How to use Magnetic Field Sensor?

coolphill

I can't figure out how to use the Magnetic field sensor, I may be completely dumb but take a look at this:

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

Context context;
SensorManager manager;
Sensor sensor;
float X1;
float Y1;
float Z1;

void setup() {
  fullScreen();

  context = getActivity();
  manager = (SensorManager)context.getSystemService(Context.SENSOR_SERVICE);
  sensor = manager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

 // manager.registerListener(listener, sensor, SensorManager.SENSOR_DELAY_GAME);
}
public void onSensorChanged(SensorEvent event)
     {
       X1 = event.values[0];
       Y1 = event.values[1];
       Z1 = event.values[2];
     }

void draw() {


  text(str(X1) + " " + str(Y1) + " " + str(Z1) , width/2, height/2);
}

All I get is 0.0, 0.0, 0.0 (And my phone does have the sensor) Does anyone know the proper way of doing this?

kfrajer

Please install the ketai library. Check the ketai.org website for an example.

Kf

clankill3r

Sad to see the library is programmed using the private keyword way to much... For the rest it seems nice, it would be nice if it would be integrated in the default android mode.

akenaton

@coolphill===

you dont need ketai but:

your code cannot run for a lot of reasons:

• first is that you dont get any context and so your sensor is null: you are in a fragment

• second is that you never add a listener to your sensor manager: it cannot return any values

• third is that you never clear your background in draw

here a snippet which will run (using your code and modifying it); in order to improve it you have to add onPause() && onResume() for registering and unregistering.

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

    Context context;
    SensorManager manager;
    Sensor sensor;

    float X1;
    float Y1;
    float Z1;


    void setup() {
      fullScreen();//better in settings()

      context = getActivity().getApplicationContext();//get the context from the //main activity
      manager = (SensorManager)context.getSystemService(Context.SENSOR_SERVICE);
      sensor = manager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);

     //verify wether the sensor is ok; if yes add a listener
     if (sensor != null) {
                manager.registerListener(listener, sensor,
                        SensorManager.SENSOR_DELAY_NORMAL);
               println("CAPTEUR", "ENREGISTREMENT DU CAPTEUR MAGNETIQUE");

            } else {

                println("SORRY!!!!-CE TELEPHONE N'A PAS DE CAPTEUR MAGNETIQUE");

            }
      };

  //adding the listener (two methods are mandatory from the interface) 

    public SensorEventListener listener = new SensorEventListener() {


            public void onAccuracyChanged(Sensor sensor, int accuracy) {
            }

           public void onSensorChanged(SensorEvent event)
         {
           float[] val = event.values;
           X1 = val[0];
           Y1 = val[1];
           Z1 = val[2];

         }
        };


    void draw() {
     background(255);//if you want to see your values

     textSize(36);//phone res is probably too high for using default!

     fill(255,0,0);
      text(str(X1) + " " + str(Y1) + " " + str(Z1) , width/2, height/2);
    }

kfrajer

@coolphill You can also check the sensor tutorial in the Processing Android website: http://android.processing.org/tutorials/sensors/index.html

Kf