Merge "Improve accelerometer-based orientation sensing."

     * {@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.

     *

     * This constructor is private since no one uses it and making it public would complicate

     * things, since the lowpass filtering code depends on the actual sampling period, and there's

     * no way to get the period from SensorManager based on the rate constant.

     */

    public WindowOrientationListener(Context context, int rate) {

    private WindowOrientationListener(Context context, int rate) {

        mSensorManager = (SensorManager)context.getSystemService(Context.SENSOR_SERVICE);

        mRate = rate;

        mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

    }

    class SensorEventListenerImpl implements SensorEventListener {

        // We work with all angles in degrees in this class.

        private static final float RADIANS_TO_DEGREES = (float) (180 / Math.PI);

        // Indices into SensorEvent.values

        private static final int _DATA_X = 0;

        private static final int _DATA_Y = 1;

        private static final int _DATA_Z = 2;

        // Angle around x-asis that's considered almost too vertical. Beyond

        // this angle will not result in any orientation changes. f phone faces uses,

        // the device is leaning backward.

        private static final int PIVOT_UPPER = 65;

        // Angle about x-axis that's considered negative vertical. Beyond this

        // angle will not result in any orientation changes. If phone faces uses,

        // the device is leaning forward.

        private static final int PIVOT_LOWER = -10;

        static final int ROTATION_0 = 0;

        static final int ROTATION_90 = 1;

        static final int ROTATION_180 = 2;

        static final int ROTATION_270 = 3;

        int mRotation = ROTATION_0;

        // Threshold values defined for device rotation positions

        // follow order ROTATION_0 .. ROTATION_270

        final int THRESHOLDS[][][] = new int[][][] {

            {{60, 135}, {135, 225}, {225, 300}},

                {{0, 45}, {45, 135}, {135, 210}, {330, 360}},

                {{0, 45}, {45, 120}, {240, 315}, {315, 360}},

                {{0, 30}, {150, 225}, {225, 315}, {315, 360}}

        // Internal aliases for the four orientation states.  ROTATION_0 = default portrait mode,

        // ROTATION_90 = left side of device facing the sky, etc.

        private static final int ROTATION_0 = 0;

        private static final int ROTATION_90 = 1;

        private static final int ROTATION_180 = 2;

        private static final int ROTATION_270 = 3;

        // Current orientation state

        private int mRotation = ROTATION_0;

        // Mapping our internal aliases into actual Surface rotation values

        private final int[] SURFACE_ROTATIONS = new int[] {Surface.ROTATION_0, Surface.ROTATION_90,

                Surface.ROTATION_180, Surface.ROTATION_270};

        // Threshold ranges of orientation angle to transition into other orientation states.

        // The first list is for transitions from ROTATION_0, the next for ROTATION_90, etc.

        // ROTATE_TO defines the orientation each threshold range transitions to, and must be kept

        // in sync with this.

        // The thresholds are nearly regular -- we generally transition about the halfway point

        // between two states with a swing of 30 degreees for hysteresis.  For ROTATION_180,

        // however, we enforce stricter thresholds, pushing the thresholds 15 degrees closer to 180.

        private final int[][][] THRESHOLDS = new int[][][] {

                {{60, 165}, {165, 195}, {195, 300}},

                {{0, 45}, {45, 165}, {165, 195}, {330, 360}},

                {{0, 45}, {45, 135}, {225, 315}, {315, 360}},

                {{0, 30}, {165, 195}, {195, 315}, {315, 360}}

        };

        // Transform rotation ranges based on THRESHOLDS. This

        // has to be in step with THESHOLDS

        final int ROTATE_TO[][] = new int[][] {

        // See THRESHOLDS

        private final int[][] ROTATE_TO = new int[][] {

                {ROTATION_270, ROTATION_180, ROTATION_90},

                {ROTATION_0, ROTATION_270, ROTATION_180, ROTATION_0},

                {ROTATION_0, ROTATION_270, ROTATION_90, ROTATION_0},

                {ROTATION_0, ROTATION_180, ROTATION_90, ROTATION_0}

        };

        // Mapping into actual Surface rotation values

        final int TRANSFORM_ROTATIONS[] = new int[]{Surface.ROTATION_0,

                Surface.ROTATION_90, Surface.ROTATION_180, Surface.ROTATION_270};

        // Maximum absolute tilt angle at which to consider orientation changes.  Beyond this (i.e.

        // when screen is facing the sky or ground), we refuse to make any orientation changes.

        private static final int MAX_TILT = 65;

        // Additional limits on tilt angle to transition to each new orientation.  We ignore all

        // vectors with tilt beyond MAX_TILT, but we can set stricter limits on transition to a

        // particular orientation here.

        private final int[] MAX_TRANSITION_TILT = new int[] {MAX_TILT, MAX_TILT, 40, MAX_TILT};

        // Between this tilt angle and MAX_TILT, we'll allow orientation changes, but we'll filter

        // with a higher time constant, making us less sensitive to change.  This primarily helps

        // prevent momentary orientation changes when placing a device on a table from the side (or

        // picking one up).

        private static final int PARTIAL_TILT = 45;

        // Maximum allowable deviation of the magnitude of the sensor vector from that of gravity,

        // in m/s^2.  Beyond this, we assume the phone is under external forces and we can't trust

        // the sensor data.  However, under constantly vibrating conditions (think car mount), we

        // still want to pick up changes, so rather than ignore the data, we filter it with a very

        // high time constant.

        private static final int MAX_DEVIATION_FROM_GRAVITY = 1;

        // Actual sampling period corresponding to SensorManager.SENSOR_DELAY_NORMAL.  There's no

        // way to get this information from SensorManager.

        // Note the actual period is generally 3-30ms larger than this depending on the device, but

        // that's not enough to significantly skew our results.

        private static final int SAMPLING_PERIOD_MS = 200;

        // The following time constants are all used in low-pass filtering the accelerometer output.

        // See http://en.wikipedia.org/wiki/Low-pass_filter#Discrete-time_realization for

        // background.

        // When device is near-vertical (screen approximately facing the horizon)

        private static final int DEFAULT_TIME_CONSTANT_MS = 200;

        // When device is partially tilted towards the sky or ground

        private static final int TILTED_TIME_CONSTANT_MS = 600;

        // When device is under external acceleration, i.e. not just gravity.  We heavily distrust

        // such readings.

        private static final int ACCELERATING_TIME_CONSTANT_MS = 5000;

        private static final float DEFAULT_LOWPASS_ALPHA =

            (float) SAMPLING_PERIOD_MS / (DEFAULT_TIME_CONSTANT_MS + SAMPLING_PERIOD_MS);

        private static final float TILTED_LOWPASS_ALPHA =

            (float) SAMPLING_PERIOD_MS / (TILTED_TIME_CONSTANT_MS + SAMPLING_PERIOD_MS);

        private static final float ACCELERATING_LOWPASS_ALPHA =

            (float) SAMPLING_PERIOD_MS / (ACCELERATING_TIME_CONSTANT_MS + SAMPLING_PERIOD_MS);

        // The low-pass filtered accelerometer data

        private float[] mFilteredVector = new float[] {0, 0, 0};

        int getCurrentRotation() {

            return TRANSFORM_ROTATIONS[mRotation];

            return SURFACE_ROTATIONS[mRotation];

        }

        private void calculateNewRotation(int orientation, int zyangle) {

            if (localLOGV) Log.i(TAG, orientation + ", " + zyangle + ", " + mRotation);

            int rangeArr[][] = THRESHOLDS[mRotation];

        private void calculateNewRotation(int orientation, int tiltAngle) {

            if (localLOGV) Log.i(TAG, orientation + ", " + tiltAngle + ", " + mRotation);

            int thresholdRanges[][] = THRESHOLDS[mRotation];

            int row = -1;

            for (int i = 0; i < rangeArr.length; i++) {

                if ((orientation >= rangeArr[i][0]) && (orientation < rangeArr[i][1])) {

            for (int i = 0; i < thresholdRanges.length; i++) {

                if (orientation >= thresholdRanges[i][0] && orientation < thresholdRanges[i][1]) {

                    row = i;

                    break;

                }

            }

            if (row != -1) {

                // Find new rotation based on current rotation value.

                // This also takes care of irregular rotations as well.

            if (row == -1) return; // no matching transition

            int rotation = ROTATE_TO[mRotation][row];

            if (tiltAngle > MAX_TRANSITION_TILT[rotation]) {

                // tilted too far flat to go to this rotation

                return;

            }

            if (localLOGV) Log.i(TAG, " new rotation = " + rotation);

                if (rotation != mRotation) {

            mRotation = rotation;

                    // Trigger orientation change

                    onOrientationChanged(TRANSFORM_ROTATIONS[rotation]);

            onOrientationChanged(SURFACE_ROTATIONS[rotation]);

        }

        private float lowpassFilter(float newValue, float oldValue, float alpha) {

            return alpha * newValue + (1 - alpha) * oldValue;

        }

        private float vectorMagnitude(float x, float y, float z) {

            return (float) Math.sqrt(x*x + y*y + z*z);

        }

        /**

         * Absolute angle between upVector and the x-y plane (the plane of the screen), in [0, 90].

         * 90 degrees = screen facing the sky or ground.

         */

        private float tiltAngle(float z, float magnitude) {

            return Math.abs((float) Math.asin(z / magnitude) * RADIANS_TO_DEGREES);

        }

        public void onSensorChanged(SensorEvent event) {

            float[] values = event.values;

            float X = values[_DATA_X];

            float Y = values[_DATA_Y];

            float Z = values[_DATA_Z];

            float OneEightyOverPi = 57.29577957855f;

            float gravity = (float) Math.sqrt(X*X+Y*Y+Z*Z);

            float zyangle = (float)Math.asin(Z/gravity)*OneEightyOverPi;

            if ((zyangle <= PIVOT_UPPER) && (zyangle >= PIVOT_LOWER)) {

                // Check orientation only if the phone is flat enough

                // Don't trust the angle if the magnitude is small compared to the y value

                float angle = (float)Math.atan2(Y, -X) * OneEightyOverPi;

                int orientation = 90 - Math.round(angle);

                // normalize to 0 - 359 range

                while (orientation >= 360) {

                    orientation -= 360;

                }

                while (orientation < 0) {

                    orientation += 360;

            // the vector given in the SensorEvent points straight up (towards the sky) under ideal

            // conditions (the phone is not accelerating).  i'll call this upVector elsewhere.

            float x = event.values[_DATA_X];

            float y = event.values[_DATA_Y];

            float z = event.values[_DATA_Z];

            float magnitude = vectorMagnitude(x, y, z);

            float deviation = Math.abs(magnitude - SensorManager.STANDARD_GRAVITY);

            float tiltAngle = tiltAngle(z, magnitude);

            float alpha = DEFAULT_LOWPASS_ALPHA;

            if (tiltAngle > MAX_TILT) {

                return;

            } else if (deviation > MAX_DEVIATION_FROM_GRAVITY) {

                alpha = ACCELERATING_LOWPASS_ALPHA;

            } else if (tiltAngle > PARTIAL_TILT) {

                alpha = TILTED_LOWPASS_ALPHA;

            }

                calculateNewRotation(orientation, Math.round(zyangle));

            x = mFilteredVector[0] = lowpassFilter(x, mFilteredVector[0], alpha);

            y = mFilteredVector[1] = lowpassFilter(y, mFilteredVector[1], alpha);

            z = mFilteredVector[2] = lowpassFilter(z, mFilteredVector[2], alpha);

            magnitude = vectorMagnitude(x, y, z);

            tiltAngle = tiltAngle(z, magnitude);

            // Angle between the x-y projection of upVector and the +y-axis, increasing

            // counter-clockwise.

            // 0 degrees = speaker end towards the sky

            // 90 degrees = left edge of device towards the sky

            float orientationAngle = (float) Math.atan2(-x, y) * RADIANS_TO_DEGREES;

            int orientation = Math.round(orientationAngle);

            // atan2 returns (-180, 180]; normalize to [0, 360)

            if (orientation < 0) {

                orientation += 360;

            }

            calculateNewRotation(orientation, Math.round(tiltAngle));

        }

        public void onAccuracyChanged(Sensor sensor, int accuracy) {

    /**

     * Called when the rotation view of the device has changed.

     * Can be either Surface.ROTATION_90 or Surface.ROTATION_0.

     * @param rotation The new orientation of the device.

     *

     *  @see #ORIENTATION_UNKNOWN

     * @param rotation The new orientation of the device, one of the Surface.ROTATION_* constants.

     * @see Surface

     */

    abstract public void onOrientationChanged(int rotation);

}