Prepare UseCase4

Author: LukasLechnerDev

app/src/main/AndroidManifest.xml

@@ -107,6 +107,10 @@
             android:name=".usecases.flow.usecase3.FlowUseCase3Activity"
             android:exported="true" />
 
+        <activity
+            android:name=".usecases.flow.usecase4.FlowUseCase4Activity"
+            android:exported="true" />
+
     </application>
 
 </manifest>

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

@@ -26,6 +26,7 @@ import com.lukaslechner.coroutineusecasesonandroid.usecases.coroutines.usecase9.
 import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase1.FlowUseCase1Activity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase2.FlowUseCase2Activity
 import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase3.FlowUseCase3Activity
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4.FlowUseCase4Activity
 import kotlinx.parcelize.Parcelize
 
 @Parcelize
@@ -152,6 +153,7 @@ private val coroutinesUseCases =
 const val flowUseCase1Description = "#1 Flow Basics"
 const val flowUseCase2Description = "#2 Basic Intermediate operators"
 const val flowUseCase3Description = "#3 Exception Handling"
+const val flowUseCase4Description = "#4 Exposing Flows in the ViewModel"
 
 private val flowUseCases =
     UseCaseCategory(
@@ -166,6 +168,9 @@ private val flowUseCases =
             ),UseCase(
                 flowUseCase3Description,
                 FlowUseCase3Activity::class.java
+            ),UseCase(
+                flowUseCase4Description,
+                FlowUseCase4Activity::class.java
             )
         )
     )

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/FlowUseCase4Activity.kt

@@ -0,0 +1,56 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import android.os.Bundle
+import androidx.activity.viewModels
+import com.lukaslechner.coroutineusecasesonandroid.base.BaseActivity
+import com.lukaslechner.coroutineusecasesonandroid.base.flowUseCase4Description
+import com.lukaslechner.coroutineusecasesonandroid.databinding.ActivityFlowUsecase1Binding
+import com.lukaslechner.coroutineusecasesonandroid.utils.setGone
+import com.lukaslechner.coroutineusecasesonandroid.utils.setVisible
+import com.lukaslechner.coroutineusecasesonandroid.utils.toast
+import org.joda.time.LocalDateTime
+import org.joda.time.format.DateTimeFormat
+
+class FlowUseCase4Activity : BaseActivity() {
+
+    private val binding by lazy { ActivityFlowUsecase1Binding.inflate(layoutInflater) }
+    private val adapter = StockAdapter()
+
+    private val viewModel: FlowUseCase4ViewModel by viewModels {
+        ViewModelFactory(NetworkStockPriceDataSource(mockApi(applicationContext)))
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(binding.root)
+        binding.recyclerView.adapter = adapter
+
+        viewModel.currentStockPriceAsLiveData.observe(this) { uiState ->
+            if (uiState != null) {
+                render(uiState)
+            }
+        }
+    }
+
+    private fun render(uiState: UiState) {
+        when (uiState) {
+            is UiState.Loading -> {
+                binding.progressBar.setVisible()
+                binding.recyclerView.setGone()
+            }
+            is UiState.Success -> {
+                binding.recyclerView.setVisible()
+                binding.lastUpdateTime.text =
+                    "lastUpdateTime: ${LocalDateTime.now().toString(DateTimeFormat.fullTime())}"
+                adapter.stockList = uiState.stockList
+                binding.progressBar.setGone()
+            }
+            is UiState.Error -> {
+                toast(uiState.message)
+                binding.progressBar.setGone()
+            }
+        }
+    }
+
+    override fun getToolbarTitle() = flowUseCase4Description
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/FlowUseCase4ViewModel.kt

@@ -0,0 +1,27 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.asLiveData
+import com.lukaslechner.coroutineusecasesonandroid.base.BaseViewModel
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onCompletion
+import kotlinx.coroutines.flow.onStart
+import timber.log.Timber
+
+class FlowUseCase4ViewModel(
+    stockPriceDataSource: StockPriceDataSource
+) : BaseViewModel<UiState>() {
+
+    val currentStockPriceAsLiveData: LiveData<UiState> = stockPriceDataSource
+        .latestStockList
+        .map { stockList ->
+            UiState.Success(stockList) as UiState
+        }
+        .onStart {
+            emit(UiState.Loading)
+        }
+        .onCompletion {
+            Timber.tag("Flow").d("Flow has completed.")
+        }
+        .asLiveData()
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/MockApiBehavior.kt

@@ -0,0 +1,18 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import android.content.Context
+import com.google.gson.Gson
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.createFlowMockApi
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.fakeCurrentStockPrices
+import com.lukaslechner.coroutineusecasesonandroid.utils.MockNetworkInterceptor
+
+fun mockApi(context: Context) =
+    createFlowMockApi(
+        MockNetworkInterceptor()
+            .mock(
+                path = "/current-stock-prices",
+                body = { Gson().toJson(fakeCurrentStockPrices(context)) },
+                status = 200,
+                delayInMs = 1500,
+            )
+    )

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/StockAdapter.kt

@@ -0,0 +1,43 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+import com.lukaslechner.coroutineusecasesonandroid.R
+import com.lukaslechner.coroutineusecasesonandroid.databinding.RecyclerviewItemStockBinding
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.Stock
+import java.text.NumberFormat
+
+class StockAdapter: RecyclerView.Adapter<StockAdapter.ViewHolder>() {
+
+    var stockList: List<Stock>? = null
+    set(value) {
+        field = value
+        notifyDataSetChanged()
+    }
+
+    private val formatter: NumberFormat = NumberFormat.getCurrencyInstance()
+
+    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        val binding = RecyclerviewItemStockBinding.bind(view)
+    }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        val view = LayoutInflater.from(parent.context).inflate(R.layout.recyclerview_item_stock, parent, false)
+        return ViewHolder(view)
+    }
+
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) = with(holder.binding){
+        val stock = stockList?.get(position) ?: return@with
+        rank.text = stock.rank.toString()
+        name.text = stock.name
+        val currentPriceFormatted: String = formatter.format(stock.currentPrice)
+        currentPrice.text = currentPriceFormatted
+    }
+
+    override fun getItemCount(): Int {
+        return stockList?.size ?: 0
+    }
+
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/StockPriceDataSource.kt

@@ -0,0 +1,24 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.FlowMockApi
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.Stock
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import timber.log.Timber
+
+interface StockPriceDataSource {
+    val latestStockList: Flow<List<Stock>>
+}
+
+class NetworkStockPriceDataSource(mockApi: FlowMockApi) : StockPriceDataSource {
+
+    override val latestStockList: Flow<List<Stock>> = flow {
+        while (true) {
+            Timber.tag("Flow").d("Fetching current stock prices")
+            val currentStockList = mockApi.getCurrentStockPrices()
+            emit(currentStockList)
+            delay(5_000)
+        }
+    }
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/UiState.kt

@@ -0,0 +1,9 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import com.lukaslechner.coroutineusecasesonandroid.usecases.flow.mock.Stock
+
+sealed class UiState {
+    object Loading : UiState()
+    data class Success(val stockList: List<Stock>) : UiState()
+    data class Error(val message: String) : UiState()
+}

app/src/main/java/com/lukaslechner/coroutineusecasesonandroid/usecases/flow/usecase4/ViewModelFactory.kt

@@ -0,0 +1,13 @@
+package com.lukaslechner.coroutineusecasesonandroid.usecases.flow.usecase4
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+
+class ViewModelFactory(private val stockPriceDataSource: StockPriceDataSource) :
+    ViewModelProvider.Factory {
+
+    override fun <T : ViewModel> create(modelClass: Class<T>): T {
+        return modelClass.getConstructor(StockPriceDataSource::class.java)
+            .newInstance(stockPriceDataSource)
+    }
+}