android-paging | Jetpack Paging codelab | Model View Controller library

Following this codelab I have implemented pagination and caching using RemoteMediator (I am calling a simple API that returns a list of news). I am injecting this RemoteMediator to Repository which has method getResultStream() that returns Flow>. In ViewModel is function getNews() : Flow> and in Fragment I am calling this function and submitting list to RecyclerAdapter.

Now I want to add a new API call that returns news but with search keyword. What is the proper way to do it? Do I have to write all this code again and create a new RemoteMediator? The logic will be the same but now I have to pass a string argument to the Retrofit get function. The result of this call will replace items in RecyclerView, so I will have two sources of data but one Recycler, do I have to create also a MediatorLiveData? (I don't add any code but if it help I can do it)

One person asked how exactly I did it (Question posted as answer so it is deleted now but maybe it will help someone in future). So, in ViewModel I have this:

After making a simple app with Paging 3 (based on this Google GitHub codelab) my app crashes. When I scroll down, at some point (probably when the new GET function is called). Logcat looks like this:

How to convert this Kotlin class to Java

set span size to 1 in GridLayoutManager when LoadState is Loading in Paging Library. I have tried this solution but it's not working.

For replicate issue: clone this official repo and set GridLayoutManager in SearchRepositoriesActivity

My code is here

MovieListFragment

Is background threading managed automatically with PagingData as it is with PagedList, and then returned on the main thread?

From the logs below, it appears PagingData is not run on the backgroud thread in the Paging 3 library compared to PagedList in Paging 2's library.

Expect (Based on the Paging Codelab sample)

• GithubPagingSource override suspend fun load(...) to run on an IO thread.
• SearchRepositoriesActivity viewModel.searchRepo(query).collectLatest { ... } to run on the main thread.

Observe

• Both GithubPagingSource override suspend fun load(...) and SearchRepositoriesActivity viewModel.searchRepo(query).collectLatest { ... } run on the main thread.

Threading is handled on the background by PagedList with toLiveData according to the documentation.

If you use LivePagedListBuilder to get a LiveData, it will initialize PagedLists on a background thread for you.

The Paging 3 documentation does not mention how threading is managed. However, from the logs, PagingSource appears to be running the network request on a main thread and returning the PagingData on a main thread.

I've recreated the Codelab pattern in the CryptoTweets sample app app-simple module.

FeedPagingSource.kt

I'm currently using Google's Paging3 library for the first time. I'm basing my code on their Codelab at https://codelabs.developers.google.com/codelabs/android-paging/#0.

The flow of my app adheres to the following rules:

1. display empty state
2. let users search for something
3. display results
4. when user presses back button on searchbar -> display empty state again

The codelab unfortunately does not deal with empty states :( I'm using the following addLoadStateListener to deal with the search results:

I was trying to imitate Google's codelab for the new Paging 3 library, and I encountered the following error when I tried to have a Room DAO method return a PagingSource:

Suppose I have a API resource that displays a list of animals, let's call it /animals, and I have another that is used to search the list of animals using their species, /animals/{species}, if I were to use Android's new Paging3 library, would I have to create two separate PagingSourceobjects for them? The Codelab for paging has one class that extends PagingSource called GithubPagingSource, but it is only for one endpoint. I was wondering what the correct approach would be.

Im trying to implement Paging but every time i rotate a screen constructor of view model gets called, thus triggering loadInitial to fetch new data from network in my DataSource class.Help appreciated