The null pointer in this case is in the framework, not my code. I am using
VSCode, pausing on exceptions is enabled, as well as pausing on uncaught
exceptions.
The problem is, no exception is thrown. No error exists. Rendering just stops
for whatever component encounters the NP.
To see what I'm talking about, try creating a VirtualList (jewel) without a
ListPresentationModel. It will not render at all due to the NP. No errors, no
exceptions.
Perhaps my first email was a bit misleading because I kept using NPE, when
really it's NPs without the E.
I've noticed this same behavior within my own code. It's as is something is
catching these and suppressing them.
The following will show my issue:
<j:VirtualList
width="100%"
dataProvider="{someDataProvider}"
itemRenderer="com.some.ItemRenderer">
<j:beads>
<!-- <j:ListPresentationModel rowHeight="80" /> -->
</j:beads>
</j:VirtualList>
-----Original Message-----
From: Yishay Weiss <[email protected]>
Sent: Thursday, March 11, 2021 4:21 AM
To: [email protected]
Subject: [EXTERNAL] Re: Royale & NPE Behavior
You got:
>Without, the code will throw a null pointer exception resulting in an empty
>list being displayed.
And you expect:
>Bare minimum, it would be nice to at least see an uncaught exception with the
>debugger.
Can you explain the difference? If what you need is for the debugger to halt
execution with a stack trace, then you can switch on 'pause on exceptions' in
the dev tools. I must be missing something...
________________________________
From: Brian Raymes <[email protected]>
Sent: Wednesday, March 10, 2021 7:16 PM
To: [email protected] <[email protected]>
Subject: Royale & NPE Behavior
Hi all,
I've been noticing a problem with Royale that I think is time to bring up with
the greater audience.
What is the expected behavior when encountering an NPE within a Royale
application? I've notice that NPEs seem to break the UI with no notice of any
kind.
For example, I recently started trying out VirtualLists. For quite some time, I
could not figure out why they would not render any of my data. It turns out,
Virtual list requires the bead ListPresentationModel with a non-null rowHeight.
This is due to VirtualListVerticalLayout's layout method assuming the existence
of an IListPresentationModel. Without, the code will throw a null pointer
exception resulting in an empty list being displayed.
The problem I want to highlight is that as a developer, without diving through
the framework code, and ultimately guessing on trying various things
beforehand, there was no way for me to know that happened. There is no console
log output stating the error, no uncaught exception for the debugger to catch,
and no visible reasoning for what is occurring.
Is this the expected behavior, or can this be improved? I've wasted a
surprising amount of time chasing these issues in the past year while working
with Royale.
Bare minimum, it would be nice to at least see an uncaught exception with the
debugger.
Brian
