无法从数据库获取数据

Question

First of all i'm new to Android Development. I'm having some issues with fetching data from database. Whenever i try to fetch a data, the cursor is being empty.

Here is my code:

public ArrayList<Word> getWords(){

    SQLiteDatabase db = this.getReadableDatabase();
    String query = "SELECT * FROM " + TABLE_NAME;
    Cursor cursor = db.rawQuery(query, null);
    ArrayList<Word> List = new ArrayList<Word>();

    if(cursor != null){
            cursor.moveToFirst();
            while (cursor.moveToNext()){
            List.add(new Word(cursor.getString(cursor.getPosition())));
        }
    }
    cursor.close();
    db.close();
    return List;
}

The size of the cursor is always 1 but the size of the "List" variable is always 0.

I didn't understand the problem, thanks for helping me.

Answer 1

You are shifting the cursor position twice. Just remove the line cursor.moveToFirst(); The moveToNext method is sufficient as it moves to the first position on the first iteration.

Answer 2

you can use this code:

1-If you need first row:

if(cursor != null){
        cursor.moveToFirst();
        if(cursor.isAfterLast() == false){
        List.add(new Word(cursor.getString(cursor.getPosition())));
        }
}

2- if you need several rows :

if(cursor != null){
        cursor.moveToFirst();            
        while (cursor.isAfterLast() == false) {
        List.add(new Word(cursor.getString(cursor.getPosition())));
        cursor.moveToNext();
        }
}

Answer 3

I checked everything but your recommendations didn't worked. Just to be sure: I want to fetch all rows.

Answer 4

Try like this

public ArrayList<Word> getWords(){

    SQLiteDatabase db = this.getReadableDatabase();
    String query = "SELECT * FROM " + TABLE_NAME;
    Cursor cursor = db.rawQuery(query, null);
    ArrayList<Word> list = new ArrayList<Word>();

    if(cursor != null){
        while (cursor.moveToNext()){
            list.add(new Word(cursor.getString(cursor.getPosition())));
        }
    }
    cursor.close();
    db.close();
    return list;
}

Answer 5

I just realised that the program does not go into the while loop in the code that i given above. I think there is a problem with database.

I used that query to create database:

private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + TABLE_NAME + " (" +
                    COLUMN_NAME_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    COLUMN_NAME_TURKISH + " TEXT, " +
                    COLUMN_NAME_ENGLISH + " TEXT, " +
                    COLUMN_NAME_GERMAN + " TEXT, " +
                    COLUMN_NAME_FRENCH + " TEXT, " +
                    COLUMN_NAME_ARABIC + " TEXT, " +
                    COLUMN_NAME_RUSSIAN + " TEXT, " +
                    COLUMN_NAME_SPANISH + " TEXT, " +
                    COLUMN_NAME_ITALIAN + " TEXT)";

Answer 6

I feel like a idiot because i forgot to type the database name at the constructor method like that:

Old

super(context, null, null, 1);

Now

super(context, "database", null, 1);

Thanks for your help!