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I build an app which use GMaps with several markers. The user can add or delete markers but my problem is to select the good zoom level to display all the markers.

That zoom level can change if the user add or delete markers.

For centering the camera I use the following code :

double xMin = 90.0 ;
double xMax =  0.0 ;
double yMin = 90.0 ;
double yMax =  0.0 ;

LatLngBounds.Builder builder = new LatLngBounds.Builder();

for (Place place : places) {
                if (place.getLatitude() < xMin)
                    xMin = place.getLatitude();

                if (place.getLatitude() > xMax)
                    xMax = place.getLatitude();

                if (place.getLongitude() < yMin)
                    yMin = place.getLongitude();

                if (place.getLongitude() > yMax)
                    yMax = place.getLongitude();

                MarkerOptions markerOptions = new MarkerOptions();
                markerOptions.position(new LatLng(place.getLatitude(), place.getLongitude()));
                markerOptions.title(String.valueOf(place.getId()));
                Marker marker = this.googleMap.addMarker(markerOptions);
                allMarkersMap.put(marker, place);
                displayMarkersMap.put(marker, place);
                builder.include(marker.getPosition());
            }

            double xPos = (xMax + xMin) / 2;
            double yPos = (yMax + yMin) / 2;

            LatLngBounds bounds = builder.build();
            int padding = 1; // offset from edges of the map in pixels
            //CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngBounds(bounds, padding);
            //this.googleMap.moveCamera(cameraUpdate);
            LatLng latLng = new LatLng(xPos, yPos);
            CameraPosition cameraPosition = new CameraPosition.Builder().target(latLng).zoom(2).build();
            this.googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

But I don't find a solution to have a good zoom value.

Fred37b
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  • I think that the best option is using the `CameraUpdateFactory.newLatLngBounds(bounds, padding);` that you have commented in your code – antonio Sep 28 '16 at 11:15
  • Ok, but how select dynamically a good zoom level ? I want to select a zoom level which display all the markers on the map – Fred37b Sep 29 '16 at 08:21

2 Answers2

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I understand that you need to define a center for your map and ensure that all your markers are within the view.

In this case you can compute the LatLngBounds that include your markers and then extend it using the SphericalUtil.computeOffset, SphericalUtil.computeDistanceBetween and SphericalUtil.computeHeading methods from the Google Maps API Utility Library

private LatLngBounds findBounds(List<LatLng> positions, LatLng center) {
    // Add all the positions to a LatLngBounds (including center)
    LatLngBounds.Builder boundsBuilder = new LatLngBounds.Builder();
    for (LatLng position : positions) {
        boundsBuilder.include(position);
    }
    boundsBuilder.include(center);
    LatLngBounds bounds = boundsBuilder.build();

    // Compute the farthest location from the center among the bound corners
    LatLng northWest = new LatLng(bounds.northeast.latitude, bounds.southwest.longitude);
    LatLng southEast = new LatLng(bounds.southwest.latitude, bounds.northeast.longitude);
    LatLng farthest = findFarthestLocation(center, bounds.northeast, northWest, southEast, bounds.southwest);

    // Expand the bounds adding the projection of the farthest location from the center
    // in the oposite direction
    bounds = bounds.including(SphericalUtil.computeOffset(center,
            SphericalUtil.computeDistanceBetween(center, farthest),
            SphericalUtil.computeHeading(center, farthest) + 180));

    return bounds;
}

private LatLng findFarthestLocation(LatLng from, LatLng... locations) {
    LatLng farthest = null;

    for (LatLng location : locations) {
        if (farthest == null ||
                SphericalUtil.computeDistanceBetween(from, location) > SphericalUtil.computeDistanceBetween(from, farthest)) {
            farthest = location;
        }
    }

    return farthest;
}

You can test this method doing 

LatLng center = new LatLng(40.384213, -3.875244);
List<LatLng> positions = new ArrayList<>();
positions.add(new LatLng(43.153102, 2.914307));
positions.add(new LatLng(42.976521, 1.508057));
positions.add(new LatLng(42.492353, 0.123779));

Display display = getActivity().getWindowManager().getDefaultDisplay();
                Point size = new Point();
                display.getSize(size);
                int width  = size.x;
                int height = size.y;

LatLngBounds bounds = findBounds(positions,center);
mMap.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds,width,height,10));
Fred37b
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antonio
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  • You don't need to select a zoom level, using this code the view will be automatilcally adjusted to show all the markers ensuring that the map is centered at the desired point – antonio Oct 06 '16 at 08:07
  • Ok, it seems to work but I have an exception, IllegalStateException which it throw because I havn't calculated my screen size. – Fred37b Oct 06 '16 at 08:49
  • This is a known issue. Here you can find the solution/workaround: http://stackoverflow.com/questions/13692579/movecamera-with-cameraupdatefactory-newlatlngbounds-crashes – antonio Oct 06 '16 at 08:51
  • Yes it helps but I must find the size of my map view instead of the screen, I'm not in full screen so it works but not perfectly – Fred37b Oct 06 '16 at 09:44
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map.setMapType(GoogleMap.MAP_TYPE_TERRAIN);
CameraUpdate update = CameraUpdateFactory.newLatLngZoom(LOCATION_MYPOSITION, 16);
map.animateCamera(update);

Try this , i think 16 zoom will be enough to see the markers

GrIsHu
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Hemant Ukey
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  • I want to choose dynamically the zoom level in function of markers' position, I can't select myself a value for the zoom level. – Fred37b Sep 28 '16 at 13:01