Fix part of #4: Introduce domain module

.gitignore

@@ -8,6 +8,7 @@
 /.idea/navEditor.xml
 /.idea/assetWizardSettings.xml
 app/build
+domain/build
 model/build
 utility/build
 .DS_Store

app/build.gradle

@@ -1,65 +1,71 @@
 apply plugin: 'com.android.application'
-
 apply plugin: 'kotlin-android'
-
 apply plugin: 'kotlin-android-extensions'
 
 android {
-    compileSdkVersion 29
-    buildToolsVersion "29.0.1"
-    defaultConfig {
-        applicationId "org.oppia.app"
-        minSdkVersion 16
-        targetSdkVersion 28
-        versionCode 1
-        versionName "1.0"
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+  compileSdkVersion 29
+  buildToolsVersion "29.0.1"
+  defaultConfig {
+    applicationId "org.oppia.app"
+    minSdkVersion 16
+    targetSdkVersion 28
+    versionCode 1
+    versionName "1.0"
+    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+  }
+  buildTypes {
+    release {
+      minifyEnabled false
+      proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
     }
-    buildTypes {
-        release {
-            minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
-        }
-    }
-    testOptions {
-        unitTests {
-            includeAndroidResources = true
-        }
+  }
+  dataBinding {
+    enabled = true
+  }
+  testOptions {
+    unitTests {
+      includeAndroidResources = true
     }
+  }
 
-    // https://proandroiddev.com/isolated-fragments-unit-tests-that-run-both-instrumented-and-on-the-jvm-with-the-same-source-code-283db2e9be5d
-    sourceSets {
-        androidTest {
-            java.srcDirs += "src/sharedTest/java"
-            kotlin.srcDirs += "src/sharedTest/java"
-        }
-        test {
-            java.srcDirs += "src/sharedTest/java"
-            kotlin.srcDirs += "src/sharedTest/java"
-        }
+  // https://proandroiddev.com/isolated-fragments-unit-tests-that-run-both-instrumented-and-on-the-jvm-with-the-same-source-code-283db2e9be5d
+  sourceSets {
+    androidTest {
+      java.srcDirs += "src/sharedTest/java"
+      kotlin.srcDirs += "src/sharedTest/java"
+    }
+    test {
+      java.srcDirs += "src/sharedTest/java"
+      kotlin.srcDirs += "src/sharedTest/java"
     }
+  }
 }
 
 dependencies {
-    implementation fileTree(dir: 'libs', include: ['*.jar'])
-    implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-    implementation 'androidx.appcompat:appcompat:1.0.2'
-    implementation 'androidx.core:core-ktx:1.0.2'
-    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
-    api 'com.google.guava:guava:28.0-android'
-
-    testImplementation 'androidx.test:core:1.2.0'
-    testImplementation 'androidx.test.ext:junit:1.1.1'
-    testImplementation 'org.robolectric:robolectric:4.3'
-    testImplementation "com.google.truth:truth:0.43"
-    testImplementation 'androidx.test.espresso:espresso-core:3.2.0'
-
-    androidTestImplementation 'androidx.test:core:1.2.0'
-    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
-    androidTestImplementation 'androidx.test:runner:1.2.0'
-    androidTestImplementation "com.google.truth:truth:0.43"
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
-
-    implementation project(":model")
-    implementation project(":utility")
+  implementation fileTree(dir: 'libs', include: ['*.jar'])
+  implementation(
+      'android.arch.lifecycle:extensions:1.1.1',
+      'androidx.appcompat:appcompat:1.0.2',
+      'androidx.constraintlayout:constraintlayout:1.1.3',
+      'androidx.core:core-ktx:1.0.2',
+      'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0-alpha03',
+      "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version",
+  )
+  testImplementation(
+      'androidx.test:core:1.2.0',
+      'androidx.test.espresso:espresso-core:3.2.0',
+      'androidx.test.ext:junit:1.1.1',
+      'com.google.truth:truth:0.43',
+      'org.robolectric:robolectric:4.3',
+  )
+  androidTestImplementation(
+      'androidx.test:core:1.2.0',
+      'androidx.test.espresso:espresso-core:3.2.0',
+      'androidx.test.ext:junit:1.1.1',
+      'androidx.test:runner:1.2.0',
+      'com.google.truth:truth:0.43',
+  )
+  implementation project(":model")
+  implementation project(":domain")
+  implementation project(":utility")
 }

app/src/main/java/org/oppia/app/HomeActivity.kt

@@ -1,52 +1,14 @@
 package org.oppia.app
 
-import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
-import android.util.Log
-import android.widget.TextView
-import com.google.common.util.concurrent.FutureCallback
-import com.google.common.util.concurrent.Futures
-import com.google.common.util.concurrent.ListenableFuture
-import com.google.common.util.concurrent.MoreExecutors.directExecutor
-import org.oppia.app.model.UserAppHistory
-import org.oppia.util.data.AsyncDataSource
+import androidx.appcompat.app.AppCompatActivity
 
 /** The central activity for all users entering the app. */
 class HomeActivity : AppCompatActivity() {
 
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)
     setContentView(R.layout.home_activity)
-  }
-
-  override fun onStart() {
-    super.onStart()
-    // TODO(BenHenning): Convert this to LiveData rather than risk an async operation completing outside of the
-    // activity's lifecycle. Also, a directExecutor() in this context could be a really bad idea if it isn't the main
-    // thread.
-    Futures.addCallback(getUserAppHistory().pendingOperation, object: FutureCallback<UserAppHistory> {
-      override fun onSuccess(result: UserAppHistory?) {
-        if (result != null && result.alreadyOpenedApp) {
-          getWelcomeTextView().setText(R.string.welcome_back_text)
-        }
-      }
-
-      override fun onFailure(t: Throwable) {
-        // TODO(BenHenning): Replace this log statement with a clearer logging API.
-        Log.e("HomeActivity", "Failed to retrieve user app history", t)
-      }
-    }, directExecutor())
-  }
-
-  private fun getWelcomeTextView(): TextView {
-    return findViewById(R.id.welcome_text_view)
-  }
-
-  private fun getUserAppHistory(): AsyncDataSource<UserAppHistory> {
-    // TODO(BenHenning): Retrieve this from a domain provider.
-    return object: AsyncDataSource<UserAppHistory> {
-      override val pendingOperation: ListenableFuture<UserAppHistory>
-        get() = Futures.immediateFuture(UserAppHistory.newBuilder().setAlreadyOpenedApp(false).build())
-    }
+    supportFragmentManager.beginTransaction().add(R.id.home_fragment_placeholder, HomeFragment()).commitNow()
   }
 }

app/src/main/java/org/oppia/app/HomeFragment.kt

@@ -0,0 +1,55 @@
+package org.oppia.app
+
+import android.os.Bundle
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Transformations
+import androidx.lifecycle.ViewModelProviders
+import org.oppia.app.databinding.HomeFragmentBinding
+import org.oppia.app.model.UserAppHistory
+import org.oppia.domain.UserAppHistoryController
+import org.oppia.util.data.AsyncResult
+
+/** Fragment that contains an introduction to the app. */
+class HomeFragment : Fragment() {
+  private val userAppHistoryController = UserAppHistoryController()
+
+  override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
+    val binding = HomeFragmentBinding.inflate(inflater, container, /* attachToRoot= */ false)
+    val viewModel = getUserAppHistoryViewModel()
+    val appUserHistory = getUserAppHistory()
+    viewModel.userAppHistoryLiveData = appUserHistory
+    // NB: Both the view model and lifecycle owner must be set in order to correctly bind LiveData elements to
+    // data-bound view models.
+    binding.let {
+      it.viewModel = viewModel
+      it.lifecycleOwner = this
+    }
+
+    // TODO(#70): Mark that the user opened the app once it's persisted to disk.
+
+    return binding.root
+  }
+
+  private fun getUserAppHistoryViewModel(): UserAppHistoryViewModel {
+    return ViewModelProviders.of(this).get(UserAppHistoryViewModel::class.java)
+  }
+
+  private fun getUserAppHistory(): LiveData<UserAppHistory> {
+    // If there's an error loading the data, assume the default.
+    return Transformations.map(
+      userAppHistoryController.getUserAppHistory()
+    ) { result: AsyncResult<UserAppHistory> -> processUserAppHistoryResult(result) }
+  }
+
+  private fun processUserAppHistoryResult(appHistoryResult: AsyncResult<UserAppHistory>): UserAppHistory {
+    if (appHistoryResult.isFailure()) {
+      Log.e("HomeFragment", "Failed to retrieve user app history", appHistoryResult.error)
+    }
+    return appHistoryResult.getOrDefault(UserAppHistory.getDefaultInstance())
+  }
+}

app/src/main/java/org/oppia/app/UserAppHistoryViewModel.kt

@@ -0,0 +1,10 @@
+package org.oppia.app
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.ViewModel
+import org.oppia.app.model.UserAppHistory
+
+/** [ViewModel] for user app usage history. */
+class UserAppHistoryViewModel: ViewModel() {
+  var userAppHistoryLiveData: LiveData<UserAppHistory>? = null
+}

app/src/main/res/layout/home_activity.xml

@@ -1,20 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout
+<FrameLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
-  xmlns:app="http://schemas.android.com/apk/res-auto"
   xmlns:tools="http://schemas.android.com/tools"
+  android:id="@+id/home_fragment_placeholder"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
-  tools:context=".HomeActivity">
-
-  <TextView
-    android:id="@+id/welcome_text_view"
-    android:layout_width="wrap_content"
-    android:layout_height="wrap_content"
-    android:text="@string/welcome_text"
-    app:layout_constraintBottom_toBottomOf="parent"
-    app:layout_constraintLeft_toLeftOf="parent"
-    app:layout_constraintRight_toRightOf="parent"
-    app:layout_constraintTop_toTopOf="parent" />
-
-</androidx.constraintlayout.widget.ConstraintLayout>
+  tools:context=".HomeActivity" />

app/src/main/res/layout/home_fragment.xml

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout
+  xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:app="http://schemas.android.com/apk/res-auto">
+
+  <data>
+    <import type="org.oppia.app.R"/>
+    <variable
+      name="viewModel"
+      type="org.oppia.app.UserAppHistoryViewModel"/>
+  </data>
+
+  <androidx.constraintlayout.widget.ConstraintLayout
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView
+      android:id="@+id/welcome_text_view"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:text="@{viewModel.userAppHistoryLiveData.getAlreadyOpenedApp() ? R.string.welcome_back_text : R.string.welcome_text}"
+      app:layout_constraintBottom_toBottomOf="parent"
+      app:layout_constraintLeft_toLeftOf="parent"
+      app:layout_constraintRight_toRightOf="parent"
+      app:layout_constraintTop_toTopOf="parent"/>
+
+  </androidx.constraintlayout.widget.ConstraintLayout>
+</layout>

build.gradle

@@ -1,27 +1,27 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.3.41'
-    repositories {
-        google()
-        jcenter()
-    }
-    dependencies {
-        classpath 'com.android.tools.build:gradle:3.4.2'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.10'
-        // NOTE: Do not place your application dependencies here; they belong
-        // in the individual module build.gradle files
-    }
+  ext.kotlin_version = '1.3.41'
+  repositories {
+    google()
+    jcenter()
+  }
+  dependencies {
+    classpath 'com.android.tools.build:gradle:3.4.2'
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.10'
+    // NOTE: Do not place your application dependencies here; they belong
+    // in the individual module build.gradle files
+  }
 }
 
 allprojects {
-    repositories {
-        google()
-        jcenter()
-    }
+  repositories {
+    google()
+    jcenter()
+  }
 }
 
 task clean(type: Delete) {
-    delete rootProject.buildDir
+  delete rootProject.buildDir
 }