Android permission for android M doesnt work -

here mapsactivity.java file, have used requestpermission callback , yet dialogbox asking me grant location permission doesnt show , app crashes! package saksham.geofencing;

    @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         mgeofences = new arraylist<geofence>();         mgeofencecoordinates = new arraylist<latlng>(); //        double string0=prefencesettings.getstring("latlng0", "34");          setcontentview(r.layout.activity_maps);         showhelpforfirstlaunch();         supportmapfragment supportmapfragment =                 (supportmapfragment) getsupportfragmentmanager().findfragmentbyid(r.id.googlemap);         cd = new connectiondetector(getapplicationcontext());         isinternetpresent = cd.isconnectingtointernet();          // check internet status         if (isinternetpresent) {             // internet connection present             // make http requests                     } else {             // internet connection not present             // ask user connect internet             showalertdialog(mapsactivity.this, "no internet connection",                     "you don't have internet connection.");         }         /**          * supportmapfragment belongs v4 support library, contrary default magfragment native component in android.          supportmapfragment support more android versions, additional library have add in project,          think depends on android versions targeting:          •  on recent versions, default components should enough          •  on older versions need install v4 support library , maybe others          *          */         db = openorcreatedatabase("geofence", context.mode_private, null);         db.execsql("create table if not exists coordinates(id integer,latitude double,longitude double,true varchar);");         db.execsql("insert coordinates values(0,0,0,'0')");         db.execsql("insert coordinates values(1,0,0,'0')");         db.execsql("insert coordinates values(2,0,0,'0')");         googlemap = supportmapfragment.getmap();         log.i("my activity", "maps=" + googlemap);         googlemap.setmylocationenabled(true);         /**          * setmylocationenabled(true/false) shows true location when gps switched on device. inbuilt feature of googlemaps .          */          locationmanager locationmanager = (locationmanager) getsystemservice(service.location_service);         // getting gps status         boolean isgpsenabled = locationmanager.isproviderenabled(locationmanager.gps_provider);         if(!isgpsenabled)         {             utils.displaypromptforenablinggps(this);         }         log.i("my activity", "gps is" + isgpsenabled);          // getting network status         boolean isnetworkenabled = locationmanager                 .isproviderenabled(locationmanager.network_provider);         log.i("my activity", "network is" + isnetworkenabled);          criteria crta = new criteria();         if (build.version.sdk_int > build.version_codes.gingerbread) {             crta.setaccuracy(criteria.accuracy_fine);         } else {             crta.setaccuracy(criteria.accuracy_medium);         }         /**          * have used .setaccuracy fine higher sdks gingerbread .gingerbread used reference because in apks lower          * gingerbread there poor geo-fencing, gingerbread google made lot easier location services used devleopers.          * had improved set of tools location services, included geofencing , substantially improved location discovery.          */         crta.setpowerrequirement(criteria.power_low);         string provider = locationmanager.getbestprovider(crta, true);          /**          * request location updates after every 5 sec or if user traveled 10m          */         log.i("my activity", "manager " + locationmanager);         log.i("my activity", "provider " + provider);         if (build.version.sdk_int >= build.version_codes.m) {             if (activitycompat.checkselfpermission(this, manifest.permission.access_fine_location) != packagemanager.permission_granted && activitycompat.checkselfpermission(this, manifest.permission.access_coarse_location) != packagemanager.permission_granted) {                  mapsactivity.this.requestpermissions(new string[]{manifest.permission.access_fine_location,manifest.permission.write_external_storage,manifest.permission.access_coarse_location}, 100);                  return;             }         }         if (mgoogleapiclient == null) {             mgoogleapiclient = new googleapiclient.builder(this)                     .addconnectioncallbacks((googleapiclient.connectioncallbacks) this)                     .addonconnectionfailedlistener((googleapiclient.onconnectionfailedlistener) this)                     .addapi(locationservices.api)                     .build();             mgoogleapiclient.connect();             log.i("api is", "" + mgoogleapiclient);         }         mlocationrequest = new locationrequest();         // want location update every 10 seconds.         mlocationrequest.setinterval(10000);         // want location accurate possible.         mlocationrequest.setpriority(locationrequest.priority_high_accuracy);           insertgeofence();       }     @override     public void onrequestpermissionsresult(int requestcode, string[] permissions, int[] grantresults) {         switch (requestcode) {             case 100: {                 if (grantresults[0] == packagemanager.permission_granted) {                     toast.maketext(this, "thanks permission", toast.length_long).show();                     // permission granted, yay!                     // calendar task need do.                 } else {                     // permission denied, boo! disable                     // functionality depends on permission.                     toast.maketext(this, "you did not allow access current location", toast.length_long).show();                 }             }             // other 'switch' lines check other             // permissions app might request         }     }       @override     public void onlocationchanged(location location) {         latitude=location.getlatitude();         longitude=location.getlongitude();         cameraposition init =                 new cameraposition.builder()                         .target(new latlng(latitude, longitude))                         .zoom(17.5f)                         .bearing(300f) // orientation                         .tilt(50f) // viewing angle                         .build();         // use googglemap mmap move camera position         googlemap.animatecamera(cameraupdatefactory.newcameraposition(init));     }      @override     public void onconnected(bundle bundle) {         location mlastlocation;         if (build.version.sdk_int >= build.version_codes.m) {             if (checkselfpermission(manifest.permission.access_fine_location) != packagemanager.permission_granted && checkselfpermission(manifest.permission.access_coarse_location) != packagemanager.permission_granted) {                  mapsactivity.this.requestpermissions(new string[]{manifest.permission.access_fine_location,manifest.permission.write_external_storage}, 100);                  return;             }         }         mlastlocation = locationservices.fusedlocationapi.getlastlocation(                 mgoogleapiclient);         startlocationupdates();         if (mlastlocation != null) {             log.i("the last location:", "" + mlastlocation); //            toast.maketext(this, "get last location first asshole!", toast.length_long).show();         }       }       protected void startlocationupdates() {         if (build.version.sdk_int >= build.version_codes.m) {             if (checkselfpermission(manifest.permission.access_fine_location) != packagemanager.permission_granted && checkselfpermission(manifest.permission.access_coarse_location) != packagemanager.permission_granted) {                 mapsactivity.this.requestpermissions(new string[]{manifest.permission.access_fine_location}, 100);                  return;             }             locationrequest mlocationrequest = new locationrequest();              locationservices.fusedlocationapi.requestlocationupdates(                     mgoogleapiclient, mlocationrequest, this);         }     }      } 

you calling googlemap.setmylocationenabled(true) before checking permissions. also, should instantiate location code after check permissions. also, in onrequestpermissionsresult, may want add in location code want initiated.