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Hi Ross,<br>
<br>
Fair enough, but it sounds like these "random" crashes may be
starting to cause enough problems to consider investing the time and
effort to modify your approach - just a thought I guess.<br>
<br>
The difference, if I'm not mistaken, is that having the data stored
in a separate structure and dynamically loading into the ListView
would remove the problems caused by RecreateWnd. I might be wrong,
so just my two cents worth.<br>
<br>
Regards,<br>
<br>
Bevan<br>
<br>
<br>
<div class="moz-cite-prefix">On 12/04/2013 12:12 a.m., Ross Levis
wrote:<br>
</div>
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
didn’t read your final sentence. I already use virtual
listviews in other areas of this app and in other apps so
know all about them. That is what I would likely use if I
was to rewrite this app.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I’m
still not convinced Windows wouldn’t still execute a
RecreateWnd at any time and cause a problem in the OnData
procedure.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ross.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US"> Ross Levis
[<a class="moz-txt-link-freetext" href="mailto:ross@stationplaylist.com">mailto:ross@stationplaylist.com</a>] <br>
<b>Sent:</b> Friday, 12 April 2013 12:09 a.m.<br>
<b>To:</b> 'NZ Borland Developers Group - Delphi List'<br>
<b>Subject:</b> RE: [DUG] TListitems disappearing and
reappearing causing access violations<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">It’s
only a little function used by some users where a small
number of the TlistView items are stored in a TList. That
has been an issue on some occasions, but it’s not related to
most of the crashes which simply involve enumerating the
TListView Items.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
did mentioned if I was to write the app now, I would use the
Data property to point to data storage structures. It is 10
years old now and probably too much work to change all that.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
also need to alter the appearance of the list items, mostly
just the imageindex of the song file that is currently
playing, so I will need a link back to the TlistItem, or
perhaps do a TListView.IndexofData to find the relevant
listitem. But I can imagine sometimes that will return -1
(not found) or a listitem pointer that has been freed. So I
don’t know it’s going to help much.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ross.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a>
[<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Bevan Edwards<br>
<b>Sent:</b> Thursday, 11 April 2013 11:53 p.m.<br>
<b>To:</b> NZ Borland Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] TListitems disappearing and
reappearing causing access violations<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Ross,<br>
<br>
Have you perhaps thought that you have approached this in the
wrong way?<br>
It is clearly a mistake to maintain a list of TListItems
external to the TListView control. I believe you would be
better off maintaining your list of objects/records with the
appropriate structure, and then dynamically fill the TListView
based on that information.<br>
<br>
Check the help about virtual list views and the OnData event.<br>
<br>
Regards,<br>
<br>
Bevan<o:p></o:p></p>
<div>
<p class="MsoNormal">On 11/04/2013 3:52 p.m., Ross Levis
wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Yes
I realize that, but I didn’t know that was possible with
TListItems which the VCL manages for you. I need to know
what situations will cause that. I really need access to
all the items in the listview immediately at any time.
The app will not run correctly if something is freeing
list items willy nilly.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Presumably
a RecreateWnd() is being executed on the ListView for some
reason other than any code in the software. I’ve checked
the VCL source code for TCustomListView and where
RecreateWnd is being executed, and it’s only with a change
to a handful of Properties which I am not altering in
code. So Windows is doing this itself for some reason.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
think I will have to subclass the TListView's WindowProc
property to look for CM_RECREATEWND and WM_DESTROY
messages, and stop all processing until this is finished.
Hopefully that will sort it out. What a bloody hassle.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ross.</span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a>
[<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Todd Martin<br>
<b>Sent:</b> Thursday, 11 April 2013 10:04 a.m.<br>
<b>To:</b> NZ Borland Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] TListitems disappearing and
reappearing causing access violations</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hi Ross<br>
<br>
Clearly the problem is NOT that the items are being removed
from the list. Rather the items are being freed, (from
previous comments) in various places, yet not removed. <br>
<br>
Just because <span
style="font-family:"Calibri","sans-serif"">assigned(PlayView.Items[i])
is true, does not mean that that instance exists. It means
that the object pointer is not nil. Do you understand the
difference between a nil pointer and a pointer to memory
that is no longer in use?<br>
<br>
Todd.<br>
<br>
<br>
<br>
</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">I’ve
heard today that TeamViewer isn’t in use when the problem
occurs. They often use it to resolve the issue after the
problem has occurred.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">They
tell me they have seen it in mid-song where all the tracks
disappear and the app then becomes unresponsive or crashes
because of the app still accessing items that don’t exist.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">There
are no deletion routines in the program which delete every
item from the listview, so that’s not what’s going on.
Considering there are around 5000 users who have no
problems at all, I don’t think it can be a coding
problem. There has been the very rare issue like this
reported over the years but this one user is getting it
regularly, like every couple of days.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">I
thought I was on to something with remote control app but
it appears not. </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">Another
reported crash a couple of weeks ago was here…</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">i
:= Item.Index;</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">while
(i < PlayView.Items.Count) and
(PlayView.Items[i].Caption = EventTimeStr) do</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">…</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">The
“while” line crashed with Access Violation in
ComCtrls.TListItems.GetItem, and the screen shot again
showed no items. This should prove that it cannot be the
software removing the items as otherwise Items.Count would
be 0.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">Someone
else with dual monitors had a crash on the same line about
6 months ago and it has now been modified to validate
items[i] is a real item before retrieving the caption.
This will stop the error but the software will not
function correctly.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">Cheers.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid windowtext
1.0pt;padding:3.0pt 0cm 0cm
0cm;border-color:-moz-use-text-color -moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a>
[<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Ross Levis<br>
<b>Sent:</b> Wednesday, 10 April 2013 2:38 a.m.<br>
<b>To:</b> 'NZ Borland Developers Group - Delphi List'<br>
<b>Subject:</b> Re: [DUG] TListitems disappearing and
reappearing causing access violations</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">I
guess I am. It makes the most sense. I’ll have to try a
test with TeamViewer to duplicate it.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> </span><o:p></o:p></p>
<div style="border:none;border-top:solid windowtext
1.0pt;padding:3.0pt 0cm 0cm 0cm;border-color:rgb(181,
196,
223) -moz-use-text-color -moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">delphi-bounces@listserver.123.net.nz</a>
[<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz">mailto:delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Kyley Harris<br>
<b>Sent:</b> Wednesday, 10 April 2013 12:48 a.m.<br>
<b>To:</b> NZ Borland Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] TListitems disappearing and
reappearing causing access violations</span><o:p></o:p></p>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt">I think
the problem is that right now you are running on the
Theory that they are being reconstructed as you state,
and you have not created a test scenario to validate
what you are saying. <o:p></o:p></p>
</div>
<p class="MsoNormal">it could just be a coding error, and
the delete event will tell you when a list item is being
destroyed. That list item will not be destroyed if the
window handle is reconstructed. Not in the source code I
can see.,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"> <o:p></o:p></p>
<div>
<p class="MsoNormal">On Wed, Apr 10, 2013 at 12:41 AM,
Ross Levis <<a moz-do-not-send="true"
href="mailto:ross@stationplaylist.com" target="_blank">ross@stationplaylist.com</a>>
wrote:<o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Actually
that doesn’t help so much. I really need to know
when Windows is deleting the items. My app also
deletes items. I guess I could remove the
OnDeletion event property before coding a delete
and reinstate if afterwards. A little messy.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
really need to associate the individual deleted
items with the identical new items that will be
created just afterwards. Ideally I would want my
app to stop processing all timers and functions
while the deletions and recreations are done.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Getting
too complicated.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<div style="border:none;border-top:solid windowtext
1.0pt;padding:3.0pt 0cm 0cm
0cm;border-color:-moz-use-text-color
-moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz"
target="_blank">delphi-bounces@listserver.123.net.nz</a>
[mailto:<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz"
target="_blank">delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Kyley Harris</span><o:p></o:p></p>
<div>
<p class="MsoNormal"><br>
<b>Sent:</b> Wednesday, 10 April 2013 12:06 a.m.<o:p></o:p></p>
</div>
<div>
<div>
<p class="MsoNormal"><b>To:</b> NZ Borland
Developers Group - Delphi List<br>
<b>Subject:</b> Re: [DUG] TListitems
disappearing and reappearing causing access
violations<o:p></o:p></p>
</div>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<p class="MsoNormal">the listview has an
Ondeletion event. when that fires, you should
check the index, and remove any listitem
references from your tlist. <br>
<br>
The issue seems to be that you are mixing view
objects with data objects. the system might go
more smoothly if you were containing your data
objects disctinct from your view (tlistview)
and synchronizing the view to the source. <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt"> <o:p></o:p></p>
<div>
<p class="MsoNormal">On Tue, Apr 9, 2013 at
11:58 PM, Ross Levis <<a
moz-do-not-send="true"
href="mailto:ross@stationplaylist.com"
target="_blank">ross@stationplaylist.com</a>>
wrote:<o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">It
isn’t a user initiated procedure.
It’s a broadcast media player in
automation mode and each track is a
listitem. Items can be dropped off
the top and more added to the bottom
as it plays automated.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">There
is a TTimer which accesses all the
items in the list once a second to
provide totals and such. So the items
are accessed very regularly.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Some
of the list items are timed events
which need to occur at a specific
time. These item pointers are stored
in a TList so the software can easily
access the next one without having to
look for it in the list.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">This
user has had issues with the code that
accesses this TList of TListitem
pointers, so that sounds like the
pointers to the listitems have been
changed.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ideally
the listitems shouldn’t be accessed
directly and a separate data store
should be used that is linked to each
item via the Data property. A bit too
late for that now though.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">So
it sounds like I need to find the
Windows message that is being sent to
the app to recreate windows and do
some housekeeping.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Any
ideas what that might be?</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<div style="border:none;border-top:solid
windowtext 1.0pt;padding:3.0pt 0cm 0cm
0cm;border-color:-moz-use-text-color
-moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a
moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz"
target="_blank">delphi-bounces@listserver.123.net.nz</a>
[mailto:<a moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz"
target="_blank">delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Kyley Harris<br>
<b>Sent:</b> Tuesday, 9 April 2013
11:35 p.m.</span><o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><br>
<b>To:</b> NZ Borland Developers
Group - Delphi List<br>
<b>Subject:</b> Re: [DUG]
TListitems disappearing and
reappearing causing access
violations<o:p></o:p></p>
</div>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt">If
that was the case.. then its
unlikely to happen midstream
during a very small short
procedure call. Especially if
that procedure call is a user
initiated one. <o:p></o:p></p>
</div>
<p class="MsoNormal">if that is the
case.. its extremely simple to
test this with remote desktop and
some logging of the
construction/destruction of the
list items.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt"> <o:p></o:p></p>
<div>
<p class="MsoNormal">On Tue, Apr
9, 2013 at 11:29 PM, Ross Levis
<<a moz-do-not-send="true"
href="mailto:ross@stationplaylist.com"
target="_blank">ross@stationplaylist.com</a>>
wrote:<o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I’ve
had someone suggest this
elsewhere…</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><i><span
style="font-family:"Calibri","sans-serif"">The user
connects a monitor to a
laptop, or connects
remotely via <br>
terminal services.<br>
Basically, anything that
changes the display
resolution has that kind
of <br>
consequences.</span></i><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I
have seen a TeamViewer in
one of the many screen
shots. So I guess Windows
is recreating the windows
and allocating new handles
to the list items as I
thought. I’ll check with
them if the crashes
coincide with use of
TeamViewer.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ross.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<div>
<div
style="border:none;border-top:solid
windowtext
1.0pt;padding:3.0pt 0cm
0cm
0cm;border-color:rgb(181,
196, 223)
-moz-use-text-color
-moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> Ross
Levis [mailto:<a
moz-do-not-send="true"
href="mailto:ross@stationplaylist.com" target="_blank">ross@stationplaylist.com</a>]
<br>
<b>Sent:</b> Tuesday,
9 April 2013 11:17
p.m.<br>
<b>To:</b> 'NZ Borland
Developers Group -
Delphi List'<br>
<b>Subject:</b> RE:
[DUG] TListitems
disappearing and
reappearing causing
access violations</span><o:p></o:p></p>
</div>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">The
list is populated by the
software. It’s still in
Delphi 7.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">No
threads are deleting any
items. Only the main
thread adds and removes
items.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">There
is no one procedure this
has occurred in. It can
work for 2 days and
suddenly this happens in
a random procedure that
accesses a list item.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">In
this particular case, it
is in a procedure where
one specific listitem is
sent as a parameter.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Here
are some of the relevant
lines of code in the
procedure being
executed.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">
if Item <> nil
then</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">
begin</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> if
Item.Selected then
UpdateButtons;</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">
…</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> Item.ImageIndex
:= 8;</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">
end;</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">There
are no deletions in the
procedure.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">The
Item.Selected test works
fine but Item.ImageIndex
:= 8 crashes at
TListItem.SetImage with
an access violation.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">The
item existed and then no
items exist based on the
screen shot.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">I’ve
been having to put
validations all over the
place like this…</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">if
ListView.Items.IndexOf(Item)
>= 0 then
Listitem.ImageIndex :=
8.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">This
user has had a crash
where it does this
validation up the
procedure somewhere
which validated, but
further down it will be
accessing Item.Index and
this crashes.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">It’s
a nightmare. I’m
wondering if it could be
corrupt RAM in the PC or
something.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Cheers,</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D">Ross.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<div
style="border:none;border-top:solid
windowtext
1.0pt;padding:3.0pt 0cm
0cm
0cm;border-color:rgb(181,
196, 223)
-moz-use-text-color
-moz-use-text-color">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a
moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz" target="_blank">delphi-bounces@listserver.123.net.nz</a>
[<a
moz-do-not-send="true"
href="mailto:delphi-bounces@listserver.123.net.nz" target="_blank">mailto:delphi-bounces@listserver.123.net.nz</a>]
<b>On Behalf Of </b>Kyley
Harris<br>
<b>Sent:</b> Tuesday,
9 April 2013 10:33
p.m.<br>
<b>To:</b> NZ Borland
Developers Group -
Delphi List<br>
<b>Subject:</b> Re:
[DUG] TListitems
disappearing and
reappearing causing
access violations</span><o:p></o:p></p>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<div>
<div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt">without
seeing the 10lines
above, and whats
inbetween (if you
were being literal)
its very hard to
say. <o:p></o:p></p>
</div>
<div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt">The only time I've ever had something
dissapear from a
list is when I
deleted it though
a callback,
method, thread
etc.. or freeing
something. <o:p></o:p></p>
</div>
</div>
</div>
<div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt">what
version of delphi is
the code now? How
does the list get
populated or edited
by the application..
<o:p></o:p></p>
</div>
</div>
</div>
<div>
<div>
<p class="MsoNormal">I'd
start by looking at
how many locations of
code insert or delete
the list items, and
verify none are being
called while your
procedure is executing
its for-loop,
(assuming the access
violation is an index
based one because of
the list count change)<o:p></o:p></p>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt"> <o:p></o:p></p>
</div>
</div>
</div>
</div>
<div>
<div>
<div>
<p class="MsoNormal"
style="margin-bottom:12.0pt"> <o:p></o:p></p>
<div>
<p class="MsoNormal">On
Tue, Apr 9, 2013 at
10:21 PM, Ross Levis
<<a
moz-do-not-send="true"
href="mailto:ross@stationplaylist.com" target="_blank">ross@stationplaylist.com</a>>
wrote:<o:p></o:p></p>
<div>
<div>
<p
class="MsoNormal">Wondering
if anyone has
any ideas.<o:p></o:p></p>
<p
class="MsoNormal"> <o:p></o:p></p>
<p
class="MsoNormal">I've
had this problem
a long time from
when I started
writing an app
about 7 or 8
years ago, but
it happens so
rarely it's not
usually an
issue. But one
user in
particularly is
regularly
sending me
MadExcept
reports which
either have
access violation
errors or "the
application
appears to be
frozen". In all
cases it's
during an access
of a TListItem
which was
perfectly valid
10 lines of code
up a procedure
but suddenly
doesn't exist.<o:p></o:p></p>
<p
class="MsoNormal"> <o:p></o:p></p>
<p
class="MsoNormal">The
screenshot
created at the
same time shows
the ListView has
no visible
items, but I
know for a fact
there are 30 or
more items in
the list. I
believe
sometimes the
items visually
disappear and
reappear shortly
afterwards, like
a Desktop
refresh.<o:p></o:p></p>
<p
class="MsoNormal"> <o:p></o:p></p>
<p
class="MsoNormal">I
think I've heard
something about
Windows
recreating the
window handles
or some such
thing. I don't
understand why
it would do so.
There are no
changes to the
listview that
would require
re-creating the
window.<o:p></o:p></p>
<p
class="MsoNormal"> <o:p></o:p></p>
<p
class="MsoNormal">Any
ideas?<o:p></o:p></p>
<p
class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><br>
_______________________________________________<br>
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Developers Group -
Delphi mailing list<br>
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</div>
<p class="MsoNormal"><br>
<br clear="all">
<br>
-- <br>
Kyley Harris<br>
Harris Software<br>
+64-21-671-821 <o:p></o:p></p>
</div>
</div>
</div>
</div>
</div>
<p class="MsoNormal"><br>
_______________________________________________<br>
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Delphi mailing list<br>
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</div>
<p class="MsoNormal"><br>
<br clear="all">
<br>
-- <br>
Kyley Harris<br>
Harris Software<br>
+64-21-671-821 <o:p></o:p></p>
</div>
</div>
</div>
</div>
</div>
<p class="MsoNormal"><br>
_______________________________________________<br>
NZ Borland Developers Group - Delphi mailing
list<br>
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</div>
<p class="MsoNormal"><br>
<br clear="all">
<br>
-- <br>
Kyley Harris<br>
Harris Software<br>
+64-21-671-821 <o:p></o:p></p>
</div>
</div>
</div>
</div>
</div>
<p class="MsoNormal"><br>
_______________________________________________<br>
NZ Borland Developers Group - Delphi mailing list<br>
Post: <a moz-do-not-send="true"
href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><br>
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with Subject: unsubscribe<o:p></o:p></p>
</div>
<p class="MsoNormal"><br>
<br clear="all">
<br>
-- <br>
Kyley Harris<br>
Harris Software<br>
+64-21-671-821 <o:p></o:p></p>
</div>
<pre> <o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>NZ Borland Developers Group - Delphi mailing list<o:p></o:p></pre>
<pre>Post: <a moz-do-not-send="true" href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><o:p></o:p></pre>
<pre>Admin: <a moz-do-not-send="true" href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><o:p></o:p></pre>
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<p class="MsoNormal" style="margin-bottom:12.0pt"> <o:p></o:p></p>
<div>
<p class="MsoNormal">-- <br>
<i>Fortune</i> favours the <b>brave</b><o:p></o:p></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br>
<o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>NZ Borland Developers Group - Delphi mailing list<o:p></o:p></pre>
<pre>Post: <a moz-do-not-send="true" href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a><o:p></o:p></pre>
<pre>Admin: <a moz-do-not-send="true" href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a><o:p></o:p></pre>
<pre>Unsubscribe: send an email to <a moz-do-not-send="true" href="mailto:delphi-request@listserver.123.net.nz">delphi-request@listserver.123.net.nz</a> with Subject: unsubscribe<o:p></o:p></pre>
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NZ Borland Developers Group - Delphi mailing list
Post: <a class="moz-txt-link-abbreviated" href="mailto:delphi@listserver.123.net.nz">delphi@listserver.123.net.nz</a>
Admin: <a class="moz-txt-link-freetext" href="http://delphi.org.nz/mailman/listinfo/delphi">http://delphi.org.nz/mailman/listinfo/delphi</a>
Unsubscribe: send an email to <a class="moz-txt-link-abbreviated" href="mailto:delphi-request@listserver.123.net.nz">delphi-request@listserver.123.net.nz</a> with Subject: unsubscribe</pre>
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