How to point arrow to only particular direction i.e. west

Question

I want to point my arrow view to only west direction no matter where the user is facing. Below is the code that I have tried but didn't get the desired result.

// inside onCreate()
sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
    gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
    packageManager = getPackageManager();
    if (packageManager.hasSystemFeature(PackageManager.FEATURE_SENSOR_COMPASS)){
        sensorManager.registerListener(this, gsensor, SensorManager.SENSOR_DELAY_GAME);
        sensorManager.registerListener(this, msensor, SensorManager.SENSOR_DELAY_GAME);
    }else {
        Toast.makeText(MainActivity.this,"No Compass Sensor !", Toast.LENGTH_SHORT).show();
    }


 @Override
public void onSensorChanged(SensorEvent event) {

    final float alpha = 0.97f;

    synchronized (this){
        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER){
            mGravity[0] = alpha * mGravity[0] + (1 - alpha)
                    * event.values[0];
            mGravity[1] = alpha * mGravity[1] + (1 - alpha)
                    * event.values[1];
            mGravity[2] = alpha * mGravity[2] + (1 - alpha)
                    * event.values[2];
        }

        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD){
            mGeomagnetic[0] = alpha * mGeomagnetic[0] + (1 - alpha)
                    * event.values[0];
            mGeomagnetic[1] = alpha * mGeomagnetic[1] + (1 - alpha)
                    * event.values[1];
            mGeomagnetic[2] = alpha * mGeomagnetic[2] + (1 - alpha)
                    * event.values[2];
        }

        float R[] = new float[9];
        float I[] = new float[9];
        boolean success = SensorManager.getRotationMatrix(R, I, mGravity, mGeomagnetic);
        if (success){
            float orientation[] = new float[3];
            SensorManager.getOrientation(R, orientation);
            azimuth = (float) Math.toDegrees(orientation[0]);
            Log.i("DegreeA",""+azimuth);
            azimuth = (azimuth + 360) % 270;
            Log.i("DegreeA",""+azimuth);
            adjustThearrow();
        }
    }
}

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

}

private void adjustThearrow(){


    Matrix matrix = new Matrix();
    imageview.setScaleType(ImageView.ScaleType.MATRIX);   
    matrix.postRotate((float) -azimuth, imageview.getDrawable().getBounds().width()/2,
            imageview.getDrawable().getBounds().height()/2);

    imageview.setImageMatrix(matrix);
}

In the below line of code, if I set 360 instead of 270, it gives me an arrow pointing to only north direction and it rotates smoothly.

azimuth = (azimuth + 360) % 360;

But if I want my code to face the arrow only to west direction, I have set the code like this:

azimuth = (azimuth + 360) % 270;

but this time the rotation is not smoother.

Kindly help me on how to proceed. It would be better if any alternative solution will be provided.