Want to subscribe to 'map loading finished' event or similar

I am facing an issue while displaying my custom objects on map. There are two types on objects, viz. tt.marker and Geojson lines. When the objects are prepared and added to map at the time the map is being displayed for first time, the Geojson objects are not shown. Sometime they are shown and then vanish. As I suspected, the issue was due to the order of execution. If the map loading finishes after the objects are added, the Geojson objects are not shown. As a workaround, I am having two buttons, one that shows the map and second to load the objects. In this method, all the objects are shown properly. But this is work around. To implement properly, I need to start loading the objects when the map loading is finished. Please share sample code to subscribe to “map loading completed” event or something like that.