Android sqlite 选择不工作

Question

我使用 sqllite.i 成功创建了 sql 数据库，我也可以插入一些值并在 ListView 中显示它。现在我想编写函数女巫返回标题，其中 ServerID 喜欢我的值我写了函数但是这个函数没有返回计数器

public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "lv_db4";
private static final String TABLE_CONTACTS = "CardTable1";
public static final String KEY_ID = "id";

private static final String KEY_Tittle = "title";
private static final String KEY_Description = "description";
private static final String KEY_Price = "price";
private static final String KEY_Counter = "counter";

private static final String KEY_ServerId = "serverid";
private static final String KEY_Image = "image";
private final ArrayList<Contact> contact_list = new ArrayList<Contact>();
public static SQLiteDatabase db;


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

@Override
public void onCreate(SQLiteDatabase db) {
    String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
            + KEY_ID + " INTEGER PRIMARY KEY,"

            + KEY_Tittle + " TEXT,"

            + KEY_Description + " TEXT,"

            + KEY_Price + " TEXT,"

            + KEY_Counter + " TEXT,"

            + KEY_ServerId + " TEXT,"

            + KEY_Image + " TEXT"

            + ");";
    db.execSQL(CREATE_CONTACTS_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
    onCreate(db);
}

// Adding new contact
public void Add_Contact(Contact contact) {
    db = this.getWritableDatabase();
    ContentValues values = new ContentValues();

    values.put(KEY_Tittle, contact.getTitle());
    values.put(KEY_Description, contact.getDescription());
    values.put(KEY_Price, contact.getPrice());

    values.put(KEY_Counter, contact.getCounter());

    values.put(KEY_ServerId, contact.getServerId());

    values.put(KEY_Image, contact.getImage());

    db.insert(TABLE_CONTACTS, null, values);

    db.close();

}

public void deleteUser(String userName) {
    db = this.getWritableDatabase();
    try {
        db.delete(TABLE_CONTACTS, "title = ?", new String[] { userName });

    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        db.close();
    }
}

public String GetCounterFromServerID(String value) {



    db = this.getWritableDatabase();

    Cursor cursor = db.rawQuery("select " + KEY_Counter+  " from " + TABLE_CONTACTS
            + " where serverid like '%" + value + "%'", null);


    cursor.close();
    return KEY_Counter;

}

public int Update_Contact(Contact contact) {
    db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_Counter, contact.getCounter());

    // updating row
    return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
            new String[] { String.valueOf(contact.getID()) });
}

// Getting single contact
Contact Get_Contact(int id) {
    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
            KEY_Tittle, KEY_Description, KEY_Price, KEY_Counter,
            KEY_ServerId, KEY_Image }, KEY_ID + "=?",
            new String[] { String.valueOf(id) }, null, null, null);
    if (cursor != null)
        cursor.moveToFirst();

    Contact contact = new Contact(cursor.getString(0), cursor.getString(1),
            cursor.getString(2), cursor.getString(3), cursor.getString(4),
            cursor.getString(5));

    cursor.close();
    db.close();

    return contact;
}

public boolean DublicateValues(String S_title) {
    db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery("select * from " + TABLE_CONTACTS
            + " where title like '%" + S_title + "%'", null);
    boolean exists = (cursor.getCount() > 0);

    cursor.close();
    return exists;
}

我的 GetCounterFromServerID 函数只返回“计数器”，我想返回例如 2 或 4 等

我在另一个 Activity 中这样调用我的函数:

 String counter;
                    counter=dbHandler.GetCounterFromServerID(intentServerId);
                    System.out.println(counter );

                    dbHandler.close();

日志结果只有计数器我究竟做错了什么？如果有人知道解决方案请帮助我

Answer 1

你可以这样做。

   public String GetCounterFromServerID(String value)
   {
     Cursor cursor = db.rawQuery("SELECT " + KEY_Counter + " FROM " + TABLE_CONTACTS + " WHERE serverid like '%" + value + "%'", null);

     if (!cursor.moveToFirst())
     {
         return null;
     }
     if(-1 == cursor.getColumnIndex(KEY_Counter)) 
     {
         return null;
     }
     String counter = cursor.getString(cursor.getColumnIndex(KEY_Counter));
     cursor.close();
     return counter;
  }