Introduce kotlin coroutines flow

androidApp/build.gradle.kts

@@ -27,7 +27,7 @@ android {
   }
 
   lintOptions {
-    setAbortOnError(false)
+    isAbortOnError = false
   }
   compileOptions {
     sourceCompatibility = JavaVersion.VERSION_1_8
@@ -46,15 +46,18 @@ dependencies {
   implementation(kotlin("stdlib-jdk7", KotlinCompilerVersion.VERSION))
   implementation(project(":shared"))
 
-  implementation("androidx.constraintlayout:constraintlayout:2.0.0-beta1")
-  implementation("androidx.appcompat:appcompat:1.0.2")
+  implementation("androidx.constraintlayout:constraintlayout:2.0.0-beta2")
+  implementation("androidx.appcompat:appcompat:1.1.0")
   implementation("androidx.recyclerview:recyclerview:1.0.0")
-  implementation("androidx.lifecycle:lifecycle-runtime:2.0.0")
-  implementation("androidx.lifecycle:lifecycle-extensions:2.0.0")
+  implementation("androidx.lifecycle:lifecycle-runtime:2.1.0")
+  implementation("androidx.lifecycle:lifecycle-extensions:2.1.0")
   implementation("com.github.pedrovgs:renderers:3.4.0")
-  implementation("com.squareup.okhttp3:okhttp:3.11.0")
+  implementation("com.squareup.okhttp3:okhttp:3.12.1")
   implementation("com.squareup.picasso:picasso:2.71828")
 
+  implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.1")
+  implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.1")
+
   testImplementation("junit:junit:4.12")
   androidTestImplementation("org.mockito:mockito-android:2.28.2")
   androidTestImplementation("com.nhaarman.mockitokotlin2:mockito-kotlin:2.1.0")

androidApp/src/main/kotlin/com/karumi/gallery/app/MainActivity.kt

@@ -33,20 +33,29 @@ class MainActivity : AppCompatActivity(), PhotoListPresenter.View {
     presenter.detachView()
   }
 
-  override fun showLoader() {
-    progress.visibility = View.VISIBLE
+  override fun render(state: PhotoListPresenter.View.State) {
+    when (state) {
+      is PhotoListPresenter.View.State.Loading -> renderLoading()
+      is PhotoListPresenter.View.State.Error -> renderError()
+      is PhotoListPresenter.View.State.Success -> renderPhotos(state.photos)
+    }
   }
 
-  override fun hideLoader() {
-    progress.visibility = View.GONE
+  private fun renderLoading() {
+    progress.visibility = View.VISIBLE
+    errorInformation.visibility = View.GONE
   }
 
-  override fun onLoadError() {
+  private fun renderError() {
+    progress.visibility = View.GONE
     errorInformation.visibility = View.VISIBLE
   }
 
-  override fun plusAssign(shots: List<PhotoShot>) {
-    val items = shots.map { PhotoItem(it.id, it.thumbnailUrl, it.authorName) }
+  private fun renderPhotos(photos: List<PhotoShot>) {
+    progress.visibility = View.GONE
+    errorInformation.visibility = View.GONE
+
+    val items = photos.map { PhotoItem(it.id, it.thumbnailUrl, it.authorName) }
     adapter.addAll(items)
     adapter.notifyDataSetChanged()
   }

iosApp/PhotoGallery/PhotoCollectionViewCell.xib

@@ -1,28 +1,28 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES">
     <device id="retina4_7" orientation="portrait">
         <adaptation id="fullscreen"/>
     </device>
     <dependencies>
         <deployment identifier="iOS"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14460.20"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14490.49"/>
         <capability name="Safe area layout guides" minToolsVersion="9.0"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <objects>
         <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
         <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
-        <collectionViewCell opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" reuseIdentifier="PhotoCollectionViewCellReuseIdentifier" id="Kvj-ya-9xL" customClass="PhotoCollectionViewCell" customModule="Dribbble_app" customModuleProvider="target">
+        <collectionViewCell opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" reuseIdentifier="PhotoCollectionViewCellReuseIdentifier" id="Kvj-ya-9xL" customClass="PhotoCollectionViewCell" customModule="PhotoGallery" customModuleProvider="target">
             <rect key="frame" x="0.0" y="0.0" width="220" height="204"/>
             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
             <view key="contentView" opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" insetsLayoutMarginsFromSafeArea="NO">
                 <rect key="frame" x="0.0" y="0.0" width="220" height="204"/>
                 <autoresizingMask key="autoresizingMask"/>
                 <subviews>
-                    <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="eiD-pr-Gu4">
+                    <imageView clipsSubviews="YES" userInteractionEnabled="NO" contentMode="scaleAspectFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="eiD-pr-Gu4">
                         <rect key="frame" x="0.0" y="0.0" width="220" height="188"/>
                     </imageView>
-                    <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="RoS-jn-q9a">
+                    <imageView clipsSubviews="YES" userInteractionEnabled="NO" contentMode="scaleAspectFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" translatesAutoresizingMaskIntoConstraints="NO" id="RoS-jn-q9a">
                         <rect key="frame" x="0.0" y="0.0" width="220" height="188"/>
                     </imageView>
                     <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="by Nick Slater" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="gqP-3L-qtE">

iosApp/PhotoGallery/PhotoListViewController.swift

@@ -23,24 +23,34 @@ class PhotoListViewController: UIViewController, PhotoListPresenterView {
         errorTextLabel.isHidden = true
     }
 
-    func plusAssign(shots: [PhotoShot]) {
-        let newItems = shots.map(PhotoListItem.init)
-        items.append(contentsOf: newItems)
-        allItemsCollectionView.reloadData()
+    func render(state: PhotoListPresenterViewState) {
+        if state is PhotoListPresenterViewState.Loading {
+            renderLoading()
+        } else if state is PhotoListPresenterViewState.Error {
+            renderError()
+        } else if let state = state as? PhotoListPresenterViewState.Success {
+            render(photos: state.photos)
+        }
     }
-    
-    func showLoader() {
+
+    func renderLoading() {
         loadingIndicator.startAnimating()
+        errorTextLabel.isHidden = true
     }
 
-    func hideLoader() {
-        loadingIndicator.stopAnimating()
+    func renderError() {
         loadingIndicator.isHidden = true
-    }
-
-    func onLoadError() {
         errorTextLabel.isHidden = false
     }
+
+    func render(photos: [PhotoShot]) {
+        loadingIndicator.isHidden = true
+        errorTextLabel.isHidden = true
+
+        let newItems = photos.map(PhotoListItem.init)
+        items.append(contentsOf: newItems)
+        allItemsCollectionView.reloadData()
+    }
 }
 
 extension PhotoListViewController: UICollectionViewDelegateFlowLayout {

shared/build.gradle

@@ -4,8 +4,8 @@ group 'com.karumi'
 version '0.0.1'
 
 apply plugin: "kotlin-multiplatform"
-apply plugin: 'com.android.library'
 apply plugin: "kotlinx-serialization"
+apply plugin: 'com.android.library'
 apply plugin: "io.gitlab.arturbosch.detekt"
 apply plugin: "org.jlleitschuh.gradle.ktlint"
 
@@ -31,52 +31,56 @@ kotlin {
         all {
             languageSettings {
                 useExperimentalAnnotation('kotlin.Experimental')
+                useExperimentalAnnotation('kotlin.time.ExperimentalTime')
+                useExperimentalAnnotation('kotlinx.coroutines.FlowPreview')
+                useExperimentalAnnotation('kotlinx.coroutines.ExperimentalCoroutinesApi')
             }
         }
         commonMain {
             dependencies {
-                implementation "org.jetbrains.kotlin:kotlin-stdlib-common:$kotlin_version"
+                implementation 'org.jetbrains.kotlin:kotlin-stdlib'
+
                 implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core-common:$coroutines_version"
                 implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime-common:$serialization_version"
 
                 implementation "io.ktor:ktor-client-core:$ktor_version"
                 implementation "io.ktor:ktor-client-json:$ktor_version"
+                implementation "io.ktor:ktor-client-logging:$ktor_version"
                 implementation "io.ktor:ktor-client-serialization:$ktor_version"
             }
         }
         commonTest {
             dependencies {
                 implementation "org.jetbrains.kotlin:kotlin-test-common:$kotlin_version"
                 implementation "org.jetbrains.kotlin:kotlin-test-annotations-common:$kotlin_version"
-                implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core-common:$coroutines_version"
 
-                //implementation "io.ktor:ktor-client-mock-native:$ktor_version"
+                implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version"
+
                 api "io.ktor:ktor-client-mock:$ktor_version"
             }
         }
         androidMain {
             dependencies {
                 implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
-                implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version"
+
                 implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
                 implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:$serialization_version"
 
                 implementation "io.ktor:ktor-client-android:$ktor_version"
                 implementation "io.ktor:ktor-client-core-jvm:$ktor_version"
                 implementation "io.ktor:ktor-client-json-jvm:$ktor_version"
+                implementation "io.ktor:ktor-client-logging-jvm:$ktor_version"
                 implementation "io.ktor:ktor-client-serialization-jvm:$ktor_version"
             }
         }
         androidTest {
             dependencies {
                 implementation "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
 
-                implementation "io.ktor:ktor-client-mock-jvm:$ktor_version"
+                implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version"
+                implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$coroutines_version"
 
-                // TODO below dependencies can be removed after KT-29343 is fixed
-                implementation "io.ktor:ktor-client-core-jvm:$ktor_version"
-                implementation "io.ktor:ktor-client-json-jvm:$ktor_version"
-                implementation "io.ktor:ktor-client-serialization-jvm:$ktor_version"
+                implementation "io.ktor:ktor-client-mock-jvm:$ktor_version"
             }
         }
         iosMain {
@@ -87,6 +91,7 @@ kotlin {
                 implementation "io.ktor:ktor-client-ios:$ktor_version"
                 implementation "io.ktor:ktor-client-core-native:$ktor_version"
                 implementation "io.ktor:ktor-client-json-native:$ktor_version"
+                implementation "io.ktor:ktor-client-logging-native:$ktor_version"
                 implementation "io.ktor:ktor-client-serialization-native:$ktor_version"
             }
         }

shared/src/androidMain/kotlin/com/karumi/gallery/AndroidLogger.kt

@@ -2,8 +2,8 @@ package com.karumi.gallery
 
 import android.util.Log
 
-actual fun logError(tag: String, message: String) {
-  Log.e(tag, message)
+actual fun logError(tag: String, message: String, error: Throwable?) {
+  Log.e(tag, message, error)
 }
 
 actual fun logInfo(tag: String, message: String) {

shared/src/androidMain/kotlin/com/karumi/gallery/app/androidAsync.kt

@@ -2,12 +2,15 @@ package com.karumi.gallery.app
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.launch
 import kotlin.coroutines.CoroutineContext
 
-actual fun launchInMain(block: suspend CoroutineScope.() -> Unit) =
-  GlobalScope.launch(Dispatchers.Main) { block() }
+actual fun CoroutineScope.launchInMain(block: suspend CoroutineScope.() -> Unit) =
+  launch(Dispatchers.Main) { block() }
+
+actual fun <T> Flow<T>.flowOnBackground(): Flow<T> = flowOn(Dispatchers.Default)
 
 actual fun <T> runBlocking(context: CoroutineContext, block: suspend CoroutineScope.() -> T): T =
   kotlinx.coroutines.runBlocking(context, block)

shared/src/commonMain/kotlin/com/karumi/gallery/Logger.kt

@@ -1,4 +1,4 @@
 package com.karumi.gallery
 
-expect fun logError(tag: String, message: String)
+expect fun logError(tag: String, message: String, error: Throwable? = null)
 expect fun logInfo(tag: String, message: String)

shared/src/commonMain/kotlin/com/karumi/gallery/app/GalleryInjector.kt

@@ -2,6 +2,7 @@ package com.karumi.gallery.app
 
 import com.karumi.gallery.data.PhotosApiClient
 import com.karumi.gallery.data.getEngine
+import com.karumi.gallery.domain.PhotosFlow
 import com.karumi.gallery.generated.KotlinConfig
 import com.karumi.gallery.usecase.GetPhotos
 import kotlin.native.concurrent.ThreadLocal
@@ -24,5 +25,8 @@ open class InjectionModule {
     PhotosApiClient(getEngine(), KotlinConfig.UNPLASH_KEY)
 
   open fun getPhotos(): GetPhotos =
-    GetPhotos(getPhotosApiClient())
+    GetPhotos(getPhotosFlow())
+
+  open fun getPhotosFlow(): PhotosFlow =
+    PhotosFlow(getPhotosApiClient())
 }

shared/src/commonMain/kotlin/com/karumi/gallery/app/PhotoListPresenter.kt

@@ -1,48 +1,42 @@
 package com.karumi.gallery.app
 
-import com.karumi.gallery.logError
-import com.karumi.gallery.logInfo
-import com.karumi.gallery.model.PhotoShot
+import com.karumi.gallery.model.Photos
 import com.karumi.gallery.usecase.GetPhotos
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.collect
+import kotlin.coroutines.CoroutineContext
 
 class PhotoListPresenter(
   private val view: View,
   private val getAllPhotos: GetPhotos
-) {
+) : CoroutineScope {
 
-  companion object {
-    private const val TAG = "PhotoListPresenter"
-  }
+  override val coroutineContext: CoroutineContext
+    get() = job
 
-  private var getPhotosJob: Job? = null
-
-  fun onCreate() {
-    view.showLoader()
-    getPhotosJob = launchInMain {
-      try {
-        logInfo(TAG, "Start getting photos")
-
-        val allShots = getAllPhotos()
-        view += allShots
-        logInfo(TAG, "${allShots.size} photos received")
-      } catch (ex: Exception) {
-        logError(TAG, "Load photos error: ${ex.message}")
-        view.onLoadError()
-      } finally {
-        view.hideLoader()
-      }
-    }
+  private val job = Job()
+
+  fun onCreate() = launchInMain {
+    view.render(View.State.Loading)
+    getAllPhotos()
+      .flowOnBackground()
+      .catch { view.render(View.State.Error) }
+      .collect { view.render(View.State.Success(it)) }
   }
 
   fun detachView() {
-    getPhotosJob?.cancel()
+    job.cancel()
   }
 
   interface View {
-    operator fun plusAssign(shots: List<PhotoShot>)
-    fun showLoader()
-    fun hideLoader()
-    fun onLoadError()
+    fun render(state: State)
+
+    sealed class State {
+      object Loading : State()
+      object Error : State()
+      data class Success(val photos: Photos) : State()
+    }
   }
 }

shared/src/commonMain/kotlin/com/karumi/gallery/app/async.kt

@@ -2,10 +2,13 @@ package com.karumi.gallery.app
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.Flow
 import kotlin.coroutines.CoroutineContext
 import kotlin.coroutines.EmptyCoroutineContext
 
-expect fun launchInMain(block: suspend CoroutineScope.() -> Unit): Job
+expect fun CoroutineScope.launchInMain(block: suspend CoroutineScope.() -> Unit): Job
+
+expect fun <T> Flow<T>.flowOnBackground(): Flow<T>
 
 expect fun <T> runBlocking(
   context: CoroutineContext = EmptyCoroutineContext,