Getting one column of SQLite DB to ListView not working in Android

Question

I'm trying to retrieve a column (a database column where names are saved) and puting them to a listview. I have a class called Data with "getters" and "setters".

The following code is placed in a DBHandler class which extends SQLiteOpenHelper. This code is called from the MainActivity.java where the listview is meant to be updated with an onClickButton event.

public String[] getNames (int a, int b) { 

        String[] names = new String[] {};

        String selectQuery = "SELECT * FROM " + TABLE_NAME 
                + " WHERE " + KEY_ONE + " = ? AND " + KEY_TWO + " = ?";


        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, new String[]{String.valueOf(a), String.valueOf(b)});

        if (cursor.moveToFirst()) {

            int i = 0;

            do {
                Data myData = new Data();

                names [i] = cursor.getString(1); //Names in cursor

                ++i;

            } while (cursor.moveToNext());

        }
        return names;
    }

In the MainActivity.java I call the following code before updating and notifying the update of the listview adapter:

values = db.getNames (1, 1);

I don't know why but this isn't working, it throws many errors with String lengths and crashes the app when I click the button that is suposed to enter the onClickButton.

Thanks

Please upload those error logs

Lucifer
– Lucifer

2014-04-11 08:07:37 +00:00
Commented Apr 11, 2014 at 8:07 — Lucifer
– Lucifer, Commented Apr 11, 2014 at 8:07

M D · Accepted Answer · 2014-04-11 08:15:23Z

1

Follow the laalto answer and at last convert your ArrayList to Array like below:

String[] arrRecords = names.toArray(new String[names.size()]);

answered Apr 11, 2014 at 8:15

M D

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Comments

laalto · Accepted Answer · 2014-04-11 08:15:07Z

0

String[] names = new String[] {};

...

names [i] = cursor.getString(1); //Names in cursor

You're assigning to an empty array which causes ArrayIndexOutOfBoundsException.

Consider using a list such as ArrayList where you can append your values, e.g.

List<String> names = new ArrayList<String>();

...

names.add(cursor.getString(1));

If you really need to return a String[], you can convert the list with toArray():

String[] arr = new String[names.size()];
names.toArray(arr);
return arr;

Also, when posting questions that involve exceptions, always include the exception stacktrace from logcat in the question itself.

edited Apr 11, 2014 at 8:15

answered Apr 11, 2014 at 8:08

laalto

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3 Comments

user1903 Over a year ago

How can I change that ArrayList to a String[] which is what I really need after all?

laalto Over a year ago

There's toArray(T[] array)

user1903 Over a year ago

Is the other way, I need a String[] and I have an ArrayList

Wundwin Born · Accepted Answer · 2014-04-11 08:16:04Z

0

Why use like this

 String[] names = new String[] {}; //no size

 names [i] = cursor.getString(1); //it can work?

Use ArrayList<String>

List<String> names = new ArrayList<String>(); //declare

names.add(<column-val>);  //add column value to list

answered Apr 11, 2014 at 8:16

Wundwin Born

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