Removing view of recycler view

Question

In my application, i am using a recycler view and a array list as its datasource for the adapter, the problem is after i remove the index from the array list, i don't know how to remove view at that index from recyclerview which results in application crashing sometimes.

Here is the fragment where i am defining and initializing the recycler view .

public class PastClasses extends Fragment{
ArrayList<GetAllPastClasses> Pastclasslist;
View rootView;
Context mcontext;

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

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

        Bundle bn = getArguments();

        Pastclasslist = (ArrayList<GetAllPastClasses>) bn.getSerializable("class_detailss");


        mcontext = PastClasses.this.getActivity();
        rv = (RecyclerView) rootView.findViewById(R.id.rv);

        LinearLayoutManager llm = new LinearLayoutManager(mcontext);
        rv.setLayoutManager(llm);
        rv.setHasFixedSize(true);


        PastClassesAdapter adapter = new PastClassesAdapter(Pastclasslist, mcontext);

        //final Class_Details_PagerAdapter adapter = new Class_Details_PagerAdapter(getSupportFragmentManager(), 2);
        rv.setAdapter(adapter);

    return rootView;
}

And here is the Adapter class. Here in the remove method i am removing the item from list but i don't know how to remove view from the recycler view .

    public class PastClassesAdapter extends RecyclerView.Adapter<PastClassesAdapter.PersonViewHolder> {

private static final String TAG = "CustomAdapter";
String STARTPOINT = "https://www.vario.fitness";
ArrayList<GetAllPastClasses> Pastclasslist;
CancelClass cnclass;
String user_id ="442";
public static class PersonViewHolder extends RecyclerView.ViewHolder {
    CardView cv;
    TextView txt_class_name; //txt_class_name
    TextView txt_bsns_name;
    ImageView img_class;
    ImageView img_rate;
    ImageView img_timer;
    TextView txt_area_name;
    TextView txt_time;

    public PersonViewHolder(View itemView) {
        super(itemView);
        // Define click listener for the ViewHolder's View.


        cv = (CardView) itemView.findViewById(R.id.cvPastClasses);
        txt_class_name = (TextView) itemView.findViewById(R.id.txt_class_name);
        txt_bsns_name = (TextView) itemView.findViewById(R.id.txt_bsns_name);
        img_timer = (ImageView) itemView.findViewById(R.id.img_timer);
        txt_area_name = (TextView) itemView.findViewById(R.id.txt_area_name);
        txt_time = (TextView)itemView.findViewById(R.id.txt_time);
        img_class= (ImageView) itemView.findViewById(R.id.img_class);
        img_rate= (ImageView) itemView.findViewById(R.id.img_rate);
    }

}
Context mcontext;

public PastClassesAdapter (ArrayList<GetAllPastClasses> Pastclasslist , Context mcontext) {
    this.mcontext=mcontext;
    this.Pastclasslist = Pastclasslist;

    //System.out.println("size:  "+Pastclasslist.size());
}

public int getItemCount() {
    return Pastclasslist.size();
}

public void remove(GetAllPastClasses item) {
    int position = Pastclasslist.indexOf(item);
    Pastclasslist.remove(position);
    notifyItemRemoved(position);
}


public PersonViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
    View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.content_main_pastclass, viewGroup, false);
    PersonViewHolder pvh = new PersonViewHolder(v);
    return pvh;
}
// String name, String date, int photoId, String rate, String review

public void onBindViewHolder(final PersonViewHolder personViewHolder, final int i) {

        if (!checkNullity(Pastclasslist.get(i).getClassName())) {

                  personViewHolder.txt_class_name.setText(Pastclasslist.get(i).getClassName());

        } else {
            personViewHolder.txt_class_name.setText("GYM CLASS");
        }
        if (!checkNullity(Pastclasslist.get(i).getArea())) {
            personViewHolder.txt_area_name.setText(Pastclasslist.get(i).getArea());
        }
        if (!checkNullity(Pastclasslist.get(i).getBusinessName())) {
            personViewHolder.txt_bsns_name.setText(Pastclasslist.get(i).getBusinessName());
        }
        if (!checkNullity(Pastclasslist.get(i).getClassDuration()) && !checkNullity(Pastclasslist.get(i).getSchdDate())) {
            personViewHolder.txt_time.setText(Pastclasslist.get(i).getSchdDate().substring(11, 16) + " | " + Pastclasslist.get(i).getClassDuration());
        }
        if (!checkNullity(Pastclasslist.get(i).getPhoto())) {
            //   personViewHolder.Userprofilepic.setImageResource((persons[i].getPhoto()));

            Picasso.with(mcontext).load(Pastclasslist.get(i).getPhoto().replace("\\", "").replaceAll(" ", "%20"))
                    .error(R.mipmap.ic_launcher).into(personViewHolder.img_class);
        } else if (checkNullity(Pastclasslist.get(i).getPhoto())) {
            personViewHolder.img_class.setImageResource(R.mipmap.ic_launcher);

        }

        personViewHolder.img_rate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {


                final AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(mcontext);
                alertDialogBuilder.setTitle("Cancel Class");
                alertDialogBuilder.setMessage("Are you sure,You want to cancel this class");
                alertDialogBuilder.setIcon(R.mipmap.ic_launcher);
                alertDialogBuilder.setPositiveButton("yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface arg0, int arg1) {
                        //Toast.makeText(mcontext, "You clicked yes button", Toast.LENGTH_LONG).show();
                        MainActivity.pLoading.setMessage("Cancelling..");
                        MainActivity.pLoading.show();

                        // POJO class GetAllPastClasses
                        final OkHttpClient client = new OkHttpClient();
                        final HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
                        interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
                        client.interceptors().add(interceptor);

                        Retrofit retrofit = new Retrofit.Builder().baseUrl(STARTPOINT).addConverterFactory(GsonConverterFactory.create())
                                .client(client).build();
                        RestInterface restInterface = retrofit.create(RestInterface.class);
                        System.out.println("i is :  " + i);
                        Call<CancelClass> objInbox = restInterface.cancelThisClass(null, null, null, null, null);
                        try {
                            objInbox = restInterface.cancelThisClass(Pastclasslist.get(i).getResIdPk(),
                                    Pastclasslist.get(i).getClassIdFk(), Pastclasslist.get(i).getSchdIdFk(), Pastclasslist.get(i).getWeekNoSch(),
                                    user_id);

                        } catch (Exception ex) {
                            ex.printStackTrace();
                        }



                        objInbox.enqueue(new Callback<CancelClass>() {
                            @Override
                            public void onResponse(Response<CancelClass> response, Retrofit retrofit) {

                                cnclass = response.body();

                                if (cnclass.getSucc().equals("1")) {
                                    Toast.makeText(mcontext, cnclass.getMsg(), Toast.LENGTH_LONG).show();
                                    // Pastclasslist.get(i).setCanStatus("1");

                                  remove(Pastclasslist.get(i));

                                } else {
                                    Toast.makeText(mcontext, cnclass.getMsg(), Toast.LENGTH_LONG).show();
                                }
                                MainActivity.pLoading.dismiss();
                            }

                            @Override
                            public void onFailure(Throwable t) {
                                Toast.makeText(mcontext, cnclass.getMsg(), Toast.LENGTH_LONG).show();
                            }
                        });

                    }
                });

                alertDialogBuilder.setNegativeButton("No", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    }
                });

                AlertDialog alertDialog = alertDialogBuilder.create();
                alertDialog.show();
            }
        });

    }

public boolean checkNullity(String responseString) {
    if (responseString == null || responseString.equals("") ||   responseString.equals("-1")) {
        return true;
    } else {
        return false;
    }
}

public void onAttachedToRecyclerView(RecyclerView recyclerView) {
    super.onAttachedToRecyclerView(recyclerView);
}


}

Answer 1

当您从用于初始化适配器的arrayList对象中删除该项目时，只需调用：

adapter.notifyDataSetChanged();

Answer 2

I got the answer, I just need to use both the method notifyItemChanged and notifyItemRangeChanged so that the adapter can know that a view is deleted.Now its working fine when I changed my remove method to something below.

public void remove(GetAllPastClasses item) {
    int position = Pastclasslist.indexOf(item);
    Pastclasslist.remove(position);
    notifyItemRemoved(position);
    notifyItemRangeChanged(position,Pastclasslist.size());
}

Answer 3

Modify your getItemCount() and remove() method as follows :

public int getItemCount() {
        return (null != Pastclasslist ? Pastclasslist.size() : 0);
    }

remove() method

public void remove(GetAllPastClasses item) {
  int position = Pastclasslist.indexOf(item);
  if(position!=-1 && position<Pastclasslist.size())
    {
      Pastclasslist.remove(position);
      notifyItemRemoved(position);
      notifyItemRangeChanged(position, getItemCount());
    }
}

notifyItemRangeChanged(position, getItemCount()); - notifies the RecyclerView Adapter that positions of element in adapter has been changed from position(removed element index to end of list), please update it.

if(position!=-1 && position<Pastclasslist.size()) - this condition verifies that position of element is not equal to -1 and position of element should be less than size of total elements in list. hence not causing unwanted crash due to indexes of elements.