update(deps) + refactor

Author: hoc081098

app/build.gradle

@@ -31,30 +31,31 @@ android {
         jvmTarget = "1.8"
     }
 
-    viewBinding {
-        enabled = true
+    buildFeatures {
+        viewBinding = true
     }
 
 }
 
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
 
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+
     implementation 'androidx.appcompat:appcompat:1.1.0'
-    implementation 'androidx.core:core-ktx:1.2.0'
+    implementation 'androidx.core:core-ktx:1.3.0'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
-    implementation "androidx.recyclerview:recyclerview:1.2.0-alpha02"
+    implementation 'androidx.recyclerview:recyclerview:1.2.0-alpha03'
     implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0'
     implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0'
-    implementation 'androidx.fragment:fragment-ktx:1.2.3'
+    implementation 'androidx.fragment:fragment-ktx:1.2.4'
     implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.2.0'
 
     // coroutines
-    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.5'
-    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.5'
+    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.6'
+    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.6'
 
-    testImplementation 'junit:junit:4.12'
+    testImplementation 'junit:junit:4.13'
     androidTestImplementation 'androidx.test.ext:junit:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
 }

app/src/main/java/com/hoc/mergeadapter_sample/Data.kt

@@ -4,19 +4,17 @@ import kotlinx.coroutines.delay
 import java.util.concurrent.atomic.AtomicBoolean
 import java.util.concurrent.atomic.AtomicInteger
 
+//region Models
 data class User(
   val uid: Int,
   val name: String,
   val email: String
 )
 
-sealed class LoadingState {
-  object Loading : LoadingState()
-  data class Error(val throwable: Throwable) : LoadingState()
-}
-
 object ApiError : Throwable(message = "Api error")
+//endregion
 
+//region Fake api calling
 suspend fun getUsers(start: Int, limit: Int): List<User> {
   delay(2_000)
 
@@ -34,4 +32,5 @@ suspend fun getUsers(start: Int, limit: Int): List<User> {
 }
 
 private val count = AtomicInteger(0)
-private val throwError = AtomicBoolean(true)
+private val throwError = AtomicBoolean(true)
+//endregion

app/src/main/java/com/hoc/mergeadapter_sample/FooterAdapter.kt

@@ -9,9 +9,10 @@ import androidx.recyclerview.widget.RecyclerView
 import com.hoc.mergeadapter_sample.databinding.ItemFooterBinding
 
 class FooterAdapter(private val onRetry: () -> Unit) :
-  ListAdapter<LoadingState, FooterAdapter.VH>(object : DiffUtil.ItemCallback<LoadingState>() {
-    override fun areItemsTheSame(oldItem: LoadingState, newItem: LoadingState) = true
-    override fun areContentsTheSame(oldItem: LoadingState, newItem: LoadingState) =
+  ListAdapter<PlaceholderState, FooterAdapter.VH>(object :
+    DiffUtil.ItemCallback<PlaceholderState>() {
+    override fun areItemsTheSame(oldItem: PlaceholderState, newItem: PlaceholderState) = true
+    override fun areContentsTheSame(oldItem: PlaceholderState, newItem: PlaceholderState) =
       oldItem == newItem
   }) {
 
@@ -32,23 +33,24 @@ class FooterAdapter(private val onRetry: () -> Unit) :
       }
     }
 
-    fun bind(item: LoadingState) {
+    fun bind(item: PlaceholderState) {
       when (item) {
-        LoadingState.Loading -> {
+        PlaceholderState.Loading -> {
           binding.run {
             buttonRetry.visibility = View.INVISIBLE
             textViewError.visibility = View.INVISIBLE
             progressBar.visibility = View.VISIBLE
           }
         }
-        is LoadingState.Error -> {
+        is PlaceholderState.Failure -> {
           binding.run {
             buttonRetry.visibility = View.VISIBLE
             textViewError.visibility = View.VISIBLE
             textViewError.text = item.throwable.message
             progressBar.visibility = View.INVISIBLE
           }
         }
+        PlaceholderState.Idle -> error("Should not be here!")
       }
     }
   }

app/src/main/java/com/hoc/mergeadapter_sample/MainActivity.kt

@@ -11,15 +11,12 @@ import com.hoc.mergeadapter_sample.databinding.ActivityMainBinding
 import kotlin.LazyThreadSafetyMode.NONE
 
 class MainActivity : AppCompatActivity() {
-  private val vm by viewModels<MainVM>()
+  private val binding by lazy(NONE) { ActivityMainBinding.inflate(layoutInflater) }
+  private val viewModel by viewModels<MainVM>(viewModelFactoryProducer)
 
   private val userAdapter = UserAdapter()
   private val footerAdapter = FooterAdapter(this::onRetry)
 
-  private val binding by lazy(NONE) {
-    ActivityMainBinding.inflate(layoutInflater)
-  }
-
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
     setContentView(binding.root)
@@ -29,28 +26,23 @@ class MainActivity : AppCompatActivity() {
       val linearLayoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)
       layoutManager = linearLayoutManager
       adapter = MergeAdapter(userAdapter, footerAdapter)
+
       addOnScrollListener(object : RecyclerView.OnScrollListener() {
         override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
           if (dy > 0
             && linearLayoutManager.findLastVisibleItemPosition() + VISIBLE_THRESHOLD >= linearLayoutManager.itemCount
           ) {
-            vm.loadNextPage()
+            viewModel.loadNextPage()
           }
         }
       })
     }
 
-
-    vm.loadingStateLiveData.observe(this, Observer {
-      footerAdapter.submitList(it)
-    })
-    vm.userLiveData.observe(this, Observer {
-      userAdapter.submitList(it)
-    })
-    vm.loadNextPage()
+    viewModel.loadingStateLiveData.observe(this, Observer(footerAdapter::submitList))
+    viewModel.userLiveData.observe(this, Observer(userAdapter::submitList))
   }
 
-  private fun onRetry() = vm.retryNextPage()
+  private fun onRetry() = viewModel.retryNextPage()
 
   private companion object {
     private const val VISIBLE_THRESHOLD = 3

app/src/main/java/com/hoc/mergeadapter_sample/MainVM.kt

@@ -2,65 +2,105 @@ package com.hoc.mergeadapter_sample
 
 import androidx.annotation.MainThread
 import androidx.lifecycle.*
+import com.hoc.mergeadapter_sample.PlaceholderState.*
 import kotlinx.coroutines.launch
+import kotlin.LazyThreadSafetyMode.NONE
 
+sealed class PlaceholderState {
+  object Idle : PlaceholderState()
+  object Loading : PlaceholderState()
+  data class Failure(val throwable: Throwable) : PlaceholderState()
+}
 
-class MainVM : ViewModel() {
-  private val usersD = MutableLiveData<List<User>>().apply { value = emptyList() }
-  val userLiveData: LiveData<List<User>> get() = usersD
+class MainVM(private val getUsers: suspend (start: Int, limit: Int) -> List<User>) : ViewModel() {
 
-  private val loadingStateD =
-    MutableLiveData<PlaceholderState>().apply { value = PlaceholderState.Idle }
-  val loadingStateLiveData: LiveData<List<LoadingState>>
-    get() = loadingStateD.map {
-      when (it) {
-        null -> emptyList()
-        PlaceholderState.Idle -> emptyList()
-        PlaceholderState.Loading -> listOf(LoadingState.Loading)
-        is PlaceholderState.Error -> listOf(LoadingState.Error(it.throwable))
-      }
+  //region Private
+  private val usersD by lazy(NONE) {
+    MutableLiveData<List<User>>()
+      .apply { value = emptyList() }
+      .also { loadNextPage() /* load first page when first accessing*/ }
+  }
+  private val loadingStateD = MutableLiveData<PlaceholderState>().apply { value = Idle }
+  private val firstPageStateD = MutableLiveData<PlaceholderState>().apply { value = Idle }
+
+  private var isFirstPage = true
+
+  private val shouldLoadNextPage: Boolean
+    get() = if (isFirstPage) {
+      firstPageStateD.value!! == Idle
+    } else {
+      loadingStateD.value!! == Idle
     }
 
+  private val shouldRetryNextPage: Boolean
+    get() = if (isFirstPage) {
+      firstPageStateD.value!! is Failure
+    } else {
+      loadingStateD.value!! is Failure
+    }
+
+  //endregion
+
+  //region Public LiveDatas
+
+  val userLiveData: LiveData<List<User>> get() = usersD
+
+  val firstPageStateLiveData: LiveData<PlaceholderState> = firstPageStateD
+
+  val loadingStateLiveData: LiveData<List<PlaceholderState>>
+    get() = loadingStateD.map { if (it == Idle) emptyList() else listOf(it) }
+
+  //endregion
+
+  //region Public methods
   @MainThread
   fun loadNextPage() {
-    val state = loadingStateD.value
-    if (state === null || state is PlaceholderState.Idle) {
-      _loadNextPage()
+    if (shouldLoadNextPage) {
+      loadNextPageInternal()
     }
   }
 
   @MainThread
   fun retryNextPage() {
-    if (loadingStateD.value is PlaceholderState.Error) {
-      _loadNextPage()
+    if (shouldRetryNextPage) {
+      loadNextPageInternal()
     }
   }
+  //endregion
 
-  @Suppress("FunctionName")
-  private fun _loadNextPage() {
+  private fun loadNextPageInternal() {
     viewModelScope.launch {
-      loadingStateD.value = PlaceholderState.Loading
+      if (isFirstPage) {
+        firstPageStateD.value = Loading
+      } else {
+        loadingStateD.value = Loading
+      }
 
-      val currentList = usersD.value ?: emptyList()
-      kotlin.runCatching { getUsers(start = currentList.size, limit = LIMIT) }
+      val currentList = usersD.value!!
+
+      runCatching { getUsers(currentList.size, LIMIT) }
         .fold(
           onSuccess = {
+            isFirstPage = currentList.isEmpty()
             usersD.value = currentList + it
-            loadingStateD.value = PlaceholderState.Idle
+
+            if (isFirstPage) {
+              firstPageStateD.value = Idle
+            } else {
+              loadingStateD.value = Idle
+            }
           },
           onFailure = {
-            loadingStateD.value = PlaceholderState.Error(it)
+            if (isFirstPage) {
+              firstPageStateD.value = Failure(it)
+            } else {
+              loadingStateD.value = Failure(it)
+            }
           }
         )
     }
   }
 
-  private sealed class PlaceholderState {
-    object Idle : PlaceholderState()
-    object Loading : PlaceholderState()
-    data class Error(val throwable: Throwable) : PlaceholderState()
-  }
-
   private companion object {
     const val LIMIT = 20
   }

app/src/main/java/com/hoc/mergeadapter_sample/viewModelFactoryProducer.kt

@@ -0,0 +1,16 @@
+package com.hoc.mergeadapter_sample
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+
+val viewModelFactoryProducer: () -> ViewModelProvider.Factory = {
+  object : ViewModelProvider.Factory {
+    @Suppress("UNCHECKED_CAST")
+    override fun <T : ViewModel> create(modelClass: Class<T>): T {
+      if (modelClass == MainVM::class.java) {
+        return MainVM(::getUsers) as T
+      }
+      error("Unknown modelClass: $modelClass")
+    }
+  }
+}

build.gradle

@@ -8,7 +8,7 @@ buildscript {
         maven { url 'https://dl.bintray.com/kotlin/kotlin-eap' }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.1'
+        classpath 'com.android.tools.build:gradle:4.0.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Thu Apr 02 22:05:33 ICT 2020
+#Tue Jun 02 01:10:09 ICT 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip