Hi John ,
These are life cycle methods .
- init()
Initializes the element instance after creation.
Applications must not call this hook method directly, it is called by the framework while the constructor of an element is executed.
Subclasses of Element should override this hook to implement any necessary initialization.
- onBeforeRendering()
Function is called before the rendering of the control is started.
Applications must not call this hook method directly, it is called by the framework.
Subclasses of Control should override this hook to implement any necessary actions before the rendering.
- onAfterRendering()
Function is called when the rendering of the control is completed.
Applications must not call this hook method directly, it is called by the framework.
Subclasses of Control should override this hook to implement any necessary actions after the rendering.
- exit()
Cleans up the element instance before destruction.
Applications must not call this hook method directly, it is called by the framework when the element is destroyed.
Subclasses of Element should override this hook to implement any necessary cleanup.
Once Page is navigated for first time then Page is created and above life cycle method are called .When navigation happens to second page then first page is not destroyed ( First page will be cached and In UI , it will be hidden ). So when comes back to first page again then new page is not created ( First Page visibility will be changed and Second Page will be hidden ) .
It is similar behavior of jQuery Mobile https://jquerymobile.com/
Regards,
Jibin Joy