SplitApp with PageHeader and SubHeader

Hi,

I try to create a SplitApp with Page Header and SubHeader like:

<mvc:View height="100%"
   controllerName="com.xxx.n4c.Activities"
   xmlns:mvc="sap.ui.core.mvc"
   xmlns:l="sap.ui.layout"
   xmlns:core="sap.ui.core"
   xmlns="sap.m">

   <Page  showHeader="true"

   enableScrolling="false" >

   <customHeader>

   <Bar>

   <contentLeft>

   <Image src="img/logo.png"></Image>

   </contentLeft>

   <contentMiddle>

   <Label text="Aktivitäten bei:"></Label>

   <Label text="{NAME1}"></Label>

   </contentMiddle>

   </Bar>

   </customHeader>

   <subHeader>

   <Bar>

   <contentLeft>

   <Button icon="sap-icon://list" text="Kundenliste" press="goList"></Button>

   <Button icon="sap-icon://business-by-design" text="Kundenmenü" press="goBack"></Button>

   </contentLeft>

   </Bar>

   </subHeader>

   <SplitApp id="SplitAppDemo" initialDetail="detail" initialMaster="master" mode="PopoverMode">

   <masterPages>

   <Page id="master" icon="sap-icon://action"  enableScrolling="true" showHeader="true" title="Aktivitäten">

....

Works fine.

The problem is, that the MasterView lost its reponsibility. When I rund the code on a smartphone I only see the DetailView. MasterView is hidden. No Button to open it as popover is shown.

Any Ideas, how I can proceed?

Cheers

Jens