Multiplatform Paging

A library that packages AndroidX Paging for Kotlin/Multiplatform.

Introduction

As with AndroidX Paging, the primary modules of Multiplatform Paging are:

• paging-common – encompasses the repository layer and the view model layer
• paging-runtime – encompasses the UI layer

Unlike AndroidX Paging that makes paging-common JVM-specific and paging-runtime Android-specific, Multiplatform Paging makes paging-common multiplatform and provides paging-runtime-uikit, a UIKit-specific runtime for iOS. Therefore, pagination logic between Android and iOS can be shared, and the provided UI components can be used to render the paged items on Android and iOS.

Usage

❗Looking for a multiplatform version of paging-compose? Or support for version 3.2.0-alpha05 of AndroidX Paging instead of 3.1.1? Then check out this README instead!

For a holistic view of Multiplatform Paging, check out the GitHub Repository Search sample project, where there's an Android and iOS app, along with shared pagination logic.

paging-common

The API of paging-common in Multiplatform Paging is identical to that of paging-common in AndroidX Paging (with the exception that: the namespace has changed from androidx.paging to app.cash.paging; there are some minor API discrepancies due to limitations in the Kotlin compiler). Therefore, to see how to use paging-common, consult the official documentation of AndroidX Paging.

JVM

app.cash.paging:paging-common on the JVM delegates to androidx.paging:paging-common via type aliases. To understand what this means in practice, see the section Interoperability with AndroidX Paging.

iOS

app.cash.paging:paging-common on iOS delegates to our fork of AndroidX Paging.

iOS only includes the Paging 3 APIs from AndroidX Paging. We don't plan on offering Paging 2 support for iOS, though you can continue to use Paging 2 on the JVM.

paging-runtime for Android

See the Interoperability with AndroidX Paging section below.

paging-runtime-uikit for iOS

The PagingCollectionViewController allows a PagingData to be rendered via a UICollectionView. The PagingCollectionViewController mimics the UICollectionViewController, providing: the cell count; and item retrieval via IndexPath.

Here's an example in Swift:

final class FooViewController: UICollectionViewController {

  private let delegate = Paging_runtime_uikitPagingCollectionViewController<Foo>()

  private let presenter = …

  required init(coder: NSCoder) {
    super.init(coder: coder)!
    presenter.pagingDatas
      .sink { pagingData in
        self.delegate.submitData(pagingData: pagingData, completionHandler: …)
      }
  }

  override func collectionView(
    _ collectionView: UICollectionView,
    numberOfItemsInSection section: Int
  ) -> Int {
    return Int(delegate.collectionView(collectionView: collectionView, numberOfItemsInSection: Int64(section)))
  }

  override func collectionView(
    _ collectionView: UICollectionView,
    cellForItemAt indexPath: IndexPath
  ) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "FooCell", for: indexPath) as! FooCell

    let item = delegate.getItem(position: Int32(indexPath.row))!
    // …

    return cell
  }
}

Interoperability with AndroidX Paging

As app.cash.paging:paging-common on the JVM type aliases to androidx.paging:paging-common, some useful side effects occur:

• The implementation of app.cash.paging:paging-common on the JVM is identical to androidx.paging:paging-common. This means that it is impossible for there to be a behavioral discrepancy when using app.cash.paging:paging-common on the JVM.
• All libraries that depend on androidx.paging:paging-common can continue to be used on the JVM (e.g., androidx.paging:paging-runtime, androidx.paging:paging-compose, androidx.paging:paging-rxjava3). This is why there aren't additional paging-runtime artifacts to support Android's UI toolkit, as you can instead depend on the official AndroidX artifact.
• If you're already using AndroidX Paging, you don't need to refactor your Android code to use Multiplatform Paging. The use of Multiplatform Paging is only necessary if you wish to share pagination logic in common code and/or paginate on iOS.

Releases

The versioning scheme is of the form X-Y where:

• X is the AndroidX Paging version that is being tracked.
• Y is the Multiplatform Paging version.

For example, if AndroidX Paging is on 3.1.1 and Multiplatform Paging is on 0.3.1, the artifact for a release of paging-common will be app.cash.paging:paging-common:3.1.1-0.3.1.

paging-common for common

implementation("app.cash.paging:paging-common:3.1.1-0.3.1")

paging-runtime-uikit for iOS

implementation("app.cash.paging:paging-runtime-uikit:3.1.1-0.3.1")

Android

Use the official AndroidX Paging dependencies.

implementation("androidx.paging:paging-runtime:3.1.1")
implementation("androidx.paging:paging-compose:1.0.0-alpha17")
implementation("androidx.paging:paging-rxjava3:3.1.1")
// etc.

License

Copyright 2022 Block, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.