ScrollView vs RecyclerView for dissimilar children on Android

Question

I have a mix of 10-15 custom views and fragments to be shown in a vertical list. I am not sure if RecyclerView has any advantage in scenarios where all views are dissimilar. RecyclerView seems to add lot of boiler-plate code, and I think the only advantage I would get is easier enter/exit animation.

My custom views/fragment also make web-service call on being created. We don't cache web-requests for business reasons. My understanding is that RecyclerView would trigger these web-service calls on each binding, resulting in redundant calls and visible latency. Comparatively ScrollView should load the views once, and it keeps them all in memory, avoiding multiple calls.

Is my understanding correct ? I need some help understanding performance implications with ScrollViews, in the given scenario.

Answer 1

ScrollView

With a ScrollView, all of its subviews will be created at once, regardless of visibility on screen. If using a ScrollView for your solution, you'll probably want to "listen" for when its subviews become visible to update their content, using placeholders initially. You could also build something that will fetch the content in a background thread. This may get more complex than you want very quickly.

RecyclerView

A RecyclerView provides the advantage of deferring creation of child views until they become visible automatically, and can re-use child views with common layouts.

By using different "item view types" for each of your children, you'll disable the "recycling" part of RecyclerView, but still get the benefit of deferring the creation of views until they are scrolled into view.

RecyclerViews do provide a fairly structured pattern for you to work with via the Adapter and ViewHolders. Though not personally familiar with it, RecyclerView also has a RecyclerView.ViewCacheExtension which is intended to give the developer control over caching of views.

Overall, the advantage of late binding (don't create and load views that might never be viewed) and the flexibility of the RecyclerView will probably yield good results for you.

Answer 2

First of all you have to decide what you are using View or Fragment or maybe both. Don't compare View with Fragment there is a common misconception about these two, they are not similar, actually a Fragment is close to an Activity in terms of architecture and implementation.

Second, can you reuse some of these View/Fragment, if yes, then RecycleView can help you a lot.

After you decided about the topics above:

My understanding is that RecyclerView would trigger these web-service calls on each binding

No, this is not true, the binding method is called whenever a new item is displayed (reused or newly created), you can implement adapter to perform the web API only once on an item, this is your choice.

I always go for RecycleView/ListView whenever possible, it helps to reduce the memory footprint and can reduce the implementation. In some cases, where there is no huge memory usage on views and I can't reuse some of the implementation, then I go for ScrollView, but I think twice before implementing it.