如何永久删除列表视图项？

Question

I have this code, where the listview item gets deleted from the list, but after I reload the listview, the item re-appears again. How do I delete the item permanently? Please help me.

The code for deleting the listview item :

 b2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                 checkedItemPositions = listView.getCheckedItemPositions();
                int itemCount = listView.getCount();

                for(int i=itemCount-1; i >= 0; i--){
                    if(checkedItemPositions.get(i)){
                        str=list.get(i);
                        adapter.remove(str);
                    }
                }
                checkedItemPositions.clear();
                adapter.notifyDataSetChanged();
                listView.setAdapter(adapter);

            }
        });

Edit: As asked by @Nirup Iyer, this is my complete code:

   package com.example.myapplication;

import android.app.PendingIntent;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.Snackbar;
import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Collections;
import java.util.List;

import static com.example.myapplication.Pop_up.s2;
import static com.example.myapplication.Pop_up.text1;
import static com.example.myapplication.Pop_up.thedate;
import static com.example.myapplication.Pop_up_2.aManager;
import static com.example.myapplication.Pop_up_2.dat;
import static com.example.myapplication.Pop_up_2.dite;
import static com.example.myapplication.Pop_up_2.pIntent;
import static com.example.myapplication.Pop_up_2.pqr;
import static com.example.myapplication.Pop_up_2.s;
import static com.example.myapplication.modify_events.st;
import static com.example.myapplication.modify_events_1.st1;
import static com.example.myapplication.modify_events_2.st2;

public class modify_events_3 extends nav_draw {
    ListView listView;
    TextView textView;
    ArrayAdapter<String> adapter;
    String day,month,year;
    Button b1,b2;
    String str=null;
    List<String> list = new ArrayList<String>();
    SparseBooleanArray checkedItemPositions;
    int i,j;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.events_week);
        listView = (ListView) findViewById(R.id.listView);
        textView = (TextView) findViewById(R.id.textView);
        b1=(Button)findViewById(R.id.button10);
        b2=(Button)findViewById(R.id.button11);
        final String arr[]=new String[10];
        if(dite==null)
        {
            startActivity(new Intent(modify_events_3.this,nav_draw.class));
            Toast.makeText(getApplicationContext(),"Please create an event first", Toast.LENGTH_SHORT).show();
        }else {
               DateFormat format2 = new SimpleDateFormat("EEE");
            DateFormat format3 = new SimpleDateFormat("MMM");
            DateFormat format4 = new SimpleDateFormat("yyyy");
            day = format2.format(dite);
             month = format3.format(dite);
             year = format4.format(dite);
            list.add(pqr);
            adapter = new ArrayAdapter<String>(modify_events_3.this, android.R.layout.simple_list_item_multiple_choice, list);
            //Toast.makeText(getApplicationContext(), day + "" + month + "" + year, Toast.LENGTH_LONG).show();
        }
        if (((st2.equals(day)) && (st1.equals(month)) && (st.equals(year)))) {
            listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
            listView.setAdapter(adapter);
            b1.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    SparseBooleanArray checked = listView.getCheckedItemPositions();
                    ArrayList<String> selectedItems = new ArrayList<String>();
                    for(int i=0;i<checked.size();i++) {
                        int position;
                        position = checked.keyAt(i);
                        if (checked.valueAt(i))
                            selectedItems.add(adapter.getItem(position));
                        for (int j = 0; j < arr.length; j++) {
                            str = listView.getItemAtPosition(i).toString();
                            str = arr[j];
                        }
                    }
                        startActivity(new Intent(modify_events_3.this,Pop_up.class));
                    Intent incoming = getIntent();
                    String dat = incoming.getStringExtra("date");
                        thedate.setText(dat);
                        text1.setText(str);
                        Toast.makeText(getApplicationContext(), "Have anything else in mind? ;)", Toast.LENGTH_SHORT).show();
                }
            });
            b2.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                     checkedItemPositions = listView.getCheckedItemPositions();
                    int itemCount = listView.getCount();

                    for(int i=itemCount-1; i >= 0; i--){
                        if(checkedItemPositions.get(i)){
                            str=list.get(i);
                            adapter.remove(str);
                        }
                    }
                    checkedItemPositions.clear();
                    adapter.notifyDataSetChanged();
                    adapter=null;
                    listView.setAdapter(adapter);
                    aManager.cancel(pIntent);
                    Toast.makeText(getApplicationContext(), "The alarm has been deleted successfully", Toast.LENGTH_SHORT).show();
                    startActivity(new Intent(modify_events_3.this,nav_draw.class));
                }
            });
        } else {
            adapter=null;
            listView.setAdapter(adapter);
            Snackbar snackbar = Snackbar.make(findViewById(android.R.id.content), "No event was created", Snackbar.LENGTH_LONG);
            snackbar.show();
        }
    }
}

Do I have to write the item in a file?

Answer 1

From what you have said and from seeing the code, the item will reappear on the list. This is because, when you reload the activity, the onCreate() method is called again, and the entire code in the onCreate() is executed. That means your list is created again, the adapter is initialized again and the listview is populated again. Any changes you make to the list will last until the activity remains active.

If you want the deleted item to be deleted even after the activity dies, you can write your list item into a persistent storage (Database, SharedPreferences or internal/external storage)(More details here ). This way, any modifications you make can be saved in the storage and read back from there in the onCreate method.