Index 0 Requested with a size of 0 Error in SQLITE DB

Question

There is data in the database (2 rows to be precise) with info in each.

Here is the code (that matters, not all of it) from the DBADAPTER:

// Field Names:
    public static final String KEY_ROWID = "_id";
    public static final String KEY_DEVICE = "device";
    public static final String KEY_TYPE = "type";
    public static final String KEY_DEVID = "devid";

    public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_DEVICE, KEY_TYPE, KEY_DEVID};
    public static final String[] DEVID_KEY = new String[] {KEY_DEVID};

    // Column Numbers for each Field Name:
    public static final int COL_ROWID = 0;
    public static final int COL_DEVICE = 1;
    public static final int COL_TYPE = 2;
    public static final int COL_DEVID = 3;

    // DataBase info:
    public static final String DATABASE_NAME = "dbDevices";
    public static final String DATABASE_TABLE = "mainDevices";
    public static final int DATABASE_VERSION = 10; // The version number must be incremented each time a change to DB structure occurs.

    //SQL statement to create database
    private static final String DATABASE_CREATE_SQL = 
            "CREATE TABLE " + DATABASE_TABLE 
            + " (" + KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
            + KEY_DEVICE + " TEXT NOT NULL, "
            + KEY_TYPE + " TEXT, "
            + KEY_DEVID + " TEXT NOT NULL "
            + ");";

    private final Context context;
    private DatabaseHelper myDBHelper;
    private SQLiteDatabase db;

    // Get a specific row (by devid)
        public String getDevName(String devid) {
            String name;
            String where = KEY_DEVID + " like '%" + devid + "%'";
            Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                            where, null, null, null, null, null);
                c.moveToFirst();
                name = c.getString(COL_DEVICE);
            return name;
        }

Here is the code that calls it:

String incomingMessage = " ";
incomingMessage = in.readLine() + System.getProperty("line.separator");
devName = devDB.getDevName(incomingMessage);

And I know that this is getting it info because it logs:
03-16 15:39:47.072: V/String(18073): 5122

Whenever I run this I get the error:

03-16 15:39:47.122: W/System.err(18073): android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
03-16 15:39:47.122: W/System.err(18073):    at android.database.AbstractCursor.checkPosition(AbstractCursor.java:426)
03-16 15:39:47.122: W/System.err(18073):    at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:136)
03-16 15:39:47.132: W/System.err(18073):    at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:50)
03-16 15:39:47.132: W/System.err(18073):    at com.ti.cc3x.android.DBAdapter.getDevName(DBAdapter.java:121)
03-16 15:39:47.132: W/System.err(18073):    at com.ti.cc3x.android.broadcastListener$1.run(broadcastListener.java:112)
03-16 15:39:47.132: W/System.err(18073):    at java.lang.Thread.run(Thread.java:841)

I have tried checking for not null cursor. All that does is tell me nothing. I know there is data where I am asking it to look I just do not know why it will not show it. Can anyone tell me where I went wrong? Thank you!

Answer 1

Are you using SQLiteOpenHelper? If so you you need to set your database variable db to your database before attempting to read from or write to it like so:

db = this.getWritableDatabase();

... your new getDevName(..) method should look something like this:

public String getDevName(String devid) {
    db = this.getWritableDatabase();

    String name;
    String where = KEY_DEVID + " like '%" + devid + "%'";
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, 
                    where, null, null, null, null, null);
    c.moveToFirst();
    name = c.getString(COL_DEVICE);

    db.close(); // close your db connection when you're done with it

    return name;
}

From the Android Developer documentation:

public SQLiteDatabase getWritableDatabase () - The first time this is called, the database will be opened and onCreate(SQLiteDatabase), onUpgrade(SQLiteDatabase, int, int) and/or onOpen(SQLiteDatabase) will be called. Once opened successfully, the database is cached, so you can call this method every time you need to write to the database. (Make sure to call close() when you no longer need the database.) Errors such as bad permissions or a full disk may cause this method to fail, but future attempts may succeed if the problem is fixed.