当列表足够滚动时，Recycler View适配器无法正常工作

Question

I have a recycler view adapter like the code I provided. Everything works fine with the action bar delete function until the list is big enough to scroll.

When the list is big selecting multiple items and tapping delete is not deleting the exact selected items. Its deleting some other items. But like always after deleting when the list is doesn't need scroll no more its deleting exact selected items.

So what am I doing wrong here?

package com.itsred1.a1wallet;

import android.content.Context;
import android.graphics.Color;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.view.ActionMode;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.ArrayList;

public class RVDirLisAda extends RecyclerView.Adapter<RVDirLisAda.MyViewHolder> {
    private final Context m_con;
    private final LayoutInflater lay_inf;
    private final ArrayList<RVDat> arr_lis_his_dat;
    private ArrayList<Integer> sel_pos_lis = new ArrayList<>();
    private boolean mul_sel;

   RVDirLisAda(Context context, ArrayList<RVDat> his_dat_arr_lis) {
        m_con = context;
        lay_inf = LayoutInflater.from(context);
        this.arr_lis_his_dat = his_dat_arr_lis;
    }

    private ActionMode.Callback act_mod_cal_bac = new ActionMode.Callback() {

        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            mul_sel = true;
            menu.add("Delete");
            return true;
        }

        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            return false;
        }

        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            for (int pos : sel_pos_lis) {
                arr_lis_his_dat.remove(pos);
            }
            mode.finish();
            return true;
        }

        @Override
        public void onDestroyActionMode(ActionMode mode) {
            mul_sel = false;
            sel_pos_lis.clear();
            notifyDataSetChanged();
        }
    };

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View vie = lay_inf.inflate(R.layout.rv_dir_lis, parent, false);
        return new MyViewHolder(vie);
    }

    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder holder, int position) {
        holder.ini_row(position);
    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {
        private final TextView tv_fil_nam;

        MyViewHolder(View itemView) {
            super(itemView);
            tv_fil_nam = itemView.findViewById(R.id.tv_fil_nam);
        }

        void ini_row(final int pos){
            if (sel_pos_lis.contains(pos)){
                tv_fil_nam.setBackgroundColor(Color.LTGRAY);
            } else {
                tv_fil_nam.setBackgroundColor(Color.WHITE);
            }

            final String fil_nam = arr_lis_his_dat.get(pos).get_row1_col2();
            final String tra_typ = arr_lis_his_dat.get(pos).get_tra_typ();
            final String id = arr_lis_his_dat.get(pos).get_row2_col1();
            tv_fil_nam.setText(fil_nam);
            if(tra_typ.equals("folder")) {
                tv_fil_nam.setCompoundDrawablesWithIntrinsicBounds(R.drawable.ico_fol, 0, 0, 0);
            } else if (tra_typ.equals("file")) {
                tv_fil_nam.setCompoundDrawablesWithIntrinsicBounds(R.drawable.ico_db,0,0,0);
            }

            tv_fil_nam.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    if(!mul_sel){
                        ((AppCompatActivity) v.getContext()).startSupportActionMode(act_mod_cal_bac);
                    }
                    sel_row(pos);
                    return true;
                }
            });

           tv_fil_nam.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(mul_sel){
                        sel_row(pos);
                    } else {
                        cal_bac(id, fil_nam, pos);
                    }
                }
            });
        }

        void sel_row(int pos) {
            if (mul_sel) {
                if (sel_pos_lis.contains(pos)) {
                    int i = sel_pos_lis.lastIndexOf(pos);
                    sel_pos_lis.remove(i);
                    tv_fil_nam.setBackgroundColor(Color.WHITE);
                } else {
                    sel_pos_lis.add(pos);
                    tv_fil_nam.setBackgroundColor(Color.LTGRAY);
                }
            }
        }

        void cal_bac(String id, String tra_typ, int pos) {
            CalBacCom cal_bac_com = null;
            if (m_con instanceof CalBacCom) {
                cal_bac_com = (CalBacCom) m_con;
            }

            if (cal_bac_com != null) {
                cal_bac_com.ini_cal_bac (id, tra_typ, pos, "row_cli");
            }
        }

    }
}

Answer 1

Inside your OnClickListener s you are referencing a position value that could change very quickly as you scroll up or down. This happens because your view holder is re-used to inflate new items that become visible thus avoiding new memory allocation, in the other words, the adapter takes the view holder from items that become "hidden" and reuse them on items that become "visible" while you scroll. Instead use the getAdapterPosition method inside those listeners. For example, instead of doing this...

tv_fil_nam.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mul_sel){
                    sel_row(pos);
                } else {
                    cal_bac(id, fil_nam, pos);
                }
            }
        });

do this...

tv_fil_nam.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mul_sel){
                    sel_row(getAdapterPosition());
                } else {
                    cal_bac(id, fil_nam, getAdapterPosition());
                }
            }
        });

Answer 2

for (int pos : sel_pos_lis) {
    arr_lis_his_dat.remove(pos);
}

This part of your code has an issue, when you remove some item at some position then the position of next items will change and other remove actions could fail and remove some other items. You should remove options with a higher index first but it's not related to scrolling and big lists.