RecyclerView 中的定位是如何工作的？

Question

So I have a little problem where I have a giant recycler view (7000 items) and I have it filled up with generated cards that have college information on them and a button on the right hand side. I included a picture for you to see exactly what I mean. So here is the question: I want to fetch the name and ID when I click on the "details" button so that I can query the rest of college information from an SQLite database later but when I scroll down enough and click the button it sometimes returns information of other college instead of the one I want. The first one always works as intended though. Here is the adapter code:

public class CustomRecyclerAdapter extends RecyclerView.Adapter<CustomRecyclerAdapter.CustomViewHolder> implements Filterable {

    private List<CollegeItem> collegeList;
    private List<CollegeItem> collegeListFull;
    private ItemClickListener itemClickListener;
    private Context context;
    private Button details;
    private DatabaseCollege collegeDB;

    public CustomRecyclerAdapter(List<CollegeItem> collegeList, Context context) {
        this.collegeList = collegeList;
        this.context = context;
        collegeListFull = new ArrayList<>(collegeList);
    }

    @NonNull
    @Override
    public CustomRecyclerAdapter.CustomViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(context).inflate(R.layout.college_item, parent, false);
        return new CustomRecyclerAdapter.CustomViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(CustomRecyclerAdapter.CustomViewHolder holder, int position) {
        final String id = collegeList.get(position).getId();
        final String name = collegeList.get(position).getName();
        holder.name.setText(collegeList.get(position).getName());
        holder.id.setText(collegeList.get(position).getId());
        details.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                System.out.println(id + " - " + name); //This sometimes gives information of incorrect college when clicked
            }
        });
    }

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

    public void setItemClickListener(ItemClickListener itemClickListener) {
        this.itemClickListener = itemClickListener;
    }

    @Override
    public Filter getFilter() {
        return collegeFilter;
    }

    public Filter getFilterName() {
        return collegeFilterName;
    }

    private Filter collegeFilter = new Filter() {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            List<CollegeItem> filteredList = new ArrayList<>();

            if(constraint == null || constraint.length() == 0) {
                filteredList.addAll(collegeListFull);
            } else {
                String filterPattern = constraint.toString().toLowerCase().trim();

                for(CollegeItem college : collegeListFull) {
                    if(college.getName().toLowerCase().contains(filterPattern)) {
                        filteredList.add(college);
                    }
                }
            }
            FilterResults results = new FilterResults();
            results.values = filteredList;
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            collegeList.clear();
            collegeList.addAll((List) results.values);
            notifyDataSetChanged();
        }
    };

    private Filter collegeFilterName = new Filter() {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            List<CollegeItem> filteredList = new ArrayList<>();

            if(constraint == null || constraint.length() == 0) {
                filteredList.addAll(collegeListFull);
            } else {
                String filterPattern = constraint.toString().toLowerCase().trim();

                for(CollegeItem college : collegeListFull) {
                    if(college.getId().toLowerCase().contains(filterPattern)) {
                        filteredList.add(college);
                    }
                }
            }
            FilterResults results = new FilterResults();
            results.values = filteredList;
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            collegeList.clear();
            collegeList.addAll((List) results.values);
            notifyDataSetChanged();
        }
    };

    public class CustomViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView name, id;

        public CustomViewHolder(View v) {
            super(v);
            name = v.findViewById(R.id.college_name);
            id = v.findViewById(R.id.college_id);
            details = v.findViewById(R.id.btn_college_details);
        }

        @Override
        public void onClick(View v) {
            if(itemClickListener != null) {
                itemClickListener.onClick(v, getAdapterPosition());
            }
        }
    }
}

I am not sure exactly why but it seems to be a positioning issue maybe? Because when I scroll and click the information outputed seem to change. Whats the correct way to get the information from the cards the way I want?

and just in case here is the fragment java code where the recycler view sits:

public class CollegeFragment extends Fragment implements ItemClickListener{

    private RecyclerView recyclerView;
    private CustomRecyclerAdapter customRecyclerAdapter;
    private List<CollegeItem> collegeItemList = new ArrayList<>();
    private DatabaseCollege dbCollege;
    private EditText cName, cId;


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

        dbCollege = new DatabaseCollege(getActivity());

        recyclerView = myFragmentView.findViewById(R.id.recycler);
        customRecyclerAdapter = new CustomRecyclerAdapter(dbCollege.getCollegeData(), getActivity());

        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setAdapter(customRecyclerAdapter);
        customRecyclerAdapter.setItemClickListener(this);

        cId = myFragmentView.findViewById(R.id.et_ipeds);
        cId.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                cName.getText().clear();
                CollegeFragment.this.customRecyclerAdapter.getFilter().filter(s);
            }

            @Override
            public void afterTextChanged(Editable s) {
            }
        });

        cName = myFragmentView.findViewById(R.id.et_name);
        cName.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {

            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                cId.getText().clear();
                CollegeFragment.this.customRecyclerAdapter.getFilterName().filter(s);
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });
        return myFragmentView;

    }

    @Override
    public void onClick(View v, int position) {
        String name = collegeItemList.get(position).getName();
        String id = collegeItemList.get(position).getId();
    }
}

Answer 1

Adapter

public class CustomRecyclerAdapter extends RecyclerView.Adapter<CustomRecyclerAdapter.CustomViewHolder> implements Filterable {

    private List<CollegeItem> collegeList;
    private List<CollegeItem> collegeListFull;
    private ItemClickListener itemClickListener;
    private Context context;
    private DatabaseCollege collegeDB;

    public CustomRecyclerAdapter(List<CollegeItem> collegeList, Context context) {
        this.collegeList = collegeList;
        this.context = context;
        collegeListFull = new ArrayList<>(collegeList);
    }

    @NonNull
    @Override
    public CustomRecyclerAdapter.CustomViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(context).inflate(R.layout.college_item, parent, false);
        return new CustomRecyclerAdapter.CustomViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(CustomRecyclerAdapter.CustomViewHolder holder, int position) {
        final String id = collegeList.get(position).getId();
        final String name = collegeList.get(position).getName();
        holder.name.setText(collegeList.get(position).getName());
        holder.id.setText(collegeList.get(position).getId());
    }

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

    public void setItemClickListener(ItemClickListener itemClickListener) {
        this.itemClickListener = itemClickListener;
    }

    @Override
    public Filter getFilter() {
        return collegeFilter;
    }

    public Filter getFilterName() {
        return collegeFilterName;
    }

    private Filter collegeFilter = new Filter() {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            List<CollegeItem> filteredList = new ArrayList<>();

            if(constraint == null || constraint.length() == 0) {
                filteredList.addAll(collegeListFull);
            } else {
                String filterPattern = constraint.toString().toLowerCase().trim();

                for(CollegeItem college : collegeListFull) {
                    if(college.getName().toLowerCase().contains(filterPattern)) {
                        filteredList.add(college);
                    }
                }
            }
            FilterResults results = new FilterResults();
            results.values = filteredList;
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            collegeList.clear();
            collegeList.addAll((List) results.values);
            notifyDataSetChanged();
        }
    };

    private Filter collegeFilterName = new Filter() {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            List<CollegeItem> filteredList = new ArrayList<>();

            if(constraint == null || constraint.length() == 0) {
                filteredList.addAll(collegeListFull);
            } else {
                String filterPattern = constraint.toString().toLowerCase().trim();

                for(CollegeItem college : collegeListFull) {
                    if(college.getId().toLowerCase().contains(filterPattern)) {
                        filteredList.add(college);
                    }
                }
            }
            FilterResults results = new FilterResults();
            results.values = filteredList;
            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            collegeList.clear();
            collegeList.addAll((List) results.values);
            notifyDataSetChanged();
        }
    };

    public class CustomViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView name, id;
        Button details; // Button should be here

        public CustomViewHolder(View v) {
            super(v);
            name = v.findViewById(R.id.college_name);
            id = v.findViewById(R.id.college_id);
            details = v.findViewById(R.id.btn_college_details);

            details.setOnClickListener(this); // set click listener here instead
        }

        @Override
        public void onClick(View v) {
            if(itemClickListener != null) {
                itemClickListener.onClick(v, getAdapterPosition());
            }
        }
    }
}

Here, you're utilizing the ItemClickListener callback that you implemented in your fragment instead of creating new instances of click listener for your details button. In this case, your listener for all items is your Fragment that implements ItemClickListener