Multiplatform Paging

A library that adds additional Kotlin/Multiplatform targets to AndroidX Paging, and provides UI components to use Paging on iOS.

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 has a limited number of targets for paging-common and makes paging-runtime Android-specific, Multiplatform Paging adds many more targets to paging-common and provides paging-runtime-uikit, a UIKit-specific runtime for iOS. Therefore, pagination logic between many more targets can be shared, and the provided UI components can be used to render the paged items on Android and iOS.

Usage

For a holistic view of Multiplatform Paging, check out the GitHub Repository Search sample project, where there's an Android, Desktop, 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.

Like AndroidX Paging, all targets except for the JVM include the Paging 3 APIs only from AndroidX Paging. There are no plans to add support for Paging 2 APIs beyond the JVM.

JVM, iOS, Linux X64, and macOS

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

JS, MinGW, Linux Arm64, tvOS, and watchOS

app.cash.paging:paging-common on these targets delegate to our fork of AndroidX Paging.

paging-compose-common

The API of paging-compose-common in Multiplatform Paging is identical to that of paging-compose in AndroidX Paging (with the exception that the namespace has changed from androidx.paging to app.cash.paging).

To see how to use paging-compose-common, consult the official documentation of AndroidX Paging.

Android

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

JVM, iOS, JS, JVM, Linux X64, macOS, MinGW, tvOS, and watchOS

app.cash.paging:paging-compose-common on the these targets delegate to our fork of AndroidX Paging.

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
  }
}

paging-testing

The API of paging-testing in Multiplatform Paging is identical to that of paging-testing in AndroidX Paging (with the exception that the namespace has changed from androidx.paging to app.cash.paging). Therefore, to see how to use paging-testing, consult the official documentation of AndroidX Paging.

JVM, iOS, Linux X64, and macOS

app.cash.paging:paging-testing on these targets delegate to androidx.paging:paging-testing via type aliases. To understand what this means in practice, see the section Interoperability with AndroidX Paging.

JS, MinGW, Linux Arm64, tvOS, and watchOS

app.cash.paging:paging-common on these targets delegate to our fork of AndroidX Paging.

Interoperability with AndroidX Paging

As app.cash.paging:paging-common on the JVM, iOS, Linux X64, and macOS type alias to androidx.paging:paging-common, some useful side effects occur:

• The implementation of app.cash.paging:paging-common on the JVM, iOS, Linux X64, and macOS 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, iOS, Linux X64, or macOS.
• All libraries that depend on androidx.paging:paging-common can continue to be used. Some JVM-specific examples include androidx.paging:paging-runtime, androidx.paging:paging-compose, and 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 existing codebase to begin using Multiplatform Paging. The use of Multiplatform Paging is only necessary if you wish to share pagination logic on targets that AndroidX Paging don't yet support, or you want to use pagination UI bindings on platforms like iOS via paging-runtime-uikit.

A similar argument can be made for app.cash.paging:paging-compose-common and app.cash.paging:paging-testing.

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 3.3.0-alpha02 and Multiplatform Paging is on 0.5.1, the artifact for a release of paging-common will be app.cash.paging:paging-common:3.3.0-alpha02-0.5.1.

paging-common for common

implementation("app.cash.paging:paging-common:3.3.0-alpha02-0.5.1")

paging-compose-common for common

implementation("app.cash.paging:paging-compose-common:3.3.0-alpha02-0.5.1")

paging-runtime-uikit for iOS

implementation("app.cash.paging:paging-runtime-uikit:3.3.0-alpha02-0.5.1")

paging-testing for common

implementation("app.cash.paging:paging-testing:3.3.0-alpha02-0.5.1")

Android

Use the official AndroidX Paging dependencies.

implementation("androidx.paging:paging-runtime:3.3.0-alpha02")
implementation("androidx.paging:paging-compose:3.3.0-alpha02")
implementation("androidx.paging:paging-rxjava3:3.3.0-alpha02")
// 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.