Xamarin Forms uses a very neat and simplified Navigation Architecture which can be easily justified among Android, iOS and WinPhone mobile platforms under common grounds.
Xamarin Forms Navigation
Alright, now this is not an article about Xamarin Forms Navigation article, as it is very well explained in Xamarin official documentation. If you want to go check it out right now before you get into this article. https://developer.xamarin.com/guides/xamarin-forms/user-interface/navigation/hierarchical/
Now the way Xamarin Forms handles this navigation during the actual runtime, specifically in native levels are different for each mobile platforms. Of course they have to somehow map Xamarin Forms Navigation paradigm to the Native app navigation paradigm, which is extremely complex and Xamarin has done a great job so far. 😀
Why is Navigation so Important?
Navigation plays a huge part in your Mobile Application development, specially when it becomes more complex when you need to implement deeper customisations to your cross platform app.
So when we get down to complex customisations related to your Navigation, it is very important to be aware of the underlying mechanics of the platform.
Hence with Xamarin Forms, we are dealing with a cross-platform situation, where it is very crucial that we pay attention to three different mobile platforms, and how their navigation is actually handled in Xamarin Forms.
Xamarin has done a great job in handling a common cross-platform navigation pattern, and faded out the Native-compatibility mechanics to the background, to the point a developer doesn’t really have to pay any attention to it. So kudos Xamarin! 😉
So the reason I’m writing this article is because, recently I came across a situation where I had to pay detailed attention for Xamarin Forms Navigation and how it actually handles it in native execution. 🙂
And there’s something very interesting I spotted in how Xamarin Forms handles Navigation in Android runtime..
So I thought of sharing it with everyone, hence most developers doesn’t seem to be aware of this.
Specially amongst the fresh developers of the Xamarin Community, where a lot of developers assume Xamarin Forms follows everything exactly as the Native Framework patterns and properties, which is not actually accurate and they have taken some unique (or may be different) approaches for mapping Native stuff to the Xamarin Forms level, which are quite out of the box. So you need to pay a good attention to their details when you are dealing with complex implementations in Xamarin Forms.
So what’s the big deal I found with Xamarin Forms Navigation in Android ?
Xamarin Forms Navigation in Android?
Now when it comes to handling Xamarin Forms Navigation in Android run time, I noticed something very interesting, which I should blame myself for not paying any attention way earlier for this aspect. However…
If you’re familiar with Native Android development, the standard pattern of how we navigate in-between Activities and Fragments, how the activity lifecycle is handled so on and so forth yeah? (Nope, I’m not gonna get into the details of Android Navigation pattern in this article, if you aren’t aware, please stop reading this article and Google about it, then you may get back here… other wise you might get confused!)
Now have you ever thought how Xamarin Forms actually handles this complex Android Navigation Pattern? And actually map the Xamarin Forms Navigation paradigm to the Native Android Execution?
Now this is where it gets interesting…
Go on to this link which explains the NavigationPage (the page that manages the navigation) of Xamarin Forms, and read the REMARKS! READ IT!
Let me quote it,
“Note that on the Android platform, INavigation operations do not generate activity lifecycle notifications. For each Page that you push or pop, the Android implementation of NavigationPage simply adds or removes the content of the page to or from a single activity.”
Now I did some more research about it, and came across more interesting facts.
At Xamarin Evolve 2014…
Watch this Youtube clip where an attendee asks Jason Smith about the Navigation pattern of Xamarin Forms in Android.
Attendee: I was curious why you designed the Xamarin Forms Android to be a Single Activity as opposed to Multiple Activity?
Jason: Couple of minor considerations I guess. At the time Fragments weren’t fully back ported when we started the project. So we couldn’t actually target Fragments, which was really annoying. And Google was advocating the Single Activity approach and on top of that Navigations Paradigms of Activity didn’t fully map to the Xamarin Forms Navigation Paradigm.
Furthermore from Jason Smith…
So I found a post in Xamarin Forms Community Forum where Jason Smith has commented regarding the navigation further more a s follows…
“Xamarin.Forms pre-dates the backporting of Fragments on Android, however it is written in a fashion similar to how fragments work. The Views we add/remove from the view hierarchy are fully cleaned up and disposed of when they go away. This works around the standard issue people had with single activity apps where all the views would stick around eating lots of memory.
Even if you as the user pre-allocate all of your Xamarin.Forms views, we do not realize them into actually android objects until they are needed on screen. We then will remove and dispose those same objects dynamically when they are no longer needed. This means that you should not be paying a significant memory overhead, even if you are not mindful of this yourself.”
So now what does this all tell us?
So after all these findings what is the conclusion we could come to?
In Native Android Development…
When we develop Native Android application we usually use the standard Multiple Activities approach to propagate the pages and to navigate in between them, and sometimes we throw in some Fragments here and there as needed for memory saving and re-usability.
There is also an approach called “Single Activity Architecture” approach where you maintain only one activity and render all the pages on top of it in Native Android development.
Xamarin Forms Navigation in Android?
Short and sweet Xamarin Forms does not follow the same standard multiple activity pattern in Android
Xamarin Forms uses a unique Single Activity Architecture based pattern in Android which is similar to the use of Fragments, but with a better management of memory with its approach…
As with all our findings this is quite a unique approach that Xamarin Forms has implemented under the hood for Android. Which is very important to keep in mind when you get down to complex implementation of Xamarin Forms in Android.
Advantages and also Disadvantages ?
This gives many advantages and also disadvantages for us developers. Advantages such as good memory management, ease of navigation, instead of dealing with Activities and Fragments directly.
But this also brings many disadvantages which I had struggled in great deals with in Xamarin Forms complex implementations for Android, such as management of a custom ActionBar across your views, adding custom page transition animations for pages, unpleasant UX behavior when hiding ActionBar and so on.
But then again, there is always a way to solve problems in programming. 🙂
That’s it… 🙂
Well there you go, hope this clears any confusion anyone had just like I did sometime back… 🙂 And if you weren’t aware of this before, now you know how to handle stuff when it’s in need during your Xamarin Forms mobile development.