不能从列表视图(To do list)中删除项目，长按不动。

Question 1

我想用sqlite做一个待办事项列表，当我在一个项目上按了很久，它就会从列表中被删除（同时也从数据库中删除）。但我无法实现，不知道如何删除（我是个新手）。我可以在setOnItemLongClickListener中做什么来删除数据库中的值？这是我的MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
    private ArrayList<String> items;
    private ArrayAdapter<String> itemsAdapter;
    private ListView lvItems;
    private EditText e;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final DatabaseHelper helper = new DatabaseHelper(this);
        lvItems = (ListView)findViewById(R.id.lvItems);
        items = helper.getAllAcontacts();
        itemsAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);
        lvItems.setAdapter(itemsAdapter);
        e = (EditText)findViewById(R.id.etNewItem);
        Button add = (Button)findViewById(R.id.btnAddItem);
        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(!e.getText().toString().isEmpty()) {
                    if (helper.insert(e.getText().toString())){
                        Toast.makeText(MainActivity.this, "Inserted", Toast.LENGTH_SHORT).show();
                    } else {
                        Toast.makeText(MainActivity.this, "Not Inserted", Toast.LENGTH_SHORT).show();
                else{
                    e.setError("Enter To Do List Item");
                items.clear();
                items.addAll(helper.getAllAcontacts());
                itemsAdapter.notifyDataSetChanged();
                lvItems.invalidateViews();
                lvItems.refreshDrawableState();
                e.setText("");
setupListViewListener();
private void setupListViewListener() {
        lvItems.setOnItemLongClickListener(
                new AdapterView.OnItemLongClickListener() {
                    @Override
                    public boolean onItemLongClick(AdapterView<?> adapter,
                                                   View item, int pos, long id) {
                        // Remove the item within array at position
                        items.remove(pos);
                        itemsAdapter.notifyDataSetChanged();
                        // Return true consumes the long click event (marks it handled)
                        return true;
而这是我的数据库删除功能。
public void deleteItem(long itemId) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(DatabaseHelper.LIST_TABLE_NAME, "_id = ?",
                new String[] { String.valueOf(itemId) });

Question 2


          
           
            我能够用游标来解决这个问题。主要的问题是，我的删除函数不能得到id，所以用游标来指向我想删除的特殊位置。工作代码是：。
           
           private void setupListViewListener() {
        lvItems.setOnItemLongClickListener(
                new AdapterView.OnItemLongClickListener() {
                    @Override
                    public boolean onItemLongClick(AdapterView<?> adapter,
                                                   View item, int pos, long id) {
                        AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(MainActivity.this);
                        dialogBuilder.setTitle("DELETE OR UPDATE");
                        dialogBuilder.setMessage("Write in text edit box and the tap on UPDATE to update value or simply tap on DELETE to delete value.");
                        dialogBuilder.setPositiveButton("Update", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                if(!e.getText().toString().isEmpty()) {
                                    if (helper.update(e.getText().toString(), pos)){
                                        Toast.makeText(MainActivity.this, "Updated!", Toast.LENGTH_LONG).show();
                                    } else {
                                        Toast.makeText(MainActivity.this, "Not Updated", Toast.LENGTH_SHORT).show();
                                else{
                                    e.setError("Enter To Do List Item");
                                items.clear();
                                items.addAll(helper.getAllAcontacts());
                                itemsAdapter.notifyDataSetChanged();
                                lvItems.invalidateViews();
                                lvItems.refreshDrawableState();
                                e.setText("");
                        dialogBuilder.setNegativeButton("Delete", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                items.remove(pos);
                                helper.deleteItem(pos);
                                itemsAdapter.notifyDataSetChanged();
                                dialog.cancel();
                        dialogBuilder.create();
                        dialogBuilder.show();
                        return true;
而在DatabaseHelper。
public void deleteItem(int pos) {
        SQLiteDatabase db = this.getWritableDatabase();
        List<Integer> database_ids= new ArrayList<Integer>();
        Cursor c = db.rawQuery("SELECT*FROM "+LIST_TABLE_NAME,null);
        while(c.moveToNext()){
            database_ids.add(Integer.parseInt(c.getString(0)));