How to build an AlertDialog with reflection?

i can't build an AlertDialog with reflection, Please help me

the my code:

try {
    Class dlg= AlertDialog.Builder.class;
    Method m=dlg.getDeclaredMethod("show",Context.class);
    m.invoke(dlg.newInstance(),this);
} catch (Exception e) {
   Log.e("Error!",e.getMessage());
}

error outputed: E/Error!: show [class android.content.Context]