How to go other Tabs by clicking on a Button from the current Tab in Android?

You have to call parent view inside your fragment.

public class MoviesFragment extends Fragment {

     ViewPager viewPager;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_movies, container, false);

        Button btn = (Button) rootView.findViewById(R.id.btn);
        viewPager = (ViewPager) getActivity().findViewById(R.id.pager);

           btn.setOnClickListener(new View.OnClickListener() 
           {

               @Override
              public void onClick(View v) 
              {
                   viewPager.setCurrentItem(0);


              }
          }); 

        return rootView;
    }

}

your ViewPager is null because you are not initializing the variable.

You need do

public class MoviesFragment extends Fragment {

ViewPager viewPager;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle    savedInstanceState) 
{

   View rootView = inflater.inflate(R.layout.fragment_movies, container, false);

   Button btn = (Button) rootView.findViewById(R.id.btn);
   viewPager = (ViewPager) rootView.findViewById(R.id.some_viewpager);//Initializing
   btn.setOnClickListener(new View.OnClickListener() 
   {

       @Override
      public void onClick(View v) 
      {

          viewPager.setCurrentItem(0);

      }
  }); 


 return rootView;
}}