Never entering in cursor.moveToNext() in Android SQLite

Question

I'm trying Official Documentation for Android this article. Creating Database, Table and inserting data is working fine. But I'm unable to get data from database. Here is the piece of code to retrieve data from table.

public Person searchDataInDB(String personCellString) {
    SQLiteDatabase db = getReadableDatabase();

    // Define a projection that specifies which columns from the database
    // you will actually use after this query.
    String[] projection = {
            PersonTable.COLUMN_NAME_ID,
            PersonTable.COLUMN_NAME_NAME,
            PersonTable.COLUMN_NAME_CELL_NO,
            PersonTable.COLUMN_NAME_ADDRESS
    };

    // Filter results WHERE "cell#" = 'Person Cell #'
    String selection = SQLiteDBHelper.PersonTable.COLUMN_NAME_CELL_NO + " = ?";
    String[] selectionArgs = {"'" + personCellString + "'"};

    // How you want the results sorted in the resulting Cursor
    //  String sortOrder = SQLiteDBHelper.PersonTable.COLUMN_NAME_ID + " DESC";

    Cursor cursor = db.query(
            SQLiteDBHelper.PersonTable.TABLE_NAME,   // The table to query
            null,             // The array of columns to return (pass null to get all)
            selection,              // The columns for the WHERE clause
            selectionArgs,          // The values for the WHERE clause
            null,                   // don't group the rows
            null,                   // don't filter by row groups
            null               // The sort order
    );
    String [] names = cursor.getColumnNames();
    Log.e("SQLiteDB", "cursorCount = " + cursor.getCount() + ", cursorColumnCount = " + cursor.getColumnCount() + ", Column = " + names[0]);

    Person person = null;
    while (cursor.moveToNext()) {
        int id = (int) cursor.getLong(
                cursor.getColumnIndexOrThrow(PersonTable.COLUMN_NAME_ID));
        Log.e("SQLiteDB", "moveToNext id = " + id);
        String name = cursor.getString(
                cursor.getColumnIndexOrThrow(SQLiteDBHelper.PersonTable.COLUMN_NAME_NAME));
        Log.e("SQLiteDB", "moveToNext name = " + name);
        String cellNo = cursor.getString(
                cursor.getColumnIndexOrThrow(SQLiteDBHelper.PersonTable.COLUMN_NAME_CELL_NO));
        Log.e("SQLiteDB", "moveToNext cell = " + cellNo);
        String address = cursor.getString(
                cursor.getColumnIndexOrThrow(SQLiteDBHelper.PersonTable.COLUMN_NAME_ADDRESS));
        Log.e("SQLiteDB", "moveToNext address = " + address);
        person = new Person(id, name, cellNo, address);
    }
    cursor.close();

    return person;
}

It seems like my app does not enter in while loop i.e. while(cursor.moveToNext() So this method always returns initial value of person which is null. As a result, the first condition is always true from below code

Person person = dbHelper.searchDataInDB(personCellString);
     if (person == null) {
          Toast.makeText(mContext, "no such record exists in database!", Toast.LENGTH_LONG).show();
     } else {
         String personDetails = "Name = " + person.getName()
                  + "Cell Number = " + person.getCellNumber()
                  + "Address = " + person.getAddress();
         personDetailsTV.setText(personDetails);
     }

I'm using DB Browser for SQLite so I can see the records are successfully adding in the database.

What should I do with the above code to make it work?

Answer 1

What you are doing with this:

String[] selectionArgs = {"'" + personCellString + "'"};

is searching for the string value of personCellString enclosed inside single quotes and not for the actual value of the string personCellString.

Remove the single quotes:

String[] selectionArgs = {personCellString};

You don't have to worry about the string representation of personCellString in the final sql statement that will be constructed and executed which will contain them without explicitly setting them.