What is The use of moveToFirst () in SQLite Cursors

Question

I am a programming newbie and I found this piece of code in the internet and it works fine

Cursor c=db.query(DataBase.TB_NAME, new String[] {DataBase.KEY_ROW         


        

Answer 1

what macio.Jun says is right!

we have code like below:

    String sql = "select id,title,url,singer,view,info from cache where id=" + id;
    SQLiteDatabase db = getMaintainer().getReadableDatabase();
    Cursor query = db.rawQuery(sql, null);
    query.moveToFirst(); 
    while(query.moveToNext()){
        DBMusicData entity = new DBMusicData();
        entity.setId(query.getString(query.getColumnIndex(FIELD_ID)));
        entity.setTitle(query.getString(query.getColumnIndex(FIELD_TITLE)));
        entity.setSinger(query.getString(query.getColumnIndex(FIELD_SINGER)));
        entity.setTitlepic(query.getString(query.getColumnIndex(FIELD_PICURL)));
        entity.setInfoUrl(query.getString(query.getColumnIndex(FIELD_INFO)));
        entity.setViews(query.getString(query.getColumnIndex(FIELD_VIEW)));
        Log.w(tag, "cache:"+ entity.toString());
    }
    query.close();
    query=null;
    db.close();
    db=null;

If we have only one record in the cache table, query.moveToFirst(); will cause that no record returns.