Implement UseCase#2 with RxJava

Author: LukasLechnerDev

README.md

@@ -45,14 +45,17 @@ Unit Tests exist for most use cases.
 
 ### 1. Perform single network request
 
-Performs a single network request to get the latest Android Versions.
+This use case performs a single network request to get the latest Android Versions and displays them on the screen.
 
 [[code](app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase1/PerformSingleNetworkRequestViewModel.kt)]
 
 ### 2. Perform two sequential network requests
 
-Performs two network requests sequentially. First it retrieves recent Android Versions and then it requests the features of the latest version.
-There also exists an alternative implementation for this use case which uses traditional callbacks. It should demonstrate the simplicity of the Coroutine version compared to callback-based version.
+This use case performs two network requests sequentially. First it retrieves recent Android Versions and then it requests the features of the latest version.
+
+There are also 2 alternative implementations included. One is using old-school [callbacks](app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/SequentialNetworkRequestsCallbacksViewModel.kt).
+The other one uses [RxJava](app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/rx/SequentialNetworkRequestsRxViewModel.kt). You can compare each implementation.
+If you compare all implementation, it is really interesting to see, in my opinion, how simple the Coroutine-based version actually is.
 
 [[code](app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/Perform2SequentialNetworkRequestsViewModel.kt)]
 

app/build.gradle

@@ -59,9 +59,14 @@ dependencies {
     implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
 
     implementation 'com.squareup.retrofit2:retrofit:2.7.1'
+    implementation 'com.squareup.retrofit2:adapter-rxjava2:2.7.1'
     implementation 'com.google.code.gson:gson:2.8.6'
     implementation 'com.squareup.retrofit2:converter-gson:2.7.1'
 
+    implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
+    implementation 'io.reactivex.rxjava2:rxjava:2.2.19'
+    implementation 'io.reactivex.rxjava2:rxkotlin:2.4.0'
+
     implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
 
     def work_manager_version = "2.3.4"

app/src/main/AndroidManifest.xml

@@ -21,7 +21,8 @@
         <activity android:name=".base.UseCaseActivity" />
         <activity android:name=".usecases.coroutines.usecase1.PerformSingleNetworkRequestActivity" />
         <activity android:name=".usecases.coroutines.usecase2.Perform2SequentialNetworkRequestsActivity" />
-        <activity android:name=".usecases.coroutines.usecase2.usingcallbacks.SequentialNetworkRequestsCallbacksActivity" />
+        <activity android:name=".usecases.coroutines.usecase2.callbacks.SequentialNetworkRequestsCallbacksActivity" />
+        <activity android:name=".usecases.coroutines.usecase2.rx.SequentialNetworkRequestsRxActivity" />
         <activity android:name=".usecases.coroutines.usecase3.PerformNetworkRequestsConcurrentlyActivity" />
         <activity android:name=".usecases.coroutines.usecase4.VariableAmountOfNetworkRequestsActivity" />
         <activity android:name=".usecases.coroutines.usecase5.NetworkRequestWithTimeoutActivity" />

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/base/UseCase.kt

@@ -12,7 +12,8 @@ import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase14
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase15.WorkManagerActivity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase16.PerformanceAnalysisActivity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.Perform2SequentialNetworkRequestsActivity
-import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks.SequentialNetworkRequestsCallbacksActivity
+import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks.SequentialNetworkRequestsCallbacksActivity
+import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.rx.SequentialNetworkRequestsRxActivity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase3.PerformNetworkRequestsConcurrentlyActivity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase4.VariableAmountOfNetworkRequestsActivity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase5.NetworkRequestWithTimeoutActivity
@@ -35,6 +36,7 @@ data class UseCaseCategory(val categoryName: String, val useCases: List<UseCase>
 const val useCase1Description = "#1 Perform single network request"
 const val useCase2Description = "#2 Perform two sequential network requests"
 const val useCase2UsingCallbacksDescription = "#2 using Callbacks"
+const val useCase2UsingRxDescription = "#2 using RxJava"
 const val useCase3Description = "#3 Perform several network requests concurrently"
 const val useCase4Description = "#4 Perform variable amount of network requests"
 const val useCase5Description = "#5 Network request with TimeOut"
@@ -65,6 +67,9 @@ private val coroutinesUseCases =
             UseCase(
                 useCase2UsingCallbacksDescription,
                 SequentialNetworkRequestsCallbacksActivity::class.java
+            ), UseCase(
+                useCase2UsingRxDescription,
+                SequentialNetworkRequestsRxActivity::class.java
             ),
             UseCase(
                 useCase3Description,

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/MockApi.kt app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/MockApi.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.google.gson.Gson
 import com.lukaslechner.coroutineusecasesonandroid.mock.AndroidVersion

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/SequentialNetworkRequestsCallbacksActivity.kt app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/SequentialNetworkRequestsCallbacksActivity.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import android.os.Bundle
 import androidx.activity.viewModels

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/SequentialNetworkRequestsCallbacksViewModel.kt app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/SequentialNetworkRequestsCallbacksViewModel.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.lukaslechner.coroutineusecasesonandroid.base.BaseViewModel
 import com.lukaslechner.coroutineusecasesonandroid.mock.AndroidVersion

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/UiState.kt app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/UiState.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.lukaslechner.coroutineusecasesonandroid.mock.VersionFeatures
 

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/rx/MockApi.kt

@@ -0,0 +1,56 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.rx
+
+import com.google.gson.Gson
+import com.lukaslechner.coroutineusecasesonandroid.mock.AndroidVersion
+import com.lukaslechner.coroutineusecasesonandroid.mock.VersionFeatures
+import com.lukaslechner.coroutineusecasesonandroid.mock.mockAndroidVersions
+import com.lukaslechner.coroutineusecasesonandroid.mock.mockVersionFeaturesAndroid10
+import com.lukaslechner.coroutineusecasesonandroid.utils.MockNetworkInterceptor
+import io.reactivex.Single
+import io.reactivex.schedulers.Schedulers
+import okhttp3.OkHttpClient
+import retrofit2.Retrofit
+import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
+import retrofit2.converter.gson.GsonConverterFactory
+import retrofit2.http.GET
+import retrofit2.http.Path
+
+fun mockApi(): RxMockApi = createMockApi(
+    MockNetworkInterceptor()
+        .mock(
+            "http://localhost/recent-android-versions",
+            Gson().toJson(mockAndroidVersions),
+            200,
+            1500
+        )
+        .mock(
+            "http://localhost/android-version-features/29",
+            Gson().toJson(mockVersionFeaturesAndroid10),
+            200,
+            1500
+        )
+)
+
+interface RxMockApi {
+
+    @GET("recent-android-versions")
+    fun getRecentAndroidVersions(): Single<List<AndroidVersion>>
+
+    @GET("android-version-features/{apiVersion}")
+    fun getAndroidVersionFeatures(@Path("apiVersion") apiVersion: Int): Single<VersionFeatures>
+}
+
+fun createMockApi(interceptor: MockNetworkInterceptor): RxMockApi {
+    val okHttpClient = OkHttpClient.Builder()
+        .addInterceptor(interceptor)
+        .build()
+
+    val retrofit = Retrofit.Builder()
+        .baseUrl("http://localhost/")
+        .client(okHttpClient)
+        .addConverterFactory(GsonConverterFactory.create())
+        .addCallAdapterFactory(RxJava2CallAdapterFactory.createWithScheduler(Schedulers.io()))
+        .build()
+
+    return retrofit.create(RxMockApi::class.java)
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/rx/SequentialNetworkRequestsRxActivity.kt

@@ -0,0 +1,74 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.rx
+
+import android.os.Bundle
+import androidx.activity.viewModels
+import androidx.lifecycle.Observer
+import com.lukaslechner.coroutineusecasesonandroid.base.BaseActivity
+import com.lukaslechner.coroutineusecasesonandroid.base.useCase2UsingRxDescription
+import com.lukaslechner.coroutineusecasesonandroid.databinding.ActivityPerform2sequentialnetworkrequestsBinding
+import com.lukaslechner.coroutineusecasesonandroid.utils.fromHtml
+import com.lukaslechner.coroutineusecasesonandroid.utils.setGone
+import com.lukaslechner.coroutineusecasesonandroid.utils.setVisible
+import com.lukaslechner.coroutineusecasesonandroid.utils.toast
+
+class SequentialNetworkRequestsRxActivity : BaseActivity() {
+
+    private val binding by lazy {
+        ActivityPerform2sequentialnetworkrequestsBinding.inflate(
+            layoutInflater
+        )
+    }
+
+    private val viewModel: SequentialNetworkRequestsRxViewModel by viewModels()
+
+    override fun getToolbarTitle() = useCase2UsingRxDescription
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(binding.root)
+        viewModel.uiState().observe(this, Observer { uiState ->
+            if (uiState != null) {
+                render(uiState)
+            }
+        })
+        binding.btnRequestsSequentially.setOnClickListener {
+            viewModel.perform2SequentialNetworkRequest()
+        }
+    }
+
+    private fun render(uiState: UiState) {
+        when (uiState) {
+            is UiState.Loading -> {
+                onLoad()
+            }
+            is UiState.Success -> {
+                onSuccess(uiState)
+            }
+            is UiState.Error -> {
+                onError(uiState)
+            }
+        }
+    }
+
+    private fun onLoad() = with(binding) {
+        progressBar.setVisible()
+        textViewResult.text = ""
+    }
+
+    private fun onSuccess(uiState: UiState.Success) = with(binding) {
+        progressBar.setGone()
+        textViewResult.text = fromHtml(
+            "<b>Features of most recent Android Version \" ${uiState.versionFeatures.androidVersion.name} \"</b><br>" +
+                    uiState.versionFeatures.features.joinToString(
+                        prefix = "- ",
+                        separator = "<br>- "
+                    )
+        )
+    }
+
+    private fun onError(uiState: UiState.Error) = with(binding) {
+        progressBar.setGone()
+        btnRequestsSequentially.isEnabled = true
+        toast(uiState.message)
+    }
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/rx/SequentialNetworkRequestsRxViewModel.kt

@@ -0,0 +1,41 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.rx
+
+import com.lukaslechner.coroutineusecasesonandroid.base.BaseViewModel
+import io.reactivex.android.schedulers.AndroidSchedulers
+import io.reactivex.disposables.CompositeDisposable
+import io.reactivex.rxkotlin.addTo
+import io.reactivex.rxkotlin.subscribeBy
+import io.reactivex.schedulers.Schedulers
+
+class SequentialNetworkRequestsRxViewModel(
+    private val mockApi: RxMockApi = mockApi()
+) : BaseViewModel<UiState>() {
+
+    private val disposables = CompositeDisposable()
+
+    fun perform2SequentialNetworkRequest() {
+        uiState.value = UiState.Loading
+
+        mockApi.getRecentAndroidVersions()
+            .flatMap { androidVersions ->
+                val recentVersion = androidVersions.last()
+                mockApi.getAndroidVersionFeatures(recentVersion.apiVersion)
+            }
+            .subscribeOn(Schedulers.io())
+            .observeOn(AndroidSchedulers.mainThread())
+            .subscribeBy(
+                onSuccess = { featureVersions ->
+                    uiState.value = UiState.Success(featureVersions)
+                },
+                onError = {
+                    uiState.value = UiState.Error("Network Request failed.")
+                }
+            )
+            .addTo(disposables)
+    }
+
+    override fun onCleared() {
+        super.onCleared()
+        disposables.clear()
+    }
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/rx/UiState.kt

@@ -0,0 +1,12 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.rx
+
+import com.lukaslechner.coroutineusecasesonandroid.mock.VersionFeatures
+
+sealed class UiState {
+    object Loading : UiState()
+    data class Success(
+        val versionFeatures: VersionFeatures
+    ) : UiState()
+
+    data class Error(val message: String) : UiState()
+}

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/FakeFeaturesErrorApi.kt app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/FakeFeaturesErrorApi.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.lukaslechner.coroutineusecasesonandroid.mock.AndroidVersion
 import com.lukaslechner.coroutineusecasesonandroid.mock.VersionFeatures

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/FakeSuccessApi.kt app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/FakeSuccessApi.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.lukaslechner.coroutineusecasesonandroid.mock.*
 import retrofit2.Call

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/FakeVersionsErrorApi.kt app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/FakeVersionsErrorApi.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import com.lukaslechner.coroutineusecasesonandroid.mock.AndroidVersion
 import com.lukaslechner.coroutineusecasesonandroid.mock.VersionFeatures

app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/usingcallbacks/SequentialNetworkRequestsCallbacksViewModelTest.kt app/src/test/java/com/lukaslechner/coroutineusecasesonandroid/usecases/coroutines/usecase2/callbacks/SequentialNetworkRequestsCallbacksViewModelTest.kt

@@ -1,4 +1,4 @@
-package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.usingcallbacks
+package com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase2.callbacks
 
 import androidx.arch.core.executor.testing.InstantTaskExecutorRule
 import com.lukaslechner.coroutineusecasesonandroid.mock.mockVersionFeaturesAndroid10