method detect reverse portrait

detect device reverse portrait

    private SensorManager mSensorManager;
    private Sensor mOrientation;

    boolean Upsidedown = false;

    float value_0 = -10000;
    float value_1 = -10000;
    float deviceRotation = 0.0f;
    boolean ispotrait = false;
    
    
    public float calcAng(float x, float y) {
        if (y >= 0.0f) {
            if (x < 0.0f) {
                return (float) (180.0d - ((Math.atan((double) (y / (-x))) / 3.141592653589793d) * 180.0d));
            }
            if (x == 0.0f) {
                return 90.0f;
            }
            return (float) ((Math.atan((double) (y / x)) / 3.141592653589793d) * 180.0d);
        } else if (x < 0.0f) {
            return (float) (((Math.atan((double) (y / x)) / 3.141592653589793d) * 180.0d) + 180.0d);
        } else {
            if (x == 0.0f) {
                return 270.0f;
            }
            return (float) (360.0d - ((Math.atan((double) ((-y) / x)) / 3.141592653589793d) * 180.0d));
        }
    }



    private SensorEventListener mOrientationSensorListener = new SensorEventListener() {
        int orientation = -1;

        @Override
        public void onSensorChanged(SensorEvent event) {

            float Theta = 0.0f;
            float aX = event.values[0];
            float aY = event.values[1];
            float aZ = event.values[2];
            float Rmag = (float) Math.sqrt((double) (((aX * aX) + (aY * aY)) + (aZ * aZ)));
            if (Rmag > 0.0f) {
                Theta = (float) ((Math.acos((double) (aZ / Rmag)) / 3.141592653589793d) * 180.0d);
            }
            float Phi = (90.0f + calcAng(aX, aY)) + deviceRotation;
            while (Phi < 0.0f) {
                Phi += 360.0f;
            }
            while (Phi > 360.0f) {
                Phi -= 360.0f;
            }
            if ((Phi > 320.0f || Phi < 40.0f) && Theta > 45.0f && Theta < 135.0f) {
                //revese portrait
                //this.Upsidedown = true;
                if (state.equalsIgnoreCase("is_playing")){
                    pauseCountDown();
                    beginCountUP();
                }
            } else {
                //portrait
                //this.Upsidedown = false;
                if (state.equalsIgnoreCase("begin_countup_isplaying")){
                    cancelCountUp();
                    continueCountDown();
                }
            }

        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {

        }
    };
    
    
    
    
    how to use ?
    // Get sensor manager
        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        // Get the default sensor of specified type
        mOrientation = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

        mSensorManager.registerListener(mOrientationSensorListener, mOrientation,
                SensorManager.SENSOR_DELAY_GAME);