how to get reference to sap.m.App?

Dear Guys,

I create a master view in which i put such code:

<mvc:View xmlns:mvc="sap.ui.core.mvc"  xmlns:custom="http://schemas.sap.com/sapui5/extension/sap.ui.core.CustomData/1"  xmlns="sap.m">  <App id="myApp">  </App></mvc:View>

I take this view as a base view from which I can nav to full screen views and split containers.

while how can i get the reference to "myApp" in other controller? I tried :

sap.ui.getCore().byId("myApp")

but not work.

Very appreciated if someone give me a hint.

Thanks,

Leon