Interface CursorExt

All Superinterfaces:
Cursor
public interface CursorExt extends Cursor

Optional cursor capabilities, in the same spirit as RowExt.

These are not on Cursor itself because that interface is public and is implemented outside this repository; adding a method to it would break every third party library that provides one. Reach these through the static helpers on Database, which degrade gracefully on a cursor that does not implement this interface:

Database.beforeFirst(cursor);
int rows = Database.count(cursor); // -1 when the port cannot say cheaply

Every cursor returned by a Codename One port implements this.

  • Method Details

    • beforeFirst

      void beforeFirst() throws IOException

      Rewinds to before the first row, without landing on a row.

      After this call Cursor#getPosition() reports -1 and Cursor#getRow() throws, exactly as on a freshly returned cursor. This is the operation Cursor#position(int) performs when given -1.

      Throws
      • IOException: if the cursor is closed or the rewind fails
      Throws:
      IOException

    • getCount

      int getCount() throws IOException

      Returns the number of rows in the result set, or -1 where a port cannot determine it.

      This can be expensive. Ports whose engine already tracks the count -- Android -- report it directly. Ports backed by a forward-only statement, which is the rest of them, answer by walking: rewind, step through every row, and rewind again. That is a full scan of the result set, so calling it on a large query costs what the query costs, and doing so on the EDT stops the application for that long. The count is remembered afterwards, and a rewind through #beforeFirst() drops it, since the next pass may not see the same rows.

      -1 means the port cannot answer at all. Treat it as "unknown", not as "empty".

      Returns

      the row count, or -1 where the port cannot determine it

      Throws
      • IOException: if the cursor is closed
      Throws:
      IOException