Closing cursors/database in Android

Question

Here is the code:

public List<XImage> getXImages()
{
    List<XImage> images = new ArrayList<XImage>();

    SQLiteDatabase database = this.getWritableDatabase();

    String sql = String.format("SELECT %s, %s, %s FROM %s",
            A, B, C, TABLE);

    Cursor result = database.rawQuery(sql, null);

    if (result.moveToFirst())
    {
        do
        {
            String a = result.getString(0);
            String b = result.getString(1);
            String c = result.getString(2);

            XImage image = new XImage(a, b, c);
            images.add(image);
        }

        while (result.moveToNext());
    }

    result.close();
    database.close();

    return images;  
}

If after result.close(); I put database.close(); I get a runtime exception saying that it's trying to access SqliteDatabase while the connection is closed.

Does closing the cursor also close the database connection? If not, what should I be doing differently?

score 2 · Answer 1 · answered Sep 01 '15 at 08:53

2

I had similar problems before, in the end of every method that works with the database, I had database.close(); and sometimes that throwed exceptions.

Remove database.close(); from around your code, and keep only the cursor close statements, and you should be fine.

answered Sep 01 '15 at 08:53

Borislav

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Thank you - but what is the reason for this? – b85411 Sep 02 '15 at 00:33
@b85411 If you close the database, the cursors can no longer be read from. – Karakuri Sep 07 '15 at 23:11

score 0 · Answer 2 · answered Sep 01 '15 at 09:07

I guess you are calling the method from different threads.

However in my opinion, the best practice is never close the database because SQLiteOpenHelper.getWritableDatabase() and SQLiteOpenHelper.getReadablDatabase() always return the same instance if SQLiteOpenHelper.close() hasn't been called. So calling method like yours would mess up the SQLiteDatabase instance's life cycle which rises exceptions.

You might want to check this link out:

http://touchlabblog.tumblr.com/post/24474750219/single-sqlite-connection

or source code of SQLiteOpenHelper here:

https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/android/database/sqlite/SQLiteOpenHelper.java

Closing cursors/database in Android

2 Answers2