Does RecyclerView.ViewHolder always have to be an inner class?

Question

I have two RecyclerView.Adapters that are using exactly the same RecyclerView.ViewHolders as inner classes.

I wanted to get rid of code duplication and made these ViewHolders free, separate class so the brand new class now can be used by any RecyclerView.Adapters.

However I faced lots of troubles for example difficulty in accessing the adapter objects. getAdapterPosition() always returns -1.

So I changed my mind and made a super RecyclerView.Adapter class which is extended by those adapters and put the ViewHolder in the superclass so those adapters can use it from subclass.

But I want to know if ViewHolder does have to be an inner class. This makes me annoyed. Please do NOT advice me to combine the Adapter classes, they are completely different as the ViewHolder is just a special viewType that can be appear in any RecyclerView

I am waiting for your better approaches which make me feel better.

Regards.

Answer 1

ViewHolder can be outside class. Inner class is only a proposition in all tutorials for RecyclerView, it is a better way if your ViewHolder should have access to all Adapter parameters, even those private, but any access or objects relations can be recreated by access methods in Adapter and ViewHolder.

I have created stand alone project with usage of ViewHolder as an outside class, take a look. Link to repository - https://github.com/maciejsikora/outsideviewholder.

I think also the cause of your problem is the fact that in the first code version ViewHolder was an inner class and had access to the properties, after change into an outside class, the code should have been refactored, and in the result all relations between ViewHolder and Adapter should be deeply checked.

Answer for the question is - ViewHolder doesn't have to be inner class, and your problems are caused by invalid code implementation in using ViewHolder as an outside class.

Answer 2

Actually, No.

First you need to understand that why we need Inner class?

We do need Inner classes where we want that only particular class will have this functionality.Like we have many inner class for many Listeners and Button onClick and many more.

So we use inner class for making things private,short and simple .

You can make this thing(ViewHolder) a separate class.But that will not be efficient,clear(If you make another class it will add an extra class to your project),and effective way.