How can I implement this class in my mainActivity

Question

I found this class to use a compass but in the site I found it they don´t explain how to implement it, I mean, when I make the call to the class in the main activity and put the result only put the results once and do not keep refreshing the screen with the values... here is the class I Found:

public class Compass implements SensorEventListener{

private SensorManager sensorManager;
private Sensor gsensor;
private Sensor msensor;
private float[] mGravity = new float[3];
private float[] mGeomagnetic = new float[3];
private float azimuth = 0f;
private float correctAzimuth = 0;

public Compass(Context context){
    sensorManager = (SensorManager) context
                    .getSystemService(Context.SENSOR_SERVICE);
    gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
    msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
}

@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];

            // mGravity = event.values;
            // Log.e(TAG, Float.toString(mGravity[0]));
        }

        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
            // mGeomagnetic = event.values;

            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];
            // Log.e(TAG, Float.toString(event.values[0]));

        }

        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);
            // Log.d(TAG, "azimuth (rad): " + azimuth);
            azimuth = (float) Math.toDegrees(orientation[0]); // orientation
            azimuth = (azimuth + 360) % 360;
            // Log.d(TAG, "azimuth (deg): " + azimuth);
        }
    }
}

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

}

}

Thanks in advance!! :)

Answer 1

I tried the code and it worked for me after I added

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_MOCK_LOCATION"/>

in the manifest. And added

    sensorManager.registerListener(this, gsensor, SensorManager.SENSOR_DELAY_NORMAL);
    sensorManager.registerListener(this, msensor, SensorManager.SENSOR_DELAY_NORMAL);

to the Compass constructor.

To access the compass value you need a getter method for the azimuth variable in the Compass class.

Compass.onCreate:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    Compass compass = new Compass(this);
}

MainActivity:

package com.example.myfirstapp;

import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.util.Log;

public class Compass implements SensorEventListener{

    private SensorManager sensorManager;
    private Sensor gsensor;
    private Sensor msensor;
    private float[] mGravity = new float[3];
    private float[] mGeomagnetic = new float[3];
    private float azimuth = 0f;
    private float correctAzimuth = 0;
    private String TAG = "Compass";

    public Compass(Context context)
    {
        sensorManager = (SensorManager) context
                    .getSystemService(Context.SENSOR_SERVICE);
        gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

        sensorManager.registerListener(this, gsensor, SensorManager.SENSOR_DELAY_NORMAL);
        sensorManager.registerListener(this, msensor, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @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];

                // mGravity = event.values;
                // Log.e(TAG, Float.toString(mGravity[0]));
            }

            if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) 
            {
                // mGeomagnetic = event.values;

                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];
                // Log.e(TAG, Float.toString(event.values[0]));

            }

            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);
                // Log.d(TAG, "azimuth (rad): " + azimuth);
                azimuth = (float) Math.toDegrees(orientation[0]); // orientation
                azimuth = (azimuth + 360) % 360;

                Log.d(TAG, "azimuth (deg): " + azimuth);
            }
        }
    }

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

    }

}