LocationTrackerActivity.java

public class LocationTrackerActivity extends AppCompatActivity implements
                                GoogleApiClient.ConnectionCallbacks,
                                GoogleApiClient.OnConnectionFailedListener,
                                LocationListener

 {

     private static final String TAG = "LocationTrackerActivity";

     private static final int REQUEST_CHECK_SETTINGS = 0x1;

     private static final long UPDATE_INTERVAL_IN_MILLISECONDS = 5000;

     private static final long FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS =
            UPDATE_INTERVAL_IN_MILLISECONDS / 2;


     private GoogleApiClient mGoogleApiClient;

     private LocationRequest mLocationRequest;
     
     private LocationSettingsRequest mLocationSettingsRequest;

     private String mLastUpdateTime;

     private Location mCurrentLocation;


     protected final PublishRelay<Location> relay = PublishRelay.create();




    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Log.d(TAG, "onCreate: ");


        buildGoogleApiClient();
        createLocationRequest();
        buildLocationSettingsRequest();

    }



     public Location getmCurrentLocation(){
         if(mCurrentLocation!=null){
             return mCurrentLocation;
         }
         return null;
     }





    protected synchronized void buildGoogleApiClient() {
        Log.i(TAG, "Building GoogleApiClient");
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }


    protected void createLocationRequest() {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(UPDATE_INTERVAL_IN_MILLISECONDS);
        mLocationRequest.setFastestInterval(FASTEST_UPDATE_INTERVAL_IN_MILLISECONDS);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }


    protected void buildLocationSettingsRequest() {
        LocationSettingsRequest.Builder builder = new LocationSettingsRequest.Builder();
        builder.addLocationRequest(mLocationRequest);
        mLocationSettingsRequest = builder.build();
    }


    protected void checkLocationSettingsAndStartLocationUpdates() {

        PendingResult<LocationSettingsResult> result =
                LocationServices.SettingsApi.checkLocationSettings(
                        mGoogleApiClient,
                        mLocationSettingsRequest
                );
        result.setResultCallback(new ResultCallback<LocationSettingsResult>() {
            @Override
            public void onResult(@NonNull LocationSettingsResult locationSettingsResult) {
                final Status status = locationSettingsResult.getStatus();
                switch (status.getStatusCode()) {
                    case LocationSettingsStatusCodes.SUCCESS:

                        Log.i(TAG, "All location settings are satisfied.");
                        startLocationUpdates();

                        break;
                    case LocationSettingsStatusCodes.RESOLUTION_REQUIRED:
                        Log.i(TAG, "Location settings are not satisfied. Show the user a dialog to" +
                                "upgrade location settings ");
                        try {
                            // Show the dialog by calling startResolutionForResult(), and check the result
                            // in onActivityResult().
                            status.startResolutionForResult(LocationTrackerActivity.this, REQUEST_CHECK_SETTINGS);

                        } catch (IntentSender.SendIntentException e) {
                            Log.i(TAG, "PendingIntent unable to execute request.");
                        }
                        break;
                    case LocationSettingsStatusCodes.SETTINGS_CHANGE_UNAVAILABLE:
                        Log.i(TAG, "Location settings are inadequate, and cannot be fixed here. Dialog " +
                                "not created.");
                        break;
                }
            }
        });  // call on onResult
    }




    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        switch (requestCode) {
            // Check for the integer request code originally supplied to startResolutionForResult().
            case REQUEST_CHECK_SETTINGS:
                switch (resultCode) {
                    case Activity.RESULT_OK:
                        Log.i(TAG, "User agreed to make required location settings changes.");
                        startLocationUpdates();
                        break;
                    case Activity.RESULT_CANCELED:
                        Log.i(TAG, "User chose not to make required location settings changes.");
                        break;
                }
                break;
        }
    }




    protected void startLocationUpdates() {

        Log.d(TAG, "startLocationUpdates: ");

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
             return;
        }

        LocationServices.FusedLocationApi.requestLocationUpdates(
                mGoogleApiClient,
                mLocationRequest,

                this                    ////  call onLocationChanged
        );

    }




    protected void stopLocationUpdates() {

        LocationServices.FusedLocationApi.removeLocationUpdates(
                mGoogleApiClient,
                this
        );
    }

    @Override
    protected void onStart() {
        super.onStart();

        if(mGoogleApiClient!=null)
         mGoogleApiClient.connect();
    }

    @Override
    public void onResume() {
        super.onResume();

        Log.d(TAG, "onResume: ");

        if (mGoogleApiClient!=null && mGoogleApiClient.isConnected() ) {
            Log.d(TAG, "onResume: mGoogleApiClient isConnected");
            checkLocationSettingsAndStartLocationUpdates();
        }
        else if(mGoogleApiClient!=null && !mGoogleApiClient.isConnecting()) {
            mGoogleApiClient.connect();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        // Stop location updates to save battery, but don't disconnect the GoogleApiClient object.
        if (mGoogleApiClient!=null && mGoogleApiClient.isConnected()) {
            Log.d(TAG, "onPause: ");
            stopLocationUpdates();
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG, "onStop: ");
        if(mGoogleApiClient!=null)
        mGoogleApiClient.disconnect();
    }

    /**
     * Runs when a GoogleApiClient object successfully connects.
     */
    @Override
    public void onConnected(Bundle connectionHint) {

        Log.i(TAG, "Connected to GoogleApiClient");

        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }

        mCurrentLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);


        if(mCurrentLocation!=null)
         relay.accept(mCurrentLocation);

        checkLocationSettingsAndStartLocationUpdates();


    }


    @Override
    public void onLocationChanged(Location location) {

        Log.d(TAG, "onLocationChanged: ");

        mCurrentLocation = location;

        mLastUpdateTime = DateFormat.getTimeInstance().format(new Date());

        if(mCurrentLocation!=null)
            relay.accept(mCurrentLocation);

    }

    @Override
    public void onConnectionSuspended(int cause) {
        Log.i(TAG, "Connection suspended");
    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {

        Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = " + result.getErrorCode());
    }






}