android - SQLite 异常 : Unrecognized token when reading from database

Question

我在应用程序中创建了一个 SQLite 数据库，填充了它，现在我正在尝试从中读取。该应用程序不断崩溃，这是我收到的 logcat:

12-30 05:53:18.008: E/AndroidRuntime(6205): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testparsing/com.example.testparsing.Urnik}: android.database.sqlite.SQLiteException: unrecognized token: "4c" (code 1): , while compiling: SELECT predmet FROM predmeti WHERE dan=PONEDELJEK and ura=2 and oddelek=4c

从数据库读取函数:

Cursor getSubject(String dan, int ura, String oddelek){
    String[] columnNames = new String[1];
    columnNames[0] = SQLiteHelper.PREDMET;
    String selection = SQLiteHelper.DAN+"="+dan+" and "+SQLiteHelper.URA+"="+ura+" and "+SQLiteHelper.ODDELEK+"="+oddelek;
    open();
    return db.query(
            SQLiteHelper.IME_TABELE, 
            columnNames, 
            selection, 
            null, null, null, null);
}

我的阅读方式:

TextView tw1p = (TextView) findViewById(R.id.tview1p);
DatabaseHandler db = new DatabaseHandler(getApplicationContext());

Cursor c = db.getSubject("PONEDELJEK", 2, "4c");
String predmet = c.getString(c.getColumnIndex(SQLiteHelper.PREDMET));
tw1p.setText(predmet);

表格截图，只是为了证明oddelek“4c”确实存在:

Answer 1

SELECT predmet FROM predmeti WHERE dan=PONEDELJEK and ura=2 and oddelek=4c

您需要引用您的字符串文字，例如:

SELECT predmet FROM predmeti WHERE dan='PONEDELJEK' and ura=2 and oddelek='4c'

但是最好使用 ? 占位符来表示文字:

SELECT predmet FROM predmeti WHERE dan=? and ura=? and oddelek=?

并将您的 null selectionArgs 更改为

new String[] { dan, Integer.toString(ura), oddelek }