Automatically calculate map bounds from a list of LatLng values

[KingWu]

Just read the source code. Cannot find a method to build a LatLngBounds from a list of LatLng.

https://developers.google.com/android/reference/com/google/android/gms/maps/model/LatLngBounds.Builder

[adim86]

I am having the same issue, I want to build the bounds from a couple of Latitude and Longitude Coordinates but I am unable to find how to implement this in FLutter with the classes we have been given. Any ideas?

[unamed000]

same issue. We need to calculate the zoom and bounds of the map between 2 markers

[adim86]

@unamed000 I was able to solve this by adding this function and using it to calculate

LatLngBounds boundsFromLatLngList(List<LatLng> list) {
    assert(list.isNotEmpty);
    double x0, x1, y0, y1;
    for (LatLng latLng in list) {
      if (x0 == null) {
        x0 = x1 = latLng.latitude;
        y0 = y1 = latLng.longitude;
      } else {
        if (latLng.latitude > x1) x1 = latLng.latitude;
        if (latLng.latitude < x0) x0 = latLng.latitude;
        if (latLng.longitude > y1) y1 = latLng.longitude;
        if (latLng.longitude < y0) y0 = latLng.longitude;
      }
    }
    return LatLngBounds(northeast: LatLng(x1, y1), southwest: LatLng(x0, y0));
  }

[unamed000]

Hi @adim86,
So the northeast should be the maximum number of lat + lng and southwest should be minimum ?

Edit: Thanks adim,
It's working like a charm :), when using with

_mapController.animateCamera(CameraUpdate.newLatLngBounds(
                  LatLngBounds(
                      southwest: LatLng(latMin, longMin),
                      northeast: LatLng(latMax, longMax),
                  ),
                  100
                ));

[Nexuist]

While @adim86's solution works like a charm, I still believe it should be part of the standard API to maintain feature parity with the Google Maps JS SDK. Additionally, LatLngBounds should have a .getCenter() method like its JS counterpart does.

For me this would be useful as I'm trying to make the map show all markers at once, so I need to make a bounds that includes every marker and also dispatch a camera update that sets the target and zoom to adequate values such that the map shows every marker.

[sanisloandras]

I also need this feature, but sadly don't have the time to help in development.

[karatasemre]

@adim86 thank youuuuuuuu

[DanielFortuyn]

@Nexuist Yeah that is actually somehting that I would like to achieve as well, did you manage to get something like that working by now?

[Nexuist]

@DanielFortuyn Yes, I did using some custom code mixed and matched from SO:

LatLngBounds boundsFromLatLngList(List<LatLng> list) {
  double x0, x1, y0, y1;
  for (LatLng latLng in list) {
    if (x0 == null) {
      x0 = x1 = latLng.latitude;
      y0 = y1 = latLng.longitude;
    } else {
      if (latLng.latitude > x1) x1 = latLng.latitude;
      if (latLng.latitude < x0) x0 = latLng.latitude;
      if (latLng.longitude > y1) y1 = latLng.longitude;
      if (latLng.longitude < y0) y0 = latLng.longitude;
    }
  }
  return LatLngBounds(northeast: LatLng(x1, y1), southwest: LatLng(x0, y0));
}

 void _onMapCreated(GoogleMapController controller) {
    _controller.complete(controller);
    Future.delayed(
        Duration(milliseconds: 200),
        () => controller.animateCamera(CameraUpdate.newLatLngBounds(
            boundsFromLatLngList(
                widget.locations.values.map((loc) => loc.asLatLng()).toList()),
            1)));
  }

[pkill37]

@Nexuist Thanks for the Future.delayed snippet, I used this to work around the fact that newLatLngBounds was randomly throwing for me

E/MethodChannel#plugins.flutter.io/google_maps_14( 8309): com.google.maps.api.android.lib6.common.apiexception.c: Error using newLatLngBounds(LatLngBounds, int): Map size can't be 0. Most likely, layout has not yet occured for the map view.  Either wait until layout has occurred or use newLatLngBounds(LatLngBounds, int, int, int) which allows you to specify the map's dimensions.

even though the map should be all ready in onMapReady.

[giorgio79]

Google team committed a getVisibleRegion method, would that be the way forward? #25755

[jose-airspace]

@Nexuist how did you get the appropriate zoom level though?

Nvm, it auto zooms. Unfortunate that you can't set it in the initializer which what was broken for me. Whats the point of cameraTargetBounds?!

[velval]

One can use the LatLngBounds.fromPoints(points) built-in method if using the flutter_map library.

[khurram-saeed-malik]

Here is a re-written version of @Nexuist suggestion as an extension function to LatLngBounds class:

extension LatLngBoundsExtension on LatLngBounds {
  static fromLatLng(List<LatLng> latLngList) {
      assert(latLngList.isNotEmpty);
      double? x0, x1, y0, y1;
      for (LatLng latLng in latLngList) {
        if (x0 == null) {
          x0 = x1 = latLng.latitude;
          y0 = y1 = latLng.longitude;
        } else {
          if (latLng.latitude > x1!) x1 = latLng.latitude;
          if (latLng.latitude < x0) x0 = latLng.latitude;
          if (latLng.longitude > y1!) y1 = latLng.longitude;
          if (latLng.longitude < y0!) y0 = latLng.longitude;
        }
      }
      return LatLngBounds(northeast: LatLng(x1!, y1!), southwest: LatLng(x0!, y0!));
  }
}

Usage:

LatLngBoundsExtension.fromLatLng(markers.map((e) => e.position).toList()), 1)

[tomheno]

Null-safe version of @adim86 solution :

LatLngBounds boundsFromLatLngList(List<LatLng> list) {
  double? x0, x1, y0, y1;
  for (LatLng latLng in list) {
    if (x0 == null || x1 == null || y0 == null || y1 == null) {
      x0 = x1 = latLng.latitude;
      y0 = y1 = latLng.longitude;
    } else {
      if (latLng.latitude > x1) x1 = latLng.latitude;
      if (latLng.latitude < x0) x0 = latLng.latitude;
      if (latLng.longitude > y1) y1 = latLng.longitude;
      if (latLng.longitude < y0) y0 = latLng.longitude;
    }
  }

  return LatLngBounds(LatLng(x1!, y1!), LatLng(x0!, y0!));
}

[Daeon97]

@unamed000 I was able to solve this by adding this function and using it to calculate

LatLngBounds boundsFromLatLngList(List<LatLng> list) {
    assert(list.isNotEmpty);
    double x0, x1, y0, y1;
    for (LatLng latLng in list) {
      if (x0 == null) {
        x0 = x1 = latLng.latitude;
        y0 = y1 = latLng.longitude;
      } else {
        if (latLng.latitude > x1) x1 = latLng.latitude;
        if (latLng.latitude < x0) x0 = latLng.latitude;
        if (latLng.longitude > y1) y1 = latLng.longitude;
        if (latLng.longitude < y0) y0 = latLng.longitude;
      }
    }
    return LatLngBounds(northeast: LatLng(x1, y1), southwest: LatLng(x0, y0));
  }

So I am trying to implement exactly this right now. Fortunately stumbled on this issue here. Thanks @adim86 for this. Works perfectly