I am developing a Sencha touch 2 app where I want to detect when the user navigates from one page to another. I want to call a function just like "onunload" in javascript. Any suggestions? Thanks in advance.
That depends on the way you are implementing your navigation.
1. NavigationView
http://docs.sencha.com/touch/2.3.1/#!/api/Ext.navigation.View
The NavigationView is a card based layout where you can pop or push views.
There are events like activeitemchange, pop, push etc.
You can add these events as listener to your component
Example: listeners : { pop : function(cmp, view, eOpts) {
...
}
}
2. Container Navigation
You can create a card based container and add/remove the views from this container.
There you are able to use the activeitemchange, add and remove event.
But in both cases its mostly the same. You have to set a listener with the event to the outer container (where your views are inside). There you can define your action for switches of views