pagination-patterns

Pagination Patterns for Mobile

Dependencies (Android)

dependencies {
    val pagingVersion = "3.3.5"
    implementation("androidx.paging:paging-runtime-ktx:$pagingVersion")
    implementation("androidx.paging:paging-compose:$pagingVersion")
    testImplementation("androidx.paging:paging-testing:$pagingVersion")
}

PagingSource Implementation

class ArticlePagingSource(
    private val api: ArticleApi,
    private val query: String
) : PagingSource<Int, Article>() {

    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Article> {
        val page = params.key ?: 1
        return try {
            val response = api.searchArticles(
                query = query,
                page = page,
                pageSize = params.loadSize
            )
            LoadResult.Page(
                data = response.articles,
                prevKey = if (page == 1) null else page - 1,
                nextKey = if (response.articles.isEmpty()) null else page + 1
            )
        } catch (e: IOException) {
            LoadResult.Error(e)
        } catch (e: HttpException) {
            LoadResult.Error(e)
        }
    }

    override fun getRefreshKey(state: PagingState<Int, Article>): Int? {
        return state.anchorPosition?.let { anchor ->
            state.closestPageToPosition(anchor)?.prevKey?.plus(1)
                ?: state.closestPageToPosition(anchor)?.nextKey?.minus(1)
        }
    }
}

Cursor-Based PagingSource

class CursorArticlePagingSource(
    private val api: ArticleApi
) : PagingSource<String, Article>() {

    override suspend fun load(params: LoadParams<String>): LoadResult<String, Article> {
        return try {
            val response = api.getArticles(
                cursor = params.key,
                limit = params.loadSize
            )
            LoadResult.Page(
                data = response.articles,
                prevKey = null, // cursor-based usually does not support backward
                nextKey = response.nextCursor
            )
        } catch (e: Exception) {
            LoadResult.Error(e)
        }
    }

    override fun getRefreshKey(state: PagingState<String, Article>): String? = null
}