RxJava Homework #1

app/build.gradle

@@ -37,6 +37,7 @@ dependencies {
     implementation 'androidx.core:core-ktx:1.12.0'
     implementation 'com.squareup.retrofit2:retrofit:2.9.0'
     implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
+    implementation 'com.squareup.retrofit2:adapter-rxjava2:2.9.0'
     implementation 'com.google.code.gson:gson:2.10'
     implementation 'androidx.appcompat:appcompat:1.6.1'
     implementation 'com.google.android.material:material:1.11.0'

app/src/main/java/otus/homework/reactivecats/CatsService.kt

@@ -1,10 +1,10 @@
 package otus.homework.reactivecats
 
-import retrofit2.Call
+import io.reactivex.Single
 import retrofit2.http.GET
 
 interface CatsService {
 
     @GET("random?animal_type=cat")
-    fun getCatFact(): Call<Fact>
+    fun getCatFact(): Single<Fact>
 }

app/src/main/java/otus/homework/reactivecats/CatsViewModel.kt

@@ -5,40 +5,43 @@ import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
-import retrofit2.Call
-import retrofit2.Callback
-import retrofit2.Response
+import io.reactivex.Flowable
+import io.reactivex.android.schedulers.AndroidSchedulers
+import io.reactivex.disposables.CompositeDisposable
+import io.reactivex.schedulers.Schedulers
+import java.util.concurrent.TimeUnit
 
 class CatsViewModel(
-    catsService: CatsService,
-    localCatFactsGenerator: LocalCatFactsGenerator,
-    context: Context
+    private val catsService: CatsService,
+    private val localCatFactsGenerator: LocalCatFactsGenerator
 ) : ViewModel() {
 
     private val _catsLiveData = MutableLiveData<Result>()
     val catsLiveData: LiveData<Result> = _catsLiveData
 
+    private val compositeDisposable = CompositeDisposable()
+
     init {
-        catsService.getCatFact().enqueue(object : Callback<Fact> {
-            override fun onResponse(call: Call<Fact>, response: Response<Fact>) {
-                if (response.isSuccessful && response.body() != null) {
-                    _catsLiveData.value = Success(response.body()!!)
-                } else {
-                    _catsLiveData.value = Error(
-                        response.errorBody()?.string() ?: context.getString(
-                            R.string.default_error_text
-                        )
-                    )
-                }
-            }
+        getFacts()
+    }
 
-            override fun onFailure(call: Call<Fact>, t: Throwable) {
-                _catsLiveData.value = ServerError
-            }
-        })
+    private fun getFacts() {
+        compositeDisposable.add(
+            Flowable.interval(2, TimeUnit.SECONDS, Schedulers.io())
+                .subscribeOn(Schedulers.io())
+                .flatMapSingle {
+                    catsService.getCatFact()
+                        .onErrorResumeNext { localCatFactsGenerator.generateCatFact() }
+                }
+                .observeOn(AndroidSchedulers.mainThread())
+                .subscribe())
     }
 
-    fun getFacts() {}
+
+    override fun onCleared() {
+        super.onCleared()
+        compositeDisposable.clear()
+    }
 }
 
 class CatsViewModelFactory(
@@ -49,10 +52,11 @@ class CatsViewModelFactory(
     ViewModelProvider.NewInstanceFactory() {
 
     override fun <T : ViewModel> create(modelClass: Class<T>): T =
-        CatsViewModel(catsRepository, localCatFactsGenerator, context) as T
+        CatsViewModel(catsRepository, localCatFactsGenerator) as T
 }
 
 sealed class Result
 data class Success(val fact: Fact) : Result()
 data class Error(val message: String) : Result()
+object Loading : Result()
 object ServerError : Result()

app/src/main/java/otus/homework/reactivecats/DiContainer.kt

@@ -2,6 +2,7 @@ package otus.homework.reactivecats
 
 import android.content.Context
 import retrofit2.Retrofit
+import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
 import retrofit2.converter.gson.GsonConverterFactory
 
 class DiContainer {
@@ -10,6 +11,7 @@ class DiContainer {
         Retrofit.Builder()
             .baseUrl("https://cat-fact.herokuapp.com/facts/")
             .addConverterFactory(GsonConverterFactory.create())
+            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
             .build()
     }
 

app/src/main/java/otus/homework/reactivecats/LocalCatFactsGenerator.kt

@@ -3,7 +3,8 @@ package otus.homework.reactivecats
 import android.content.Context
 import io.reactivex.Flowable
 import io.reactivex.Single
-import kotlin.random.Random
+import io.reactivex.schedulers.Schedulers
+import java.util.concurrent.TimeUnit
 
 class LocalCatFactsGenerator(
     private val context: Context
@@ -14,8 +15,12 @@ class LocalCatFactsGenerator(
      * чтобы она возвращала Fact со случайной строкой  из массива строк R.array.local_cat_facts
      * обернутую в подходящий стрим(Flowable/Single/Observable и т.п)
      */
-    fun generateCatFact(): Single<Fact> {
-        return Single.never()
+    private val facts by lazy {
+        context.resources.getStringArray(R.array.local_cat_facts)
+    }
+
+    fun generateCatFact(): Single<Fact> = Single.fromCallable {
+        Fact(text = facts.random())
     }
 
     /**
@@ -24,7 +29,9 @@ class LocalCatFactsGenerator(
      * Если вновь заэмиченный Fact совпадает с предыдущим - пропускаем элемент.
      */
     fun generateCatFactPeriodically(): Flowable<Fact> {
-        val success = Fact(context.resources.getStringArray(R.array.local_cat_facts)[Random.nextInt(5)])
-        return Flowable.empty()
+        return Flowable
+            .interval(2, TimeUnit.SECONDS, Schedulers.io())
+            .map { Fact(text = facts.random()) }
+            .onBackpressureLatest()
     }
 }

app/src/main/java/otus/homework/reactivecats/MainActivity.kt

@@ -24,6 +24,7 @@ class MainActivity : AppCompatActivity() {
         setContentView(view)
         catsViewModel.catsLiveData.observe(this) { result ->
             when (result) {
+                is Loading ->  Snackbar.make(view, "Loading ...", 1000).show()
                 is Success -> view.populate(result.fact)
                 is Error -> Toast.makeText(this, result.message, Toast.LENGTH_LONG).show()
                 ServerError -> Snackbar.make(view, "Network error", 1000).show()