onMapReady not being called: Google Map in FrgmentActivity: Android Studio -

i have fragmentactivity in trying load google map. , implements onmapreadycallback , when try inflate map mapfragment object app crashes after getmapasync called. below code:

public class mapactivity extends fragmentactivity implements onmapreadycallback {      private googlemap googlemap;      @override     protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);      setcontentview(r.layout.activity_map);      initializemap();     }      private void initializemap() {         if (googlemap == null) {             supportmapfragment mapfragment = (supportmapfragment) getsupportfragmentmanager()             .findfragmentbyid(r.id.map);             if(mapfragment!=null){                 mapfragment.getmapasync(mapactivity.this);             }              // check if map created or not             if (null== googlemap) {                 toast.maketext(getapplicationcontext(), "sorry! unable create maps", toast.length_short).show();             }         }     }      @override     public void onmapready(googlemap map) {         googlemap = map;         googlemap.setmylocationenabled(true);     } } 

i tried degug , noticed getting mapfragment object never reaches onmapready method makes googlemap object null , app crashes when method pertaining googlemap(e.g. setoncamerachangelistener) being called. have gone through documentation page doesn't seem work in project.

is there might missing in project? how should overcome error , stop app crash.

tia

edit 1:

below map fragment in xml file

<fragment   android:id="@+id/map"   class="com.google.android.gms.maps.supportmapfragment"   android:layout_width="match_parent"   android:layout_height="match_parent"   tools:context=".mapsactivity"   android:name="com.google.android.gms.maps.supportmapfragment"/> 

the hint getmapasync (asynchronous).

onmapready not called straight away, meaning googlemap won't set until method called.

edit: make sure aren't doing methods call on googlemap before set map value, i.e. add check if null before running method on it. add @nullable annotation private googlemap googlemap; aid in development android studio alert if missing null check.