Button remove when you click on second tab and back - sapui5

Question

Im using the following code to display simple button,when you click on tab 2 and return to the old tab the button is removed,any idea how do put it permanent in tab1 ?
This is the controller shell
onInit: function() {
this.oViewBuffer ={};
this.oViewBuffer.btn = sap.ui.jsview("codetalk.Main");
var oShell = sap.ui.getCore().byId("main-shell");
oShell.setContent(this.oViewBuffer.btn);
},
onWorksetItemSelected:function(oEvent){
var oShell = sap.ui.getCore().byId("main-shell");
var key = oEvent.getParameter("key");
oShell.setContent(this.oViewBuffer[key]);
}
This is the JS view
createContent : function(oController) {
var oButton = new sap.ui.commons.Button({
text:"Hello Test",
tooltip:"This is toolTip",
press:function(){
alert("test alert");
}
});
return oButton;
}
This is the view of the shell
createContent : function(oController) {
var oButton = new sap.ui.ux3.NavigationItem({
key:"bth",
text:"Tab 1"
});
var oMusicStore = new sap.ui.ux3.NavigationItem({
key:"btn2",
text:"Tab 2"
});
var oShell = new sap.ui.ux3.Shell({
id:"main-shell",
appTitle:"Demo",
worksetItems:[oButton,oMusicStore],
worksetItemSelected:[oController.onWorksetItemSelected,oController]
});
return oShell;
}

Answer 1

first I'd recommend removing the "-" in your shell id (UI5 Dev Guide) and using camel case instead.
secondly you're calling your view with your button in the Init function but once that's done you handle your worksetItems with your controller and set the worksetItem according to your key. So far so good.
But your worksetItems aren't associated with any content so there's no reason for your shell to show you the button when you click on your first Tab
I'd recommend something like initializing your views with IDs and ste the content in your shell controller according to that id
Example:
var oViewButton = sap.ui.view("bth",{
viewName : "codetalk.Main",
type : sap.ui.core.mvc.ViewType.JS
)} //do that in your view where you define your Shell
//do the same for your view with the musicstore also in the view with the Shell
//your id of the view must match the key of your worksetItem
in your shell's controller do this:
onWorksetItemSelected : function(oEvent){
var oShell = sap.ui.getCore().byId("mainShell");
var key = oEvent.getParameter("key");
var oView = sap.ui.getCore().byId(key);
oShell.setContent(oView);
}
this solution will bypass the content aggregation of your Shell but at least it worked for me.

Answer 2

In shell view.js remove second last line
Example
"worksetItemSelected:[oController.onWorksetItemSelected,oController]"
It might work