We’re building a Django application at work, and I had to implement a
way for a user to select a location on a map, in order to be able to
save the exact coordinates and the zoom level the user chose.
I looked around to see if something similar had been developed, but I
did not find anything so simple and useful as what I later developed, so
for the sake of open source-ness I’m sharing it here with you.
It is implemented as a standard Django form widget so just do as any
other Django widget, for example:
class PersonForm(forms.Form):
name = forms.CharField()
website = forms.URLField()
location = forms.CharField(widget=GMapInput(attrs={'width':'600', 'height':'400'}))
Here’s the code for the GMapInput class (sorry for the docs in
Spanish, but I’m in Mexico):
from django.forms.widgets import Input
from django.utils.safestring import mark_safe
class GMapInput(Input):
"""
Widget para seleccionar un punto en un mapa de Google
"""
def render(self, name, value, attrs=None):
"""
Atributos extras:
- width: ancho del mapa en pixeles
- height: alto del mapa en pixeles
- center: latitud,longitud del punto central del mapa
- zoom: zoom inicial del mapa, 1 - 17
"""
final_attrs = self.build_attrs(attrs)
width = final_attrs['width'] if 'width' in final_attrs else '500'
height = final_attrs['height'] if 'height' in final_attrs else '300'
center = final_attrs['center'] if 'center' in final_attrs else '21.983801,-100.964355' # Centro de México
zoom = final_attrs['zoom'] if 'zoom' in final_attrs else '4' # Zoom amplio, se ve todo un país
widget = u'''<div style="margin-left:7em; padding-left:30px;">
<input type="hidden" value="%(value)s" name="%(name)s" id="%(id)s" />
<div id="%(id)s_map" style="width: %(width)spx; height: %(height)spx"></div></div>
<script type="text/javascript">
var %(id)s_map = new GMap2(document.getElementById("%(id)s_map"));
%(id)s_map.addControl(new GLargeMapControl3D());
var %(id)s_marker;
function %(id)s_updateField() {
document.getElementById("%(id)s").value = %(id)s_marker.getLatLng().toUrlValue() + "|" + %(id)s_map.getZoom();
%(id)s_map.panTo(%(id)s_marker.getLatLng(), true);
}
''' % { 'value': value, 'name': name, 'id': final_attrs['id'], 'width': width, 'height': height }
if value is None or value == '':
widget = widget + u'''
%(id)s_map.setCenter(new GLatLng(%(center)s), %(zoom)s);
var %(id)s_clickListener = GEvent.addListener(%(id)s_map, "click", function(overlay, latlng) {
if(latlng) {
%(id)s_marker = new GMarker(latlng, {draggable: true});
%(id)s_map.addOverlay(%(id)s_marker);
%(id)s_updateField();
GEvent.addListener(%(id)s_marker, "dragend", %(id)s_updateField);
GEvent.addListener(%(id)s_map, "zoomend", %(id)s_updateField);
GEvent.addListener(%(id)s_map, "dblclick", function (overlay, latlng) { %(id)s_marker.setLatLng(latlng); %(id)s_updateField(); });
GEvent.removeListener(%(id)s_clickListener);
}
});
</script>''' % { 'id': final_attrs['id'], 'center': center, 'zoom': zoom }
else:
values = value.partition('|')
widget = widget + u'''
%(id)s_map.setCenter(new GLatLng(%(coords)s), %(zoom)s);
%(id)s_marker = new GMarker(new GLatLng(%(coords)s), {draggable: true});
%(id)s_map.addOverlay(%(id)s_marker);
GEvent.addListener(%(id)s_marker, "dragend", %(id)s_updateField);
GEvent.addListener(%(id)s_map, "zoomend", %(id)s_updateField);
GEvent.addListener(%(id)s_map, "dblclick", function (overlay, latlng) { %(id)s_marker.setLatLng(latlng); %(id)s_updateField(); });
''' % { 'id': final_attrs['id'], 'coords': values[0], 'zoom': values[2] }
return mark_safe(widget)
Don’t forget to add the <script> tag linking to the Google Maps
API.
It is yet far from perfect, but I still hope it helps someone out
there.