无法从 Listview 中删除项目（待办事项列表），长按没有任何反应

Posted 2023-04-18

【中文标题】无法从 Listview 中删除项目（待办事项列表），长按没有任何反应

【英文标题】：Can't remove item from Listview(To do list), nothing is happening on long press

【发布时间】：2021-12-30 20:44:04

【问题描述】：

我正在尝试使用 sqlite 创建一个待办事项列表，当我长时间按下一个项目时，它将从列表（以及数据库）中删除。但我做不到，不明白如何删除（我是新手）。我还可以在 setOnItemLongClickListener 中做什么来从数据库中删除值？ 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;

                    
                );

    

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) );
    

【参考方案1】：

我能够使用光标解决它。主要问题是，我的删除功能无法获取 id，因此使用光标指向我想要删除的特殊位置。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;

                    
                );

    

在 DatabaseHelper 中：

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)));
        

        db.delete(LIST_TABLE_NAME, " id=?",
                new String[]  String.valueOf(database_ids.get(pos)) );
        c.close();