Google Play服务位置API-计数距离

Question

I've been following the https://developer.android.com/training/location/index.html tutorial.

Here's my class implementing the new Google's Location API:

public class GPSTracker implements LocationListener, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
    private final Context context;
    private TextView distanceTextView;
    private GoogleApiClient mGoogleApiClient;
    private LocationRequest mLocationRequest;
    private Location mLastLocation;
    private double totalMeters = 0;

    public GPSTracker(Context context, TextView distanceTextView) {
        this.context = context;
        this.distanceTextView = distanceTextView;
        buildGoogleApiClient();
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(context)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();

        mGoogleApiClient.connect();
    }

    @Override
    public void onLocationChanged(Location location) {
        double distance = mLastLocation.distanceTo(location);
        mLastLocation = location;
        totalMeters += distance;
        distanceTextView.setText(totalMeters + "");
    }

    @Override
    public void onConnected(Bundle bundle) {
        mLocationRequest = LocationRequest.create();
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
        mLocationRequest.setInterval(1000); // Update location every second

        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);

        mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Toast.makeText(context, connectionResult.getErrorMessage(), Toast.LENGTH_SHORT).show();
    }
}

Everything seems to be working flawlessly, but when my phone is not moving at all the totalDistance is still rising by 0.2-0.3 meters every time an onLocationChanged method is executed.

Any solution to prevent this situation is highly appreciated.

Answer 1

Don't forget that GPS is not pin point accurate. There will often be off by a few meters so it's natural that there are incorrect readings like this. While the old LocationManager had a minDistance settings, LocationRequest unfortunately does not.

Several solutions: You can check the speed, if the speed is zero, that probably indicates that the user actually hasn't moved. You can also manually check if the old location is almost the same as the new one (in your case 0.3m seems a good threshold) and discard that reading. Last but not least you can set up an ActivityRecognitionApi activity listener to determine if the user is actually moving or still.