I have an `Adapter` and a `Sub-Fragment`. I am using an interface to pass data from the `Adapter` to the `Sub-Fragment`. The problem I am having is that I keep getting a `Null Pointer Exception`. I have read through the various posts here relating to the problem and can't figure out where I went wrong. I get the NPE at the line 'passAdapterVariable.passAdapterVariable(mname)'. Based on what I have read I suspect it may be because I am not properly initializing passAdapterVariable. I have tried initializing it several different ways based on other examples but I keep getting the NPE. 

**Here is the Adapter**

```
public class MatchAdapter extends RecyclerView.Adapter<MatchAdapter.MatchViewHolder> {

    //declaration of variables
    private Fragment fragment;
    private FragmentManager fragmentManager;
    private DiscoverPage discoverPage;
    private Context context;
    private int size;
    private int mposition;
    private TextView txt_matchname;
    private ImageView img_matchpic;
    List<String> maImg = new ArrayList<>();
    private String mname;
    PassAdapterVariable passAdapterVariable;

    public interface PassAdapterVariable {

        void passAdapterVariable(String mname);
    }

    //the constructor
    public MatchAdapter(List<String> maImg, int size, Context context, DiscoverPage discoverPage){//, PassAdapterVariable passAdapterVariable) {

        this.maImg = maImg;
        this.context = context;
        this.discoverPage = discoverPage;
        this.size = size;
        //this.passAdapterVariable = (PassAdapterVariable)context;
    }

    public MatchAdapter(String mname, Context context) {
        this.context = context;
        this.passAdapterVariable  = (PassAdapterVariable)context;
    }

    //PassAdapterVariable passAdapterVariable = (PassAdapterVariable) context;

    @Override
    public MatchAdapter.MatchViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.match_items, parent, false);
        MatchViewHolder matchViewHolder = new MatchViewHolder(view, maImg, discoverPage);

        return matchViewHolder;
    }

    @Override
    public void onBindViewHolder(MatchViewHolder holder, int position) {

        Picasso.with(context).load(maImg.get(position)).into(holder.img_match);
        holder.setIsRecyclable(false);

    }

    @Override
    public int getItemCount() {
        return maImg.size();
    }

    //viewholder class
    public class MatchViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

        private static final String TAG = "error";
        //declare variables
        private DiscoverPage discoverPage;
        private ImageView img_match;

        //ViewHolder constructor
        public MatchViewHolder(View itemView, final List<String> maImg, final DiscoverPage discoverPage) {
            super(itemView);

            //initialize variables inside the viewholder constructor
            this.discoverPage = discoverPage;
            img_match = (ImageView) itemView.findViewById(R.id.img_match);
            txt_matchname = (TextView) itemView.findViewById(R.id.txt_matchname);
            img_matchpic = (ImageView) itemView.findViewById(R.id.img_matchpic);

            //set click listener for the img_match
            img_match.setOnClickListener(this);

        }

        @Override
        public void onClick(View view) {
            if (view == img_match) {
                //discoverPage.isHidden();
                Fragment currentFragment;
                fragment = new ClickedMatch();
                fragmentManager = ((AppCompatActivity) context).getSupportFragmentManager();
                FragmentTransaction transaction = fragmentManager.beginTransaction();
                transaction.replace(android.R.id.content, fragment);
                transaction.addToBackStack("DiscoverPage");

                if ((currentFragment = ((AppCompatActivity) context).getSupportFragmentManager().findFragmentById(R.id.main_container)) != null) {
                    transaction.hide(currentFragment);
                }
                else {
                    transaction.commit();
                }

                mname = maImg.get(getAdapterPosition());
                mposition = getAdapterPosition();
                mname = maImg.get(mposition);
                passAdapterVariable.passAdapterVariable(mname);

            }

        }
    }
}

```

**Here is the Sub-Fragment**

```
public class ClickedMatch extends Fragment implements MatchAdapter.PassAdapterVariable{

    //declare variables
    private Toolbar toolbar;
    private TextView txt_matchname;
    private TextView txt_matchprice;
    private ImageView img_matchpic;
    private String mname;
    private String imgmatch;
    List<String> maImg = new ArrayList<>();
    int size;
    Context context;
    DiscoverPage discoverPage;
    private String pname;
    private int i;
    MatchAdapter.PassAdapterVariable passAdapterVariable;

    public ClickedMatch() {
        // Required empty public constructor

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_clicked_match, container, false);

        //initialize variables
        toolbar = (Toolbar) view.findViewById(R.id.toolbar);
        ((AppCompatActivity)getActivity()).setSupportActionBar(toolbar);//set toolbar as action bar
        txt_matchname = (TextView)view.findViewById(R.id.txt_matchname);
        img_matchpic = (ImageView)view.findViewById(R.id.img_matchpic);

        //setHasOptionsMenu(true);

        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getActivity().onBackPressed();
            }
        });

        if(((AppCompatActivity)getActivity()).getSupportActionBar()!= null){
            ((AppCompatActivity) getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            ((AppCompatActivity)getActivity()).getSupportActionBar().setDisplayShowHomeEnabled(true);
            ((AppCompatActivity)getActivity()).getSupportActionBar().setHomeButtonEnabled(true);
            ((AppCompatActivity)getActivity()).getSupportActionBar().setTitle("");
        }

       // MatchAdapter matAdapter = new MatchAdapter(maImg, size, context, discoverPage,
        //passAdapterVariable);

       // matAdapter.passAdapterVariable = this;
        //passAdapterVariable.passAdapterVariable(mname);
        //txt_matchname.setText(pname);

        MatchAdapter matAdapter = new MatchAdapter(pname, getContext());
        matAdapter.passAdapterVariable = this;
        passAdapterVariable(pname);
        txt_matchname.setText(pname);

        return view;
    }
    @Override
    public void passAdapterVariable(String mname) {
       this.pname = mname;

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            this.getActivity().finish();
        }

       return super.onOptionsItemSelected(item);

    }

}

```

**Here is the error log**

```
08-13 21:53:49.341 12852-12852/com.test.jack E/AndroidRuntime: FATAL EXCEPTION: main
     Process: com.test.jack, PID: 12852

     java.lang.NullPointerException: Attempt to invoke interface method 'void com.test.jack.MatchAdapter$PassAdapterVariable.passAdapterVariable(java.lang.String)' on a null object reference
     at com.test.jack.MatchAdapter$MatchViewHolder.onClick(MatchAdapter.java:138)
     at android.view.View.performClick(View.java:5637)
     at android.view.View$PerformClick.run(View.java:22429)
     at android.os.Handler.handleCallback(Handler.java:751)
     at android.os.Handler.dispatchMessage(Handler.java:95)
     at android.os.Looper.loop(Looper.java:154)
     at android.app.ActivityThread.main(ActivityThread.java:6119)
     at java.lang.reflect.Method.invoke(Native Method)
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

```

To add some more context, I have a main activity(UserMainPage). A bottom navigation menu selector replaces the UserMainPage with a fragment(DiscoverPage).

DiscoverPage calls the adapter(MatchAdapter). A button click on DiscoverPage replaces DiscoverPage with a sub-fragment(ClickedMatch).

I am trying to pass a variable from MatchAdapter to ClickedMatch.