FWD » Core Development » User Interface

1. Convert, compile and run two procedures below.
2. Exit the main window by pressing ESC twice.

The program bumps into NPE in LogicalTerminal.refreshBuffers.

main.p:

SESSION:SYSTEM-ALERT-BOXES = TRUE.
RUN browse.p.
WAIT-FOR CLOSE OF THIS-PROCEDURE.

browse.p (the example from #5240-1 not minimalistic):

DEF TEMP-TABLE tt FIELD f1 AS CHARACTER FORMAT "x(32)".
CREATE tt.

OPEN QUERY q FOR EACH tt.

DEFINE BROWSE brws
   QUERY q DISPLAY tt.f1
   ENABLE ALL
   WITH TITLE "Browse" 
   SIZE 70 BY 7.

DEF FRAME fr brws WITH TITLE "Frame" SIZE 70 BY 15 NO-LABELS.
ENABLE ALL WITH FRAME fr.

brws:SELECT-ROW(1).
tt.f1:SCREEN-VALUE IN BROWSE brws = "16122021".
WAIT-FOR CLOSE OF THIS-PROCEDURE.

The problematic method looks as follows:

   public static void refreshBuffers(ScreenBuffer[] buffer)
   {
      if (buffer != null)
      {
         GenericFrame frame = getWidgetForId(buffer[0].getBaseId()).getFrame();

         handleScreenBuffers(frame, buffer, false);
      }
   }

Here getWidgetForId(buffer[0].getBaseId()) returns null.

From the stack traces I gather that the client sends the screen buffers update event to the server for the widget which is already unregistered on the server.

I suppose, we may just do nothing in this situation. The fixed method may look like:

   public static void refreshBuffers(ScreenBuffer[] buffer)
   {
      if (buffer == null)
      {
         return;
      }

      final GenericWidget<?> widget = getWidgetForId(buffer[0].getBaseId());
      if(widget == null)
      {
         return;
      }

      GenericFrame frame = widget.getFrame();

      handleScreenBuffers(frame, buffer, false);
   }