Hello,

I am using a tabbox with mvvm (see example zul), to group editable parameters for a stored process that can be started via web ui.

When I edit a textbox inside a tabpanel and immediately click on another tab (without leaving the textbox first), I get a NullPointerException (stracktrace included).
The reason seems to be that the Tab component receives an AuRequest that does not include the selected Tab. Furthermore, the Tab does not have access to its _parent (via AbstractComponent), which is null in this case.

I tried to circumvent the issue by adding a before-expression in the textbox definition (see example zul), but it has no effect.

Is there a way to solve this issue without changing the ZK sourcecode?

Many thanks in advance,
Johannes

Example 1:
{{ <tabbox id="mainTabbox" vflex="1" height="100%"
visible="@load(vm.paramGridIsVisible)" orient="bottom">
<tabs id="subTabs"
children="@bind(vm.paramGroupTab) @template('pgrouptemplate')"
width="200px">
<template name="pgrouptemplate" var="pgroup">
<tab label="@load(pgroup.name)"
selected="@load(vm.pickedItem eq pgroup)"
onSelect="@command('onParamGroupTabSelect',item=pgroup)"
tooltiptext="@load(pgroup.footnote)" />
</template>
</tabs>
<tabpanels id="subTabpanels" vflex="1"
children="@bind(vm.paramGroupTab) @template('pgrouppaneltemplate')">
<template name="pgrouppaneltemplate" var="pgroup">
<tabpanel>
<borderlayout style="background:white">
<center border="none" autoscroll="true">
<grid vflex="1"
model="@load(pgroup.params) @template( each.paramName eq 'separator'?'spacertemplate':each.templateName)">
<columns>
<column hflex="1"
label="${labels.lblParamName}" />
<column hflex="2"
label="${labels.lblParamValue}" />
</columns>
<template name="textboxtemplate"
var="visibleParam">
<row
tooltiptext="@load(visibleParam.paramHelpText)">
<label
value="@load(visibleParam.paramName)" />
<cell>
<textbox hflex="1"
value="@load(visibleParam.displayValue) @save(visibleParam.paramValue, before=

{'onStartClick','onParamGroupTabSelect'}

)"
constraint="${w:newParamInputConstraint(visibleParam)}"
disabled="@load(visibleParam.isReadOnly)"
onChange="@command('onChangeParam',param=visibleParam)"
focus="@bind(visibleParam.selected)" />
</cell>
</row>
</template>
<!-- more template definitions, omitted for brevity -->
</grid>
</center>
<south border="none">
<checkbox
label="${labels.lblParamSaveUserSettings}"
visible="@load(pgroup.saveUserSettingsIsVisible)"
checked="@load(pgroup.saveUserSettingsIsChecked)"
onCheck="@command('onCheckSaveUserSettings',group=pgroup, checked=self.checked)" />
</south>
</borderlayout>
</tabpanel>
</template>
</tabpanels>
</tabbox>
}}

Stacktrace:
{{Mai 03, 2017 10:43:27 AM org.zkoss.zk.ui.impl.UiEngineImpl handleError
SCHWERWIEGEND:
java.lang.NullPointerException
at org.zkoss.zul.Tab.service(Tab.java:404)
at org.zkoss.zk.ui.impl.DesktopImpl.service(DesktopImpl.java:710)
at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1249)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.process(DHtmlUpdateServlet.java:603)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.doGet(DHtmlUpdateServlet.java:485)
at org.zkoss.zk.au.http.DHtmlUpdateServlet.doPost(DHtmlUpdateServlet.java:494)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
}}