appbar - Windows Phone 8.1 BottomAppBar disappeared after resuming or navigating to another page -

i have bottomappbar declared in xaml 1 listpage , bottomappbar in reportspage. when app resuming bottomappbar disappeared , it's disappeared when i'm navigating listpage reportspage using messagedialog control.

listpage:

<page.bottomappbar>     <commandbar x:name="bottomapplicationbar" loaded="frameworkelement_onloaded">         <appbarbutton x:name="addappbarbutton" isenabled="true" label="{binding [select_button], source={staticresource localizedstrings}}" icon="edit" />         <appbarbutton x:name="refreshappbarbutton" isenabled="true" label="{binding [refresh_button],source={staticresource localizedstrings}}" icon="refresh" />         <appbarbutton isenabled="false" x:name="settriptypebarbutton" label="{binding [triplist_bulkedit_set_trip_class], source={staticresource localizedstrings}}" visibility="collapsed"  flyout="{staticresource triptypeflyout}">             <appbarbutton.icon>                 <fonticon glyph="t" fontweight="bold"/>             </appbarbutton.icon>         </appbarbutton>         <appbarbutton isenabled="false" x:name="settrippurposebarbutton" label="{binding [triplist_bulkedit_set_purpose], source={staticresource localizedstrings}}" visibility="collapsed" >             <appbarbutton.icon>                 <fonticon glyph="p" fontweight="bold"/>             </appbarbutton.icon>         </appbarbutton>         <appbarbutton isenabled="false" x:name="deleteappbaritem" label="{binding [triplist_bulkedit_delete], source={staticresource localizedstrings}}" icon="delete" ></appbarbutton>         <commandbar.secondarycommands>             <appbarbutton visibility="collapsed" x:name="alltripsbutton"  label="{binding [triplist_bulkedit_all_trips],source={staticresource localizedstrings}}" icon="font" />                             <appbarbutton visibility="collapsed" x:name="alltripspurposebutton" label="{binding [triplist_bulkedit_missing_purpose], source={staticresource localizedstrings}}" />             <appbarbutton visibility="collapsed" x:name="alltripsfromreportbutton" label="{binding [triplist_bulkedit_all_trips],source={staticresource localizedstrings}}"   />         </commandbar.secondarycommands>     </commandbar> </page.bottomappbar>      

reportspage:

<page.bottomappbar>     <commandbar x:name="submitappbar" isopen="true" >         <commandbar.primarycommands>                            <appbarbutton x:name="submitreportappbarbutton" label="{binding [report_submission_submit_button], source={staticresource localizedstrings}}" click="submitreportappbarbutton_onclick" icon="accept" isenabled="false" />         </commandbar.primarycommands>     </commandbar> </page.bottomappbar>