How can I implement Paging library 2 Boundary Callback using Coroutines?

Question

I want to implement my custom PagedList.BoundaryCallback with coroutines, liveData and repository pattern using Paging Library 2, but I couldn't find a good example of integration of these libraries.

Even in Android official samples, they use enqueue and callbacks to perform the API request with paging 2...

I read this Medium post also but it use a coroutines scope inside the boundary callback and I think that is not a good practice.

Is there any way to achieve it? Or should I migrate to Paging 3?

Answer 1

This solution works for me:

1. I injected a CoroutinesDispatcherProvider in my Repository:

   class MyRepository @Inject constructor(
       private val remoteDataSource: MyRemoteDataSource,
       private val localDataSource: MyDao,
       private val coroutinesDispatcherProvider: CoroutinesDispatcherProvider
    ) {...}
   

2. Then inside my repository, I passed this provider to my boundary callback:

   private val boundaryCallback =
       MyBoundaryCallback(remoteDataSource, localDataSource, coroutinesDispatcherProvider)
   
   fun getList(): LiveData<PagedList<MyModel>> = LivePagedListBuilder(
       localDataSource.getAll(),
       pagedListConfig
   ).setBoundaryCallback(boundaryCallback).build()
   

3. And finally, I use this dispatcher in my boundary implementation to launch my request from repository:

   private val ioCoroutineScope by lazy {
      CoroutineScope(coroutinesDispatcherProvider.io)
   }
   
   override fun onZeroItemsLoaded() {
       ioCoroutineScope.launch {
           remoteDataSource.getList()
       }
   }