在null对象引用上对'android.support.v7.widget.RecyclerView $ LayoutManager'的任何解决方案

Question

I have been trying to solve this problem for last 10 days I was unable to do so . I have used parse sdk for my app I was able to retrieve from parse server but no it crashes with this error.

java.lang.NullPointerException: Attempt to invoke virtual method void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager) on a null object reference at com.example.sabhaysardana.coolDude.ExamWise.onCreateView(ExamWise.java:75)at android.support.v4.app.Fragment.performCreateView(Fragment.java:2087) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1113) at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1295) at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801) at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1643) at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679) at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143) at android.support.v4.view.ViewPager.populate(ViewPager.java:1272) at android.support.v4.view.ViewPager.populate(ViewPager.java:1120) at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1646)

So considering that app is able to println my values from the parse server but it is not showing in the table(rows) ie recyclerView

(My ExamWise Fragment)

public class ExamWise extends Fragment implements RecyclerViewAdapter.ClickListener {

private RecyclerView recyclerView;
private RecyclerViewAdapter adapter;
private LinearLayoutManager layoutManager;
ArrayList<ItemsModel> data = new ArrayList<>();
ProgressDialog dialog;

public ExamWise() {

}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
}

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

    View rootView = inflater.inflate(R.layout.exam_row,container,false);
    rootView = (RecyclerView)rootView.findViewById(R.id.my_recycler_view);

    layoutManager = new LinearLayoutManager(getActivity());
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL);

    recyclerView.setLayoutManager(layoutManager);

   rootView.findViewById(R.id.my_recycler_view);

    recyclerView.setOnScrollListener(new EndlessRecyclerView(layoutManager) {
        @Override
        public void onLoadMire(int current_page) {
            int limit = current_page * 10;
                LoadItems(limit);
        }
    });

    return rootView;
}

@Override
public void onResume() {
    super.onResume();
    recyclerView.setOnScrollListener(new EndlessRecyclerView(layoutManager) {
        @Override
        public void onLoadMire(int current_page) {
            int limit = current_page * 10;
            LoadItems(limit);
        }
    });
    loadData();
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
}

@Override
public void OnItemClick(View view, int position) {
    Intent i = new Intent(getActivity(), ActivityItemView.class);
    ItemsModel model = data.get(position);
    i.putExtra("examName",model.getTitle());
    i.putExtra("examImage",model.getImageFile());
    startActivity(i);
}

private void LoadItems(int limit) {
    ParseQuery<ParseObject> query = ParseQuery.getQuery("examWise");
    query.setLimit(limit);
    dialog = new ProgressDialog(getActivity());
    dialog.setTitle("Loading");
    dialog.setMessage("Please Wait....");
    dialog.show();

    query.findInBackground(new FindCallback<ParseObject>() {
        @Override
        public void done(List<ParseObject> objects, ParseException e) {
            dialog.dismiss();
            if (e == null) {
                for (int a = 0; a < objects.size(); a++) {
                    ParseObject object = objects.get(a);
                    ItemsModel model = new ItemsModel();
                                      model.setImageFile(object.getParseFile("examImage").toString());

                        model.setTitle(object.getString("examName").toString());
                    data.add(model);
                }
                adapter.UpdateData(data);

            } else if (e.getCode() == ParseException.CONNECTION_FAILED) {
                Toast.makeText(getActivity(),"Error "+ e.getMessage(),Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(getActivity(),"No internet connection!" , Toast.LENGTH_LONG).show();
            }

        }
    });
}

public void loadData() {
    ParseQuery<ParseObject> query = ParseQuery.getQuery("examWise");
    query.addAscendingOrder("date");
    dialog = new ProgressDialog(getActivity());
    dialog.setTitle("Loading");
    dialog.setMessage("Please Wait....");
    dialog.show();

    query.findInBackground(new FindCallback<ParseObject>() {
        @Override
        public void done(List<ParseObject> objects, ParseException e) {
            dialog.dismiss();
            if (e == null) {
                for (int a = 0; a < objects.size(); a++) {
                    ParseObject object = objects.get(a);
                    ItemsModel model = new ItemsModel();
                                            model.setImageFile(object.getParseFile("examImage").toString());                       model.setTitle(object.getString("examName").toString());
                    data.add(model);
                }

                adapter = new RecyclerViewAdapter(data, getActivity());
                adapter.setClickListerner(ExamWise.this);
                recyclerView.setAdapter(adapter);
            } else if (e.getCode() == ParseException.CONNECTION_FAILED) {
                Toast.makeText(getActivity(),"No internet connection!" , Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(getActivity(),"Error "+ e.getMessage(),Toast.LENGTH_LONG).show();

            }

        }
    });
}
}

(My RecyclerViewAdapter)

    public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>  {

ClickListener clickListener;
ArrayList<ItemsModel> itemsArray = null;
Context context;

RecyclerViewAdapter(ArrayList<ItemsModel> itemsArray, Context context)      {
    this.itemsArray = itemsArray;
    this.context = context;
}

public void UpdateData(ArrayList<ItemsModel> itemsArray){
    this.itemsArray = itemsArray;
    notifyDataSetChanged();
}

@Override
public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {

       View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.exam_row,viewGroup,false);
    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(RecyclerViewAdapter.ViewHolder viewHolder, int i) {

    viewHolder.Title.setText(itemsArray.get(i).getTitle()); 
Picasso.with(context).load(itemsArray.get(i).getImageFile()).into(viewHolder.imageView);
}

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

public void setClickListerner(ClickListener clickListerner) {
    this.clickListener = clickListerner;
}


     public  class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{

    public TextView Title;
    public ImageView imageView;
    public View view;

    public ViewHolder(View itemView) {
        super(itemView);
        itemView.setOnClickListener(this);
        this.view = itemView;
        Title = (TextView) view.findViewById(R.id.homeTitle);
        imageView = (ImageView) view.findViewById(R.id.homeImage);
    }

    @Override
    public void onClick(View view) {
        if(clickListener != null){
            clickListener.OnItemClick(view, getPosition());
        }
    }
}

public interface  ClickListener{
    public  void  OnItemClick(View view, int position);
}
}

(My ItemsModel)

public class ItemsModel implements Parcelable {

private String title,imageFile;

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}


public String getImageFile() {
    return imageFile;
}

public void setImageFile(String imageFile) {
    this.imageFile = imageFile;
}

public ItemsModel() {

}

protected ItemsModel(Parcel in) {

 String[] array = new String[2];
    in.readStringArray(array);
    title = array[0];
    imageFile = array[1];
}

public static final Creator<ItemsModel> CREATOR = new     Creator<ItemsModel>() {
    @Override
    public ItemsModel createFromParcel(Parcel in) {
        return new ItemsModel(in);
    }

    @Override
    public ItemsModel[] newArray(int size) {
        return new ItemsModel[size];
    }
};

@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel parcel, int i) {
    parcel.writeStringArray(new String[] {this.title,this.imageFile});
}
}

(My exam_row.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"

android:background="@drawable/list_bg"
>

<com.parse.ParseImageView
    android:id="@+id/homeImage"
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:layout_margin="2dp"
    android:src="@drawable/ic_launcher"
    />

<RelativeLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@id/homeImage"
    >
    <TextView
        android:layout_width="match_parent"
        android:layout_height="30dp"
        android:id="@+id/homeTitle"
        android:gravity="start"
        android:textAlignment="gravity"
        android:paddingRight="5dp"
        android:paddingLeft="3dp"
        android:paddingBottom="5dp"
        android:textSize="21sp"
        android:text="abcdefghijklmnopqrstuvwxyz"
        android:textColor="@color/colorBlack"
        android:maxLines="2"
        />

</RelativeLayout>

(My recycler_row)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="match_parent">

<android.support.v7.widget.RecyclerView
    android:id="@+id/my_recycler_view"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:clickable="true"
    android:background="@color/colorGrey" />

Sorry community I have to attach this much amount of the code but my moral is getting down minute by minute . It's my first android project I hope get your result guys.

Answer 1

You are inflating your RecyclerView into another variable Change this

rootView = (RecyclerView)rootView.findViewById(R.id.my_recycler_view);

to this

recyclerView = (RecyclerView)rootView.findViewById(R.id.my_recycler_view);