Swipe to delete Recyclerview brings about a null object reference error

Question

I am working with a recyclerview and am implementing swipe to delete. the code works pretty well but when I try getting my list from the adapter so that I implement swipe to delete, I get a null object reference. My adapter class is below

public class TlAdapter extends RecyclerView.Adapter<TimelineVholder> {
private List<FetchModel> models;
private Context context;


public TlAdapter(List<FetchModel> models,Context context) {
    this.models = models;
    this.context= context;
}

@NonNull
@Override
public TimelineVholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view= LayoutInflater.from(context).inflate(R.layout.timeline,parent,false);

   return new TimelineVholder(view,viewType);
}

@Override
public void onBindViewHolder(@NonNull TimelineVholder holder, final int position) {
    SharedPreferences preferences= PreferenceManager.getDefaultSharedPreferences(context);
    final SharedPreferences.Editor editor=preferences.edit();

        FetchModel list= models.get(position);

        String activity= list.getJournalEntry();
        String time= list.getTime();

        holder.activity.setText(activity);
        holder.time.setText(time);
 }

@Override
public int getItemViewType(int position) {
    return TimelineView.getTimeLineViewType(position,getItemCount());
}
@Override
public int getItemCount() {

    int arr=0;
    try {
        if (models.size()==0){
            arr=0;
        }
        else {
            arr=models.size();
        }
    }
    catch (Exception e){}
    return arr;
}

public List<FetchModel> getkey(){
    return models;
}

}

and my recyclerview gesture class is as below

public class RecyclerViewBasic  {
private Context context;
private List<FetchModel> modelList;
public RecyclerViewBasic(Context context) {
    this.context = context;
}
public void recyclerGesture(){
    new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0,
            ItemTouchHelper.RIGHT|ItemTouchHelper.LEFT) {
        @Override
        public boolean onMove(RecyclerView recyclerView, 
RecyclerView.ViewHolder
                viewHolder, RecyclerView.ViewHolder target) {
            return false;
        }

        @Override
        public void onSwiped(RecyclerView.ViewHolder viewHolder, int 
direction) {
            int position= viewHolder.getAdapterPosition();

            TlAdapter adapter= new TlAdapter(modelList,context);

            modelList= adapter.getkey();
            modelList.remove(position);
            adapter.notifyDataSetChanged();

        }
    }).attachToRecyclerView(recyclerView);

}

and the error in my logcat is as below also

06-29 13:19:41.691 4282-4282/com.revosleap.journal E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.revosleap.journal, PID: 4282
java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object java.util.List.remove(int)' on a null object reference
    at com.revosleap.journal.RecyclerUtils.RecyclerView.RecyclerViewBasic$2.onSwiped(RecyclerViewBasic.java:89)
    at android.support.v7.widget.helper.ItemTouchHelper$4.run(ItemTouchHelper.java:692)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:145)
    at android.app.ActivityThread.main(ActivityThread.java:5942)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

I have gone through a number of similar questions here and tried the methods suggested but I cannot get the one that helps me out. I even tried to populate the list anew but it even got me another error. I'd really appreciate any possible help. Thanks.

This is not complete logs. There will be a line with message "Caused by..." — Gokul Nath KP, Jun 29 '18 at 10:28

score 1 · Answer 1 · answered Jun 29 '18 at 10:25

1

You have not initialized modelList. So accept one more parameter in the constructor of RecyclerViewBasic and initialize the list.

answered Jun 29 '18 at 10:25

Abdul Wadood

1,161
1
10
18

I have done it and the error still persists. – Carlos Anyona Jun 29 '18 at 10:35
So every time `onSwiped` is called a new object of adapter is being created which should not be the case. There should only be one object of the adapter. – Abdul Wadood Jun 29 '18 at 10:38
You can create the object of the adapter where you are binding the adapter with the recycler view and pass that object to the constructor of RecyclerViewBasic as another parameter. – Abdul Wadood Jun 29 '18 at 10:43

Swipe to delete Recyclerview brings about a null object reference error

1 Answers1