      throw new UnsupportedOperationException("Sensors not supported");
    }

    List sensors = mSensorMgr.getSensorList(Sensor.TYPE_ORIENTATION);
    if (sensors.size() < 1) 
      throw new UnsupportedOperationException("Orientation not supported");
    mSensor = sensors.get(0);
    if (!mSensorMgr.registerListener(this, mSensor, SensorManager.SENSOR_DELAY_UI)) 
      throw new UnsupportedOperationException("Orientation not supported");
  }
  public void pause() {
    if (mSensorMgr != null) {
      mSensorMgr.unregisterListener(this, mSensor);
      mSensorMgr = null;
    }
  }
  public void onAccuracyChanged(Sensor sensor, int accuracy) {}
  public void onSensorChanged(SensorEvent event)
  {
    int new_orient = which_orientation(event.values[0]);
    if (new_orient == ORIENTATION_UNDETERMINED) 
      return;

    if (new_orient != mCurOrientation) {
      mCurOrientation = new_orient;
      if (mRotateListener != null) {
        mRotateListener.onRotate(new_orient);
      }
    }
  }

  private int which_orientation(float angle)
  {
    if ((angle < 90) && (angle > 0))
      return ORIENTATION_NORTH;
    if ((angle < 180) && (angle > 90))
      return ORIENTATION_EAST;
    if ((angle < 270) && (angle > 180))
      return ORIENTATION_SOUTH;
    if ((angle < 360) && (angle > 270))
      return ORIENTATION_WEST;
    return ORIENTATION_UNDETERMINED;
  }

  public void setOnRotateListener(OnRotateListener lstnr)
  {
    mRotateListener = lstnr;
  }
}