Summary

This content provides a tutorial on implementing an infinite scrolling RecyclerView list using Paging 3 and Android Room Database, featuring a social media-like feed.

Abstract

The provided content is a detailed tutorial on creating an infinite scrolling RecyclerView list using Paging 3 and Android Room Database. The tutorial starts with an introduction to the idea of an infinite social media-like feed and mentions the required dependencies. It then proceeds with setting up the Android Room database, creating a UserPostEntity, and building a UserPostDao for saving new posts and querying random posts.

The tutorial further explores the Paging library, which is responsible for loading random posts in fixed chunks from the database, by creating a PagingSource. The PagingSource is then used to set up a ViewModel, which provides access to the paged random posts.

Finally, the tutorial guides you through setting up the UI, including creating a PagingDataAdapter, creating the layout, and integrating the UI components to display the retrieved random data. The tutorial concludes with a note on how to fill in some dummy data and use the infinite scrolling list.

Bullet points

Introduction to the idea of an infinite social media-like feed
Mention of required dependencies: Android Room, Paging 3, and RecyclerView
Setting up the Android Room database
Creating UserPostEntity and UserPostDao for saving new posts and querying random posts
Exploring Paging library and creating PagingSource for loading random posts in fixed chunks
Setting up ViewModel to provide access to the paged random posts
Creating PagingDataAdapter, creating the layout, and integrating UI components
Displaying retrieved random data in the UI
Conclusion with a note on filling in dummy data and using the infinite scrolling list

CODEX

Infinite RecyclerView List with Paging 3 And Android Room Database

Realize an infinite social media-like feed

You may know these infinite lists from e.g. your Pinterest, TikTok, or even your Instagram “explore” feed. It makes you want to scroll and scroll but unfortunately, you will never reach the end.

Features like these can really hook up your user, in terms like Nir Eyal describes in his famous book “Hooked — How to Build Habit-Forming Products”.

Today I will show you how you can easily achieve an infinite scrolling list for a RecyclerView with a combination of Android Room and Paging 3.

To follow along with this article, as the only requirement you should know how to set up a database with Android Room.

The Idea

Coming back to the examples from the introduction. As you scroll through your social media feed, random posts, mostly based on your interests, will appear over and over again.

For this article, we leave the interest-based part aside and concentrate on the random querying of text-based posts from our database. We accept within this approach that duplicates can appear.

Dependencies

Like already mentioned, we will make use of Android Room, Paging 3, and RecyclerView. If you managed to add all of the required dependencies, your app-level build.gradle should look somewhat like the following:

Android Room

For the database part, we use one simple Entity called UserPostEntity . The entity just contains an auto-incrementing idcolumn and also one for the textof the respective post.

Next, we create our respective data access object (DAO). When you implement it, you should also add the respective functions for saving new posts so you can later add dummy data. The UserPostDao should also contain the following getRandomPosts(size: Int)function:

The query for this function makes use of the SQLite function for generating random values. All entries, limited by the transmitted size get ordered by their respective random value. Afterward, only posts from this random selection get selected and returned. The size parameter will later be set by our PagingConfig .

Note: For a proper implementation you would also create a respective repository, use dependency injection, and so on. For the sake of clarity, we skip these parts and only concentrate on the relevant components.

Paging 3

The Paging library will be responsible for loading random posts in fixed chunks from our database. To make use of this feature we first have to create a PagingSource .

As you can see as a parameter we have our DAO so we can retrieve the random posts right from our PagingSource . For the size parameter, we put in the params.loadSize which will later be defined within the PagingConfig .

Because the load function is already a suspend function, we don’t need to create an extra coroutine scope or retrieve a scope via the constructor for the database access.

We are just emulating our pages because we rely on randomly queried data. Therefore, we set the prevKey and also the nextKey by decrementing and respectively incrementing the current position by one.

Because we randomly query our data we have no real position we could go back to. So for the refresh key, that is returned in the getRefreshKey()function, we just return null.

The ViewModel

The ViewModel will later be used by the UI to access the paged random posts. Here we set up our PagingSource and provide it for the respective accessors.

The MainViewModel is rather pseudo-code, you would want to retrieve the actual data via a proper architecture structure and also make use of dependency injection.

The main point I want to show you here is how to build up your Flow that you will later retrieve from your UI part. We create a new Pager that gets a PagingConfig object. The 10 in the constructor stands for the item size of each page. In this case, when the database returns less than 10 items, it will assume that there are no more items left to be retrieved.

Because we have no end with our random generation of posts, we will retrieve posts until infinity (or until our RAM is full lol).

For the pagingSourceFactory parameter we set a new object of our PagingSourceand put into our DAO.

In Line 4 we transform the PagingSource to a Flowand cache the PagingData within our ViewModelScope.

Set up the UI

As the last part of the puzzle, we build and integrate the UI. Here we will now connect the parts we previously set up and show the retrieved random data to our user.

PagingDataAdapter

As the first step, we need to create an adapter that we later assign to our RecyclerView.

Creating the layout

First, create a simple layout containing a RecyclerView.

Next, create the respective Activity:

Here you can see that we set initialize our RecyclerView with the UserPostsPagignAdapter and a LinearLayoutManager. We then just collect the Flow of random posts from our ViewModel and set the source to our adapter.

Conclusion

Within this article, we took a look at a combination of Android Room, RecyclerView, and Paging 3 to build an infinite scrolling list that can be used for example for implementing a social media feed.

After following the steps from above and adapting the code snippets to your architecture, you just need to fill in some dummy data and are ready to use your infinite scrolling list.

I hope you had some takeaways, clap if you liked my article, and follow for more!

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