content: /*
   * Copyright (C) 2008 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.view;
  
  import android.content.Context;
  import android.hardware.Sensor;
  import android.hardware.SensorEvent;
  import android.hardware.SensorEventListener;
  import android.hardware.SensorManager;
  import android.util.Log;
  
  /**
   * Helper class for receiving notifications from the SensorManager when
   * the orientation of the device has changed.
   */
  public abstract class OrientationEventListener {
      private static final String TAG = "OrientationEventListener";
      private static final boolean DEBUG = false;
      private static final boolean localLOGV = false;
      private int mOrientation = ORIENTATION_UNKNOWN;
      private SensorManager mSensorManager;
      private boolean mEnabled = false;
      private int mRate;
      private Sensor mSensor;
      private SensorEventListener mSensorEventListener;
      private OrientationListener mOldListener;
      
      /**
       * Returned from onOrientationChanged when the device orientation cannot be determined
       * (typically when the device is in a close to flat position).
       *
       *  @see #onOrientationChanged
       */
      public static final int ORIENTATION_UNKNOWN = -1;
  
      /**
       * Creates a new OrientationEventListener.
       * 
       * @param context for the OrientationEventListener.
       */
      public OrientationEventListener(Context context) {
          this(context, SensorManager.SENSOR_DELAY_NORMAL);
      }
      
      /**
       * Creates a new OrientationEventListener.
       * 
       * @param context for the OrientationEventListener.
       * @param rate at which sensor events are processed (see also
       * {@link android.hardware.SensorManager SensorManager}). Use the default
       * value of {@link android.hardware.SensorManager#SENSOR_DELAY_NORMAL 
       * SENSOR_DELAY_NORMAL} for simple screen orientation change detection.
       */
      public OrientationEventListener(Context context, int rate) {
          mSensorManager = (SensorManager)context.getSystemService(Context.SENSOR_SERVICE);
          mRate = rate;
          mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
          if (mSensor != null) {
              // Create listener only if sensors do exist
              mSensorEventListener = new SensorEventListenerImpl();
          }
      }
      
      void registerListener(OrientationListener lis) {
          mOldListener = lis;
      }
  
      /**
       * Enables the OrientationEventListener so it will monitor the sensor and call
       * {@link #onOrientationChanged} when the device orientation changes.
       */
      public void enable() {
          if (mSensor == null) {
              Log.w(TAG, "Cannot detect sensors. Not enabled");
              return;
          }
          if (mEnabled == false) {
              if (localLOGV) Log.d(TAG, "OrientationEventListener enabled");
              mSensorManager.registerListener(mSensorEventListener, mSensor, mRate);
              mEnabled = true;
          }
      }
  
      /**
       * Disables the OrientationEventListener.
       */
      public void disable() {
          if (mSensor == null) {
              Log.w(TAG, "Cannot detect sensors. Invalid disable");
              return;
          }
          if (mEnabled == true) {
              if (localLOGV) Log.d(TAG, "OrientationEventListener disabled");
              mSensorManager.unregisterListener(mSensorEventListener);
              mEnabled = false;
          }
      }
  
      class SensorEventListenerImpl implements SensorEventListener {
          private static final int _DATA_X = 0;
          private static final int _DATA_Y = 1;
          private static final int _DATA_Z = 2;
          
          public void onSensorChanged(SensorEvent event) {
              float[] values = event.values;
              int orientation = ORIENTATION_UNKNOWN;
              float X = -values[_DATA_X];
              float Y = -values[_DATA_Y];
              float Z = -values[_DATA_Z];        
              float magnitude = X*X + Y*Y;
              // Don't trust the angle if the magnitude is small compared to the y value
              if (magnitude * 4 >= Z*Z) {
                  float OneEightyOverPi = 57.29577957855f;
                  float angle = (float)Math.atan2(-Y, X) * OneEightyOverPi;
                  orientation = 90 - (int)Math.round(angle);
                  // normalize to 0 - 359 range
                  while (orientation >= 360) {
                      orientation -= 360;
                  } 
                  while (orientation < 0) {
                      orientation += 360;
                  }
              }
              if (mOldListener != null) {
                  mOldListener.onSensorChanged(Sensor.TYPE_ACCELEROMETER, event.values);
              }
              if (orientation != mOrientation) {
                  mOrientation = orientation;
                  onOrientationChanged(orientation);
              }
          }
  
          public void onAccuracyChanged(Sensor sensor, int accuracy) {
  
          }
      }
      
      /*
       * Returns true if sensor is enabled and false otherwise
       */
      public boolean canDetectOrientation() {
          return mSensor != null;
      }
  
      /**
       * Called when the orientation of the device has changed.
       * orientation parameter is in degrees, ranging from 0 to 359.
       * orientation is 0 degrees when the device is oriented in its natural position,
       * 90 degrees when its left side is at the top, 180 degrees when it is upside down, 
       * and 270 degrees when its right side is to the top.
       * {@link #ORIENTATION_UNKNOWN} is returned when the device is close to flat
       * and the orientation cannot be determined.
       *
       * @param orientation The new orientation of the device.
       *
       *  @see #ORIENTATION_UNKNOWN
       */
      abstract public void onOrientationChanged(int orientation);
  }
  