android - why my MotionEvent.ACTION_BUTTON_PRESS did not call -

i have problem 1 of feature ontouchlistener. here code.

private float mprevx; private float mprevy; private static final string tag = "moveablebutton"; public mainactivity mainactivity; public moveablebutton(mainactivity mainactivity1) {     mainactivity=mainactivity1; }  @override public boolean ontouch(view view, motionevent motionevent) {      float currx,curry;      if (motionevent.getactionmasked()==motionevent.action_button_press)     {          log.d(tag, "ontouch: action_button_press");         intent = new intent(mainactivity, newactivity.class);         mainactivity.startactivity(i);         return true;     }      else if(motionevent.getactionmasked()==motionevent.action_down)     {          log.d(tag, "ontouch:action_down ");         mprevx = motionevent.getx();         mprevy = motionevent.gety();         return true;     }      else if (motionevent.getactionmasked()==motionevent.action_move)     {          log.d(tag, "ontouch: action_move");         currx = motionevent.getrawx();         curry = motionevent.getrawy();         viewgroup.marginlayoutparams marginparams = new viewgroup.marginlayoutparams(view.getlayoutparams());         marginparams.setmargins((int)(currx - mprevx), (int)(curry - mprevy),0, 0);         android.support.design.widget.coordinatorlayout.layoutparams layoutparams = new android.support.design.widget.coordinatorlayout.layoutparams(marginparams);         view.setlayoutparams(layoutparams);         return true;     }      return false; } 

as can see want move button anywhere on screen(it works fine) wan when press button new activity called. motionevent.action_button_press never call. i have grid view 3 column in activity sorry poor english , in advance.

and in main activity

 button fab = (button) findviewbyid(r.id.fab);     moveablebutton buttonmove = new moveablebutton(this);      fab.setontouchlistener(buttonmove);