RealmPagination

Just a copy of Google Paging library (https://developer.android.com/topic/libraries/architecture/paging) entirely rewritten in Kotlin and intended to be used with Realm.

Adding to project

To use RealmPagination you need to add as a dependency:

implementation 'com.github.magora-android:realmpagination:1.0.0'

And it's available on Jitpack, so you need to add

allprojects {
    repositories {
        // ...
        maven { url "https://jitpack.io" }
    }
    // ...
}

How To

First you need to create a DataSourceFactory

class UsersListDataSourceFactory : RealmDataSource.Factory<Int, User>() {

    override fun create(): RealmDataSource<Int, User> {
        val result = object : RealmPageKeyedDataSource<Int, User>() {
            override fun loadInitial(params: LoadInitialParams<Int>, callback: LoadInitialCallback<Int, User>) {
                //...
            }

            override fun loadBefore(params: LoadParams<Int>, callback: LoadCallback<Int, User>) {
                callback.onResult(0, null)
            }

			override fun loadAfter(params: LoadParams<Int>, callback: LoadCallback<Int, User>) {
                //...
            }
        }
        return result
    }

    override fun destroy() {
        //...
    }
}

val dsFactory = UsersListDataSourceFactory()

Then you need to create a Paged List

private const val INITIAL_PAGE_SIZE = 50
private const val PAGE_SIZE = 30
private const val PREFETCH_DISTANCE = 10

val config = RealmPagedList.Config.Builder()
                .setInitialLoadSizeHint(INITIAL_PAGE_SIZE)
                .setPageSize(PAGE_SIZE)
                .setPrefetchDistance(PREFETCH_DISTANCE)
                .build()

val pagedList = RealmPagedListBuilder(dsFactory, config)
                .setInitialLoadKey(0)
                .setRealmData(localStorage.getUsers())
                .build()

Then create an adapter

class AdapterUserList(data: RealmPagedList<*, User>) : BaseRealmListenableAdapter<User, RecyclerView.ViewHolder>(data) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        //...
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        //...
    }
}

val adapter = AdapterUserList(pagedList)
usersList.adapter = adapter

... and use the power of pagination