Android: Starting ActionMode inside ViewPager's Fragment -

i working on app have viewpager 3 fragments in using tablayout. trying start actionmode recycler view select multiple views on longclick. below code

actionmode = ((appcompatactivity)getactivity()).startsupportactionmode(actionmodecallback); 

but give me error

java.lang.nullpointerexception: attempt invoke virtual method 'android.support.v7.view.actionmode android.support.v7.app.appcompatactivity.startsupportactionmode(android.support.v7.view.actionmode$callback)' on null object reference 

i have tried this

mymainactivity activity=(mymainactivity)getactiivty(); activity.startsupportactionmode(actionmodecallback); 

but gaves me same error. highly appreciated. in advance

in actionmode.callbacks:

actionmode.callback actionmodecallbacks = new actionmode.callback() {         @override         public boolean oncreateactionmode(actionmode mode, menu menu) {             return false;         }         ///     }; 

change boolean false true:

actionmode.callback actionmodecallbacks = new actionmode.callback() {         @override         public boolean oncreateactionmode(actionmode mode, menu menu) {             return true;         }         ///     };