ReactNativeHeadingModule.java

package com.joshblour.reactnativeheading;

import android.app.Activity;
import android.app.Application;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.ParcelUuid;
import android.util.Log;


import com.facebook.react.bridge.Arguments;
import com.facebook.react.bridge.Promise;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;
import com.facebook.react.bridge.WritableArray;
import com.facebook.react.bridge.WritableMap;
import com.facebook.react.modules.core.DeviceEventManagerModule;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;


public class ReactNativeHeadingModule extends ReactContextBaseJavaModule implements SensorEventListener {


    private static Context mApplicationContext;
    private int mAzimuth = 0; // degree
    private int newAzimuth = 0; // degree
    private int mFilter = 5;
    private SensorManager mSensorManager;
    private Sensor mSensor;
    private float[] orientation = new float[3];
    private float[] rMat = new float[9];

    public ReactNativeHeadingModule(ReactApplicationContext reactContext) {
        super(reactContext);
        mApplicationContext = reactContext.getApplicationContext();
    }

    @Override
    public String getName() {
        return "ReactNativeHeading";
    }

    @ReactMethod
    public void start(int filter, Promise promise) {

        if (mSensorManager == null) {
            mSensorManager = (SensorManager) mApplicationContext.getSystemService(Context.SENSOR_SERVICE);
        }

        if (mSensor == null) {
            mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ROTATION_VECTOR);
        }

        mFilter = filter;
        boolean started = mSensorManager.registerListener(this, mSensor, SensorManager.SENSOR_DELAY_UI);
        promise.resolve(started);
    }

    @ReactMethod
    public void stop() {
        mSensorManager.unregisterListener(this);
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        if( event.sensor.getType() == Sensor.TYPE_ROTATION_VECTOR ){
            // calculate th rotation matrix
            SensorManager.getRotationMatrixFromVector(rMat, event.values);
            // get the azimuth value (orientation[0]) in degree
            newAzimuth = (int) (((( Math.toDegrees( SensorManager.getOrientation( rMat, orientation )[0] ) + 360 ) % 360) -
                          ( Math.toDegrees( SensorManager.getOrientation( rMat, orientation )[2] ))) +360) % 360;
            //dont react to changes smaller than the filter value
            if (Math.abs(mAzimuth - newAzimuth) < mFilter) {
                return;
            }

            getReactApplicationContext()
                    .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
                    .emit("headingUpdated", (int) newAzimuth);

            mAzimuth = newAzimuth;
            // Log.e("Azimuth",
            //   String.valueOf(newAzimuth));
            
        }
    }


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

    }
}