游标返回不正确的值

Question

我正在创建一个用于监控个人财务的应用程序。用户创建帐户、类别和交易。 dBHelper.java 类创建数据库，如下所示：

public void onCreate(SQLiteDatabase db) {
    //executes only once
    //create tables
    Log.v("TAG", "creating table:" +racuniTable);
    String sql = "create table " +racuniTable+" (" +colID+ " INTEGER PRIMARY KEY AUTOINCREMENT, " 
    +colName+ " TEXT, " +colValue+ " REAL, " +colAccType+ " TEXT);";

    Log.v("TAG", "creating table:" +transakcijeTable);
    String sql1 = "create table " +transakcijeTable+" (" +colTransID+ " INTEGER PRIMARY KEY AUTOINCREMENT, " 
    +colTransDate+ " DATE, "  +colAmount+ " REAL, " 
    +colIDracuni+ " INTEGER, " +colIDkategorije+ " INTEGER);";

    Log.v("TAG", "creating table:" +kategorijeTable);
    String sql2 = "create table " +kategorijeTable+" (" +colCatID+ " INTEGER PRIMARY KEY AUTOINCREMENT, " +colCatName+ " TEXT);";
    Log.v("TAG", "adding account:");

    db.execSQL(sql);
    db.execSQL(sql1);
    db.execSQL(sql2);
}

该函数创建三个数据库。当我尝试获取所有交易的列表或由 SQL 语句配置的任何其他报告时，就会出现问题：

private void getTransactions(){

    try {
        DbHelper dbHelper = new DbHelper(this.getApplicationContext());
        newDB = dbHelper.getWritableDatabase(); 
        m_transaction = new ArrayList<transaction>();
        Cursor c = newDB.rawQuery("SELECT rac.Ime, trans.Znesek, trans.Datum,   kate.Ime FROM Racuni AS rac, " + "Transakcije AS trans, Kategorije 
        as kate WHERE trans.ID_racuna=rac._id AND trans.ID_kategorije=kate._id", null);

        if (c != null ) {
            if  (c.moveToFirst()) {
                do {
                    String racun = c.getString(c.getColumnIndex("rac.Ime"));
                    double znesek = c.getDouble(c.getColumnIndex("trans.Znesek"));
                    String datum = c.getString(c.getColumnIndex("trans.Datum"));
                    String kategorija = c.getString(c.getColumnIndex("kate.Ime"));

                    transaction t1 = new transaction();
                    t1.setracun(racun);
                    t1.setznesek(znesek);
                    t1.setdatum(datum);
                    t1.setkategorija(kategorija);   

                    m_transaction.add(t1);

                }while (c.moveToNext());
            }
        }       
    } catch (SQLiteException se ) {
    Log.e(getClass().getSimpleName(), "Could not create or Open the database");
  }

我之前使用 Cursor 来显示帐户列表，并且效果很好。我不知道为什么它不再起作用了。我没有在表中使用外键或类似的东西，它应该可以工作。如果我执行代码，我将得到错误的值和大量错误。我在这些特定行上收到错误：

String racun = c.getString(c.getColumnIndex("rac.Ime"));
double znesek = c.getDouble(c.getColumnIndex("trans.Znesek"));
String datum = c.getString(c.getColumnIndex("trans.Datum"));
String kategorija = c.getString(c.getColumnIndex("kate.Ime"));

应用程序将运行，我将打印信息。所有打印的信息都是正确的。字符串 racun 与字符串 kategorija 相同，但它们不应该相同。我不确定为什么我总是从 racun 列中获取错误的值。我使用带有 adb shell 的 SQLite 3 测试了我的 SQL，它运行良好。以下是 LogCat 中的错误：

08-19 17:48:16.279: ERROR/Cursor(625): requesting column name with table name -- rac.Ime

08-19 17:48:16.331: ERROR/Cursor(625): requesting column name with table name -- trans.Znesek

08-19 17:48:16.359: ERROR/Cursor(625): requesting column name with table name -- trans.Datum

08-19 17:48:16.439: ERROR/Cursor(625): requesting column name with table name -- kate.Ime

是否因为我在 SQL 中使用了别名而出现了问题？这应该打印：

SELECT rac.Ime, trans.Znesek, trans.Datum, kate.Ime FROM Racuni AS rac, Transakcije AS trans, Kategorije as kate WHERE trans.ID_racuna=rac._id AND trans.ID_kate
    gorije=kate._id;
    Tomaz|50.0|3911-08-18|placa
    Tom|33.0|3912-07-18|placa
    Tomaz|70.0|3800-07-17|zapravlanje
    Tom|69.0|2010-07-17|placa
    Tomaz|30.0|2011-08-18|placa
    Tom|30.0|2011-08-12|zapravlanje
    Tom|50.0|2011-08-01|placa
    sqlite>

这是我收到的其余内容。关于如何解决这个问题有什么建议吗？

Answer 1

更改

SELECT rac.Ime, trans.Znesek, trans.Datum, kate.Ime FROM ...

为：

SELECT rac.Ime racun, trans.Znesek, trans.Datum, kate.Ime kategorja FROM ...

然后分别更改

c.getColumnIndex(...)

Answer 2

示例：

Table_1：id、名称、详细信息

Table_2：id、名称、价格

String ALL_COLUMNS_TABLE_2="Table_2.id _id, Table_2.name _name, Table_2.price _price";

Cursor cursor = db.rawQuery("select "+ Table_1 +".*,"+ALL_COLUMNS_TABLE_2+" from " + Table_1 + "," + Table_2,null);
try {
            if (cursor.moveToFirst()) {
                while (cursor.isAfterLast() == false) {

                    int idTable1 = cursor.getInt(cursor
                            .getColumnIndex("id"));
int idTable2 = cursor.getInt(cursor
                            .getColumnIndex("_id"));
....
}