Attempt to invoke virtual method 'java.util.UUID..' on a null object refrence when using Swip To Dismiss RecyclerView

Question

I'm trying using Swip To Dismiss RecyclerView, i used this tutorial

but when i'm trying to delete item in my FragmentOne by swipeToDelete method, it shows this Error:

    java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.UUID com.drgnme.listhamrah.Detail.getId()' on a null object reference
at com.drgnme.listhamrah.DetailLab.deleteDetail(DetailLab.java:82)
at com.drgnme.listhamrah.FragmentOne$DetailAdapter.swipeToDelete(FragmentOne.java:396)
at com.drgnme.listhamrah.ItemSwipeHelper.onSwiped(ItemSwipeHelper.java:43)
at android.support.v7.widget.helper.ItemTouchHelper$4.run(ItemTouchHelper.java:681)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5451)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

i used this in another place in this Fragment for Delete item and it's work just fine, don't know what's the problem here..

this :

DetailLab.get(getActivity()).deleteDetail(mDetail);
updateUI();
updateNumbers();

and here is my FragmentOne:

public class FragmentOne extends Fragment {
private static final String
        SAVED_NUMBER_VISIBLE = "number";

private RecyclerView mDetailRecyclerView;
private DetailAdapter mAdapter;
private boolean mNumberVisible;

private View view;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setHasOptionsMenu(true);
}


@Override
public View onCreateView(LayoutInflater inflater,
                         ViewGroup container,
                         Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.fragment_one_layout,
            container, false);

    mDetailRecyclerView = (RecyclerView) view.findViewById(R.id.detail_recycler_view);

    LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
    layoutManager.setReverseLayout(true); //This will reverse the data order but not scroll the RecyclerView to the last item
    layoutManager.setStackFromEnd(true); //For keeping data order same and simply scrolling the RecyclerView to the last item
    mDetailRecyclerView.setLayoutManager(layoutManager);

    if (savedInstanceState != null) {
        mNumberVisible =
                savedInstanceState.getBoolean(SAVED_NUMBER_VISIBLE);
    }

    updateUI();


    return view;
}

@Override
public void onResume() {
    super.onResume();
    updateUI();
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBoolean(SAVED_NUMBER_VISIBLE, mNumberVisible);
}
..
..    


protected void updateUI() {
    DetailLab detailLab = DetailLab.get(getActivity());
    List<Detail> details = detailLab.getDetails();
    if (details.size() == 0) {
        LinearLayout linearLayout = (LinearLayout) view.findViewById(R.id.empty_view);
        linearLayout.setVisibility(View.VISIBLE);
    } else {
        LinearLayout linearLayout = (LinearLayout) view.findViewById(R.id.empty_view);
        linearLayout.setVisibility(View.GONE);
    }

    if (mAdapter == null) {
        mAdapter = new DetailAdapter(details);
        mDetailRecyclerView.setAdapter(mAdapter);

    } else {
        mAdapter.setDetails(details);
        mAdapter.notifyDataSetChanged();
    }

    updateNumbers();
}

private class DetailHolder extends RecyclerView.ViewHolder
        implements View.OnClickListener, View.OnLongClickListener {
    private TextView mTitleTextView;
    //        private TextView mDateTextView;
    private Detail mDetail;
    private RatingBar mRatingBar;

    public DetailHolder(LayoutInflater inflater, ViewGroup parent) {
        super(inflater.inflate(R.layout.list_item_detail,
                parent, false));

        itemView.setOnClickListener(this);
        itemView.setOnLongClickListener(this);
        mTitleTextView = (TextView) itemView.findViewById(R.id.detail_title);
        mRatingBar = (RatingBar) itemView.findViewById(R.id.ratingBar);
    }

    public void bind(Detail detail) {
        mDetail = detail;
        mTitleTextView.setText(mDetail.getTitle());
        mRatingBar.setRating(mDetail.getRate());
    }

    @Override
    public void onClick(View view) {
        Intent intent = DetailPagerActivity.newIntent(getActivity(),
                mDetail.getId());
        startActivity(intent);
    }

    @Override
    public boolean onLongClick(View v) {

        AlertDialog.Builder alert = new AlertDialog.Builder(
                getActivity());
        alert.setMessage(R.string.alert);
        alert.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                DetailLab.get(getActivity()).deleteDetail(mDetail);
                updateUI();
                updateNumbers();
                dialog.dismiss();
            }
        });
        alert.setNegativeButton("No", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
            }
        });
        alert.show();
        return true;
    }
}


private class DetailAdapter extends RecyclerView.Adapter<DetailHolder> implements ItemTouchHelperAdapter {
    private List<Detail> mDetails;
    private Detail mDetail;

    public DetailAdapter(List<Detail> details) {
        mDetails = details;
    }

    @Override
    public DetailHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater =
                LayoutInflater.from(getActivity());

        return new DetailHolder(layoutInflater, parent);
    }

    @Override
    public void onBindViewHolder(DetailHolder holder, int position) {
        Detail detail = mDetails.get(position);
        holder.bind(detail);
    }

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

    public void setDetails(final List<Detail> details) {
        mDetails = details;


        ItemTouchHelper.Callback itemTouchCallBack=new ItemSwipeHelper(Direction.RIGHT, mAdapter);
        ItemTouchHelper swipeToDismissTouchHelper =new ItemTouchHelper(itemTouchCallBack);
        swipeToDismissTouchHelper.attachToRecyclerView(mDetailRecyclerView);

    }


    @Override
    public void swipeToDelete(int position) {

    DetailLab.get(getActivity()).deleteDetail(mDetail);
    updateUI();
    updateNumbers();

    }
}
}

Answer 1

The problem wasn't about the Library that i used, i should have give the item's position for delete , so i just added this line in the first of my swipeToDelete method and fix the problem:

 mDetail = mDetails.get(position);