Question

我已经用这个圈了几天，我无法理解错误。使用以下代码，当您按下＆＃34;是＆＃34;按钮删除您触摸的项目，它显示所有内容并且似乎执行所有操作，但项目未从列表中删除。

活动类：

package com1032.em00224.knit;

import java.util.ArrayList;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.view.KeyEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class NoteActivity extends Activity {

  private ListView list;    
   DatabaseHandler db;
   int id_To_Update = 0;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_note);

      db = new DatabaseHandler(this);
      ArrayList array_list = db.getAllNotes();

  ArrayAdapter arrayAdapter =      
  new ArrayAdapter(this,android.R.layout.simple_list_item_1, array_list);

  //adding it to the list view.
  list = (ListView)findViewById(R.id.listView1);
  list.setAdapter(arrayAdapter);

  list.setOnItemClickListener(new OnItemClickListener(){

 @Override
 public void onItemClick(AdapterView<?> parent, View arg1, final int position,
 long arg3) {
     // TODO Auto-generated method stub
     AlertDialog.Builder adb = new AlertDialog.Builder(NoteActivity.this); 
     adb.setTitle("Delete Note?");
     adb.setMessage(R.string.deleteNote); 
     adb.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
             db.deleteNote(position + 1);
             arrayAdapter.notifyDataSetChanged();
             Toast.makeText(getApplicationContext(), "Note Deleted", Toast.LENGTH_SHORT).show();
             Intent intent = new Intent(getApplicationContext(), com1032.em00224.knit.NoteActivity.class);
             startActivity(intent);
         }
     });
     adb.setNegativeButton(R.string.no, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
         }
     }); 
     adb.show();
 }
 }); 
 }

数据库助手：

package com1032.em00224.knit;

import java.util.ArrayList;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;

public class DatabaseHandler extends SQLiteOpenHelper {

   public static final String DATABASE_NAME = "NoteDatabase.db";
   public static final String NOTES_TABLE_NAME = "notes";
   public static final String NOTES_COLUMN_ID = "id";
   public static final String NOTES_COLUMN_NOTE = "note";

   public DatabaseHandler(Context context)
   {
      super(context, DATABASE_NAME , null, 1);
   }

   @Override
   public void onCreate(SQLiteDatabase db) {
      // TODO Auto-generated method stub
      db.execSQL(
      "create table notes " +
      "(id integer primary key, note text)"
     );
   }

   @Override
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      // TODO Auto-generated method stub
      db.execSQL("DROP TABLE IF EXISTS notes");
      onCreate(db);
  }

   public boolean insertNote  (String note)
 {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();

    contentValues.put("note", note);

    db.insert("notes", null, contentValues);
    return true;
 }
   public Cursor getData(int id){
      SQLiteDatabase db = this.getReadableDatabase();
     Cursor res =  db.rawQuery( "select * from contacts where id="+id+"", null );
     return res;
 }
 public int numberOfRows(){
    SQLiteDatabase db = this.getReadableDatabase();
    int numRows = (int) DatabaseUtils.queryNumEntries(db, NOTES_TABLE_NAME);
    return numRows;
 }
  public boolean updateNote (Integer id, String note)
  {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("note", note);
    db.update("notes", contentValues, "id = ? ", new String[] { Integer.toString(id) }     );
    return true;
 }

   public Integer deleteNote (Integer id)
 {
  SQLiteDatabase db = this.getWritableDatabase();
  return db.delete("notes", 
  "id = ? ", 
  new String[] { Integer.toString(id) });
 }

 public ArrayList getAllNotes()
 {
  ArrayList array_list = new ArrayList();
  SQLiteDatabase db = this.getReadableDatabase();
  Cursor res =  db.rawQuery( "select * from notes", null );
  res.moveToFirst();
  while(res.isAfterLast() == false){
  array_list.add(res.getString(res.getColumnIndex(NOTES_COLUMN_NOTE)));
  res.moveToNext();
  }
 return array_list;
 }
 }

其他所有内容，例如添加新项目，都可以正常运行。

编辑 - 它现在删除所选的一个，但它并不总是实际删除，似乎没有模式 - 我添加了一些system.out.printlns以获得更清晰的图片但它说当它不是时会删除正确的那个。

Answer 1

在某些项目中，我遇到了同样的问题。所以有两种可能的解决方案。首先，从数据库中删除您的数据后，还要从listview / Adapter中删除项目并调用notifyDataSetChanged：

   db.deleteNote(position);
   arrayAdapter.remove(arrayAdapter.getItem(itemToRemove));
   arrayAdapter.notifyDataSetChanged();

所以，我的问题是，这有时不起作用，直到现在，我不知道我做错了什么。无论如何，如果这不起作用，请在删除后刷新整个数据：

    private void refreshData(){

           ArrayList array_list = db.getAllNotes();
           ArrayAdapter arrayAdapter =      
            new ArrayAdapter(this,android.R.layout.simple_list_item_1, array_list);
            list.setAdapter(arrayAdapter);
            list.invalidateViews();

     }

所以这应该在你的onClick中看起来像这样：

     adb.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
      public void onClick(DialogInterface dialog, int id) {
         db.deleteNote(position);
         refreshData();
         Toast.makeText(getApplicationContext(), "Note Deleted", Toast.LENGTH_SHORT).show();
         Intent intent = new Intent(getApplicationContext(),  com1032.em00224.knit.NoteActivity.class);
         startActivity(intent);
     }
  });

这只是从头开始，我现在无法测试代码，因为我这里没有IDE。所以不要忘记做一些解决方法（比如打开和关闭数据库等）。

无法删除数据库项SQLite Android

1 个答案: