This sample demonstrates how to use the Paging library with a backend API (in this case Reddit API).

There are 3 variations of the demo, which you can select in the MainActivity class.

After selecting an option, it starts the RedditActivity which is the activity that shows the list of posts in a given subreddit.

This sample, implemented in the DbRedditPostRepository class, demonstrates how to set up a Repository that will use the local database to page in data for the UI and also back-fill the database from the network as the user reaches to the end of the data in the database.

It uses Room to create the PagingSource (dao). The Pager creates a stream of data from the PagingSource to the UI, and more data is paged in as it is consumed.

This usually provides the best user experience as the cached content is always available on the device and the user will still have a good experience even if the network is slow / unavailable.

This sample, implemented in the InMemoryByItemRepository class, demonstrates how to set up a Repository that will directly page in from the network and will use the key from the previous item to find the request parameters for the next page.

ItemKeyedSubredditPagingSource: The data source that uses the key in items (name in Reddit API) to find the next page. It extends from the PagingSource class in the Paging Library.

This sample, implemented in the InMemoryByPageKeyRepository class, demonstrates how to utilize the before and after keys in the response to discover the next page. (This is the intended use of the Reddit API but this sample still provides ItemKeyedSubredditPagingSource to serve as an example if the backend does not provide before/after links)

PageKeyedSubredditPagingSource: The data source that uses the after and before fields in the API request response. It extends from the PagingSource class in the Paging Library.

• Android Support Library
• Android Architecture Components
• Retrofit for REST api communication
• Glide for image loading
• espresso for UI tests
• mockito for mocking in tests
• Retrofit Mock for creating a fake API implementation for tests