Question

I am using Google Maps API v3 on a website I am developing. I have a drop-down box beneath my map which allows the user to switch between different sets of markers to be displayed on the map. Each marker is displayed using marker.setMap().

My problem is that the map sometimes takes a long time to display the new markers, especially in IE. I want to show a “Loading” animation while the map is switching markers. But I don’t know how to detect when the map has finished displaying the new data (there is no page load, since this is all AJAX). Is there a callback or event listener for a setMap() event, so I can call a function to stop the “Loading” animation when the last marker has finished loading?

Answer 1

There doesn’t seem to be a callback or event listener for setMap(), but I figured out a way to accomplish what I wanted. I am loading the Google Map using jQuery. Here is my code.

When initializing the map, I set up a listener for the ‘idle’ event, which hides the “loading” animation. The ‘idle’ event is triggered whenever the map is finished redrawing after a scroll or zoom change:

google.maps.event.addListener(this.map, 'idle', function() {
 $('#loading').hide();
});

And in my function to clear overlays, I first show the loading animation, then clear each marker using setMap(null). Then I very slightly recenter the map by changing the longitude by .000000001. This happens after all the setMap() calls, and triggers the ‘idle’ event which hides the loading animation.

// clear overlays from the map
function clearOverlays() {
 $('#loading').show();

 // clear the markers from the active data array
 if (activeData) {
  for (i in activeData) { activeData[i].setMap(null); }
 }
 activeData = '';

 // very slightly recenter the map to trigger the 'idle' event
 var centerlat = MYMAP.map.getCenter().lat();
 var centerlng = MYMAP.map.getCenter().lng() + .000000001;
 recenter = new google.maps.LatLng(centerlat, centerlng);
 MYMAP.map.setCenter(recenter);
}

It is a bit of a hack, but I hope someone else finds this useful.