Kulish D. Flow Homework

flowcats/build.gradle

@@ -4,13 +4,13 @@ plugins {
 }
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
     buildToolsVersion "30.0.3"
 
     defaultConfig {
         applicationId "otus.homework.flowcats"
         minSdkVersion 23
-        targetSdkVersion 30
+        targetSdkVersion 31
         versionCode 1
         versionName "1.0"
 
@@ -46,4 +46,5 @@ dependencies {
     implementation 'androidx.activity:activity-ktx:1.2.3'
     testImplementation 'org.jetbrains.kotlinx:kotlinx-coroutines-test:1.4.3'
     implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.1'
+    implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.4.1")
 }

flowcats/src/main/java/otus/homework/flowcats/CatsRepository.kt

@@ -1,7 +1,9 @@
 package otus.homework.flowcats
 
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOn
 
 class CatsRepository(
     private val catsService: CatsService,
@@ -14,5 +16,5 @@ class CatsRepository(
             emit(latestNews)
             delay(refreshIntervalMs)
         }
-    }
+    }.flowOn(Dispatchers.IO)
 }

flowcats/src/main/java/otus/homework/flowcats/CatsView.kt

@@ -14,9 +14,14 @@ class CatsView @JvmOverloads constructor(
     override fun populate(fact: Fact) {
         findViewById<TextView>(R.id.fact_textView).text = fact.text
     }
+
+    override fun showError(error: String) {
+        findViewById<TextView>(R.id.fact_textView).text = error
+    }
 }
 
 interface ICatsView {
 
     fun populate(fact: Fact)
+    fun showError(error : String)
 }

flowcats/src/main/java/otus/homework/flowcats/CatsViewModel.kt

@@ -1,7 +1,12 @@
 package otus.homework.flowcats
 
-import androidx.lifecycle.*
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -10,15 +15,19 @@ class CatsViewModel(
     private val catsRepository: CatsRepository
 ) : ViewModel() {
 
-    private val _catsLiveData = MutableLiveData<Fact>()
-    val catsLiveData: LiveData<Fact> = _catsLiveData
+    private val _catsStateFlow = MutableStateFlow<Result<Fact>>(Result.Empty("Fetching..."))
+    val catsStateFlow: StateFlow<Result<Fact>> = _catsStateFlow
 
     init {
         viewModelScope.launch {
-            withContext(Dispatchers.IO) {
-                catsRepository.listenForCatFacts().collect {
-                    _catsLiveData.value = it
-                }
+            withContext(Dispatchers.Main) {
+                catsRepository.listenForCatFacts()
+                    .catch {
+                        _catsStateFlow.emit(Result.Error(it))
+                    }
+                    .collect {
+                        _catsStateFlow.emit(Result.Success(it))
+                    }
             }
         }
     }

flowcats/src/main/java/otus/homework/flowcats/MainActivity.kt

@@ -1,8 +1,13 @@
 package otus.homework.flowcats
 
-import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
 import androidx.activity.viewModels
+import androidx.appcompat.app.AppCompatActivity
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.lifecycleScope
+import androidx.lifecycle.repeatOnLifecycle
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.launch
 
 class MainActivity : AppCompatActivity() {
 
@@ -14,8 +19,25 @@ class MainActivity : AppCompatActivity() {
         val view = layoutInflater.inflate(R.layout.activity_main, null) as CatsView
         setContentView(view)
 
-        catsViewModel.catsLiveData.observe(this){
-            view.populate(it)
+        lifecycleScope.launch {
+            repeatOnLifecycle(Lifecycle.State.STARTED) {
+                catsViewModel.catsStateFlow.collect { value ->
+                    when (value) {
+                        is Result.Empty -> {
+                            view.showError(value.message)
+                        }
+                        is Result.Error -> {
+                            view.showError(
+                                value.error.message
+                                    ?: "Error occurred while fetching data."
+                            )
+                        }
+                        is Result.Success -> {
+                            view.populate(value.result)
+                        }
+                    }
+                }
+            }
         }
     }
 }

flowcats/src/main/java/otus/homework/flowcats/Result.kt

@@ -0,0 +1,7 @@
+package otus.homework.flowcats
+
+sealed class Result<out T> {
+    data class Empty(val message:String) : Result<Nothing>()
+    data class Success<T>(val result: T) : Result<T>()
+    data class Error(val error: Throwable) : Result<Nothing>()
+}

operators/src/main/java/otus/homework/flow/SampleInteractor.kt

@@ -18,7 +18,11 @@ class SampleInteractor(
      * 6) возвращает результат
      */
     fun task1(): Flow<String> {
-        return flowOf()
+        return sampleRepository.produceNumbers()
+            .map { it * 5 }
+            .filter { it > 20 && it % 2 != 0 }
+            .map { "$it won" }
+            .take(3)
     }
 
     /**
@@ -29,7 +33,15 @@ class SampleInteractor(
      * Если число не делится на 3,5,15 - эмитим само число
      */
     fun task2(): Flow<String> {
-        return flowOf()
+        return sampleRepository.produceNumbers()
+            .transform {
+                emit(it.toString())
+                when {
+                    it % 15 == 0 -> emit("FizzBuzz")
+                    it % 5 == 0 -> emit("Buzz")
+                    it % 3 == 0 -> emit("Fizz")
+                }
+            }
     }
 
     /**
@@ -38,7 +50,9 @@ class SampleInteractor(
      * Если айтемы в одно из флоу кончились то результирующий флоу также должен закончится
      */
     fun task3(): Flow<Pair<String, String>> {
-        return flowOf()
+        return sampleRepository.produceColors()
+            .zip(sampleRepository.produceForms())
+            { i1, i2 -> (i1 to i2) }
     }
 
     /**
@@ -48,6 +62,16 @@ class SampleInteractor(
      * При любом исходе, будь то выброс исключения или успешная отработка функции вызовите метод dotsRepository.completed()
      */
     fun task4(): Flow<Int> {
-        return flowOf()
+        return sampleRepository.produceNumbers()
+            .catch {
+                if (it is IllegalArgumentException) {
+                    emit(-1)
+                } else {
+                    throw it
+                }
+            }
+            .onCompletion {
+                sampleRepository.completed()
+            }
     }
 }