Multiplatform Paging

A Kotlin Multiplatform library for pagination.

Setup

This library is used on Kotlin Multiplatform that targets Android and iOS.

Check the table below for the compatibilty across versions

Library	Kotlin	Paging
0.3.1	1.4.10	3.0.0-alpha07
0.3.0	1.4.0	3.0.0-alpha06
0.2.0	1.3.70	3.0.0-alpha01
0.1.+	1.3.70	2.1.1
0.1.0	1.3.61	2.1.1

Add the jcenter repository on your Project-level gradle

allprojects {
    repositories {
        ...
        jcenter()
    }
}

On the module-level, add the library as an api dependency. The library needs to be propagated to the platforms.

On Android, it's automatically handled by Gradle. It will also add androidx.paging:paging-runtime:3.0.0-alpha06 as a transitive depenency

kotlin {
    ...
    sourceSets["commonMain"].dependencies {
        api("com.kuuuurt:multiplatform-paging:0.3.0")
    }
}

On iOS, you have to export it on your targets

If you're using the target shortcut for iOS:

kotlin {
    ...
    targets.named<KotlinNativeTarget>("iosX64") {
        binaries.withType<Framework>().configureEach {
            export("com.kuuuurt:multiplatform-paging-iosX64:0.3.0")
        }
    }

    targets.named<KotlinNativeTarget>("iosArm64") {
        binaries.withType<Framework>().configureEach {
            export("com.kuuuurt:multiplatform-paging-iosArm64:0.3.0")
        }
    }
}

If you're using a switching mechanism:

kotlin {
    ...
    val isDevice = System.getenv("SDK_NAME")?.startsWith("iphoneos") == true
    val pagingIos: String
    val iosTarget: (String, KotlinNativeTarget.() -> Unit) -> KotlinNativeTarget
    if (isDevice) {
        iosTarget = ::iosArm64
        pagingIos = "com.kuuuurt:multiplatform-paging-iosArm64:0.3.0"
    } else {
        iosTarget = ::iosX64
        pagingIos = "com.kuuuurt:multiplatform-paging-iosX64:0.3.0"
    }

    iosTarget("ios") {
        ...
        binaries.withType<Framework>().configureEach {
            export(pagingIos)
        }
    }
}

Usage

Common

Multiplatform paging exposes paginators which you can use in your multiplatform code to have common pagination on Android and iOS.

class MyMultiplatformController {
    val pager = Pager<Int, String>(
        clientScope = coroutineScope,
        config = PagingConfig(
            pageSize = 10,
            enablePlaceholders = false // Ignored on iOS
        ),
        initialKey = 1, // Key to use when initialized
        prevKey = { _, _ -> null }, // Key for previous page, null means don't load previous pages
        nextKey = { items, currentKey -> currentKey + 1 } // Key for next page. Use `items` or `currentKey` to get it depending on the pagination strategy 
        getItems = { startAt, size -> ... } // How you will get the items (API Call or Local DB)
    )

    val pagingData: CommonFlow<PagingData<String>>
        get() = pager.pagingData
            .cachedIn(clientScope) // cachedIn from AndroidX Paging. on iOS, this is a no-op
            .asCommonFlow() // So that iOS can consume the Flow 
}

Android

On Android, multiplatform paging uses Android Architecture Component's Paging library and exposes pagedList as a Flow<androidx.paging.PagedList<T>> which can be observed and submitted onto the PagedListAdapter.

class MyFragment : Fragment() {
    val myMultiplatformController = MyMultiplatformController()
    val myPagingDataAdapter = MyPagingDataAdapter()
    
    override fun onViewCreated(...) {
        super.onViewCreated(...)
      
        myMultiplatformController.pager.pagingData
            .onEach { myPagingDataAdapter.submitData(it) }
            .launchIn(viewLifecyleOwner.lifecyclerScope)     
    }
}

iOS

On iOS, it exposes pagedList as a Flow<List<T>> which can be observed and rendered to a UITableView

class MyViewController UIViewController, UITableViewDelegate, UITableViewDataSource {
    @IBOutlet weak var tableView: UITableView!
    
    let myMultiplatformController = MyMultiplatformController()
    
    private var data: [T] = []
    private var count: Int = 0
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // setup...
        
        myMultiplatformController.paginator.pagedList.watch { [unowned self] nullableArray in
            guard let list = nullableArray?.compactMap({ $0 as? T }) else {
                return
            }
      
            self.data = list
            self.count = list.count
            self.tableView.reloadData()
        }
    }
}

Disclaimer: I'm not an iOS developer and this is what I was able to make of. If someone has a better example, contributions are welcome!

Maintainers

• Kurt Renzo Acosta - kurt.r.acosta@gmail.com

Contributing

Feel free to dive in! Open an issue or submit PRs.

License

Apache-2.0 © Kurt Renzo Acosta