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https://issues.apache.org/jira/browse/WICKET-6045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15028697#comment-15028697
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Tero Tarkkala commented on WICKET-6045:
---------------------------------------
Yes, forgot to mention we have set a viewsize. And since that is set after
construction, the null list works when constructing. Yes, I could check if my
list is null and replace it with an empty list (this is actually what I do now)
or set the viewsize to zero, but is there a reason for this strange if-clause
in the getViewSize()? If it would return zero when the modelObject is null,
this would work without the extra checks for null lists. Also, having a null
list and then setting a viewsize wouldn't accomplish anything useful.
> ListView gets wrong viewsize when changing from arbitrary list with size > 0
> to null list
> -----------------------------------------------------------------------------------------
>
> Key: WICKET-6045
> URL: https://issues.apache.org/jira/browse/WICKET-6045
> Project: Wicket
> Issue Type: Bug
> Affects Versions: 7.1.0
> Reporter: Tero Tarkkala
> Assignee: Sven Meier
> Priority: Minor
>
> ListView tries to render the null list because of the beginning of method
> ListView.getViewSize():
> public int getViewSize()
> {
> int size = viewSize;
> final Object modelObject = getDefaultModelObject();
> if (modelObject == null)
> {
> return size == Integer.MAX_VALUE ? 0 : size;
> }
> ....
> Let say I had 10 items in the list before a refresh to this listview. When
> refreshing, my getter returned null because it didn't find anything
> -> modelObject is null and size != Integer.MAX_VALUE
> -> previous viewSize is returned.
> -> populateItem throws npe if it tries for example getDefaultModelObject()
> like this:
> java.lang.NullPointerException
> at
> org.apache.wicket.markup.html.list.ListItemModel.getObject(ListItemModel.java:61)
> at org.apache.wicket.Component.getDefaultModelObject(Component.java:1626)
> at
> syncrontech.common.gate.list.GateEditableListPanel$2.populateItem(GateEditableListPanel.java:264)
> at
> org.apache.wicket.markup.html.list.ListView.onPopulate(ListView.java:523)
> The behaviour is also inconsistent: Constructing the listview with null list
> is ok, because that same point in code would return the 0.
> This should probably always return 0 if the modelObject is null? Or am I
> missing something?
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