I am a beginner in android and having some problem in handling NullPointerException.I need to pass the magnetometer reading values in an array from one class to a fragment. Here is the magnetometer class:
public class Magnetometer implements SensorEventListener {
private Sensor mag;
private SensorManager magman;
private boolean magAvailable;
private float[] magValue;
public Magnetometer(MagFragment context){
magman=(SensorManager)context.getActivity().getSystemService(Context.SENSOR_SERVICE);
magAvailable=magman.getDefaultSensor(Sensor.TYPE_ACCELEROMETER)!=null;
if(isMagAvailable()){
magValue=new float[3];
mag=magman.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
magman.registerListener(this,mag,SensorManager.SENSOR_DELAY_NORMAL);
}
}
@Override
public void onSensorChanged(SensorEvent event) {
for(int i=0;i<3;i++)
magValue[i]=event.values[i];
}
public float[] getLastReading(){
return this.magValue;
}
@Override
public void onAccuracyChanged(Sensor sensor, int i) {
}
public boolean isMagAvailable(){
return this.magAvailable;
}
public void unregister(){
if(isMagAvailable())
magman.unregisterListener(this,mag);
}
}
Here is the fragment:
ublic class MagFragment extends Fragment {
private Magnetometer mag;
private TextView x,y,z;
private float[] magValues;
public MagFragment() {
// Required empty public constructor
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//returning our layout file
//change R.layout.yourlayoutfilename for each of your fragments
View rootView = inflater.inflate(R.layout.fragment_mag, container, false);
x=(TextView) rootView.findViewById(R.id.mx);
y=(TextView) rootView.findViewById(R.id.my);
z=(TextView) rootView.findViewById(R.id.mz);
magValues=new float[3];
getData(this);
return rootView;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
//you can set the title for your toolbar here for different fragments different titles
getActivity().setTitle("Magnetometer");
}
public void getData(MagFragment context)
{
magValues=mag.getLastReading();
displayData(magValues);
}
public void displayData(float [] magV)
{
x.setText(String.valueOf(magV[0]));
y.setText(String.valueOf(magV[1]));
z.setText(String.valueOf(magV[2]));
}
}
I understand,that the function returns some NULL values. The error I get is "Attempt to invoke virtual method 'float[] com.example.ark.ark.Sensors.Magnetometer.getLastReading()' on a null object reference"
