[ADDED] [#8] ViewModel factory and viewmodel for the layout info activity.

[REFACTO] Activity to use the viewmodel.

Author: hossain-khan

app/build.gradle

@@ -102,6 +102,7 @@ dependencies {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    testImplementation "android.arch.core:core-testing:$rootProject.archComponentVersion"
 }
 
 // ADD THIS AT THE BOTTOM

app/src/main/java/com/hossainkhan/android/demo/layoutpreview/LayoutInfoViewModel.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018 Hossain Khan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hossainkhan.android.demo.layoutpreview
+
+import android.arch.lifecycle.LiveData
+import android.arch.lifecycle.MutableLiveData
+import android.arch.lifecycle.ViewModel
+import android.support.annotation.LayoutRes
+import com.hossainkhan.android.demo.data.AppDataStore
+import com.hossainkhan.android.demo.data.LayoutInformation
+import timber.log.Timber
+
+/**
+ * ViewModel for containing layout information.
+ */
+class LayoutInfoViewModel(private val appDataStore: AppDataStore) : ViewModel() {
+    private val layoutInfoLiveData: MutableLiveData<LayoutInformation> = MutableLiveData()
+
+    val layoutInformation: LiveData<LayoutInformation>
+        get() = layoutInfoLiveData
+
+    /**
+     * Provides layout URL for the currently initialized layout resource id.
+     * @see init
+     */
+    val layoutUrl: String
+        get() = appDataStore.layoutStore.getLayoutUrl(layoutInfoLiveData.value!!.layoutResourceId)
+
+    /**
+     * Indicates if the current screen is being shown for the first time.
+     */
+    val isFirstTime: Boolean
+        get() = appDataStore.shouldshowLayoutInformation(layoutInfoLiveData.value!!.layoutResourceId)
+
+
+    fun init(@LayoutRes layoutResourceId: Int) {
+        val layoutInfo = appDataStore.layoutStore.layoutsInfos[layoutResourceId]!!
+        Timber.d("Loading layout: %s", layoutInfoLiveData)
+
+        layoutInfoLiveData.value = layoutInfo
+    }
+}

app/src/main/java/com/hossainkhan/android/demo/layoutpreview/LayoutPreviewBaseActivity.kt

@@ -16,6 +16,8 @@
 
 package com.hossainkhan.android.demo.layoutpreview
 
+import android.arch.lifecycle.Observer
+import android.arch.lifecycle.ViewModelProvider
 import android.content.Context
 import android.content.Intent
 import android.net.Uri
@@ -28,8 +30,8 @@ import android.view.Menu
 import android.view.MenuItem
 import com.andrognito.flashbar.Flashbar
 import com.hossainkhan.android.demo.R
-import com.hossainkhan.android.demo.data.AppDataStore
 import com.hossainkhan.android.demo.data.LayoutInformation
+import com.hossainkhan.android.demo.viewmodel.LayoutPreviewViewModelFactory
 import dagger.android.AndroidInjection
 import timber.log.Timber
 import javax.inject.Inject
@@ -62,25 +64,36 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
     }
 
     @Inject
-    internal lateinit var appDataStore: AppDataStore
+    internal lateinit var viewModelFactory: LayoutPreviewViewModelFactory
+
+    private lateinit var viewModel: LayoutInfoViewModel
 
-    internal lateinit var layoutInformation: LayoutInformation
     internal var flashbar: Flashbar? = null
 
     override fun onCreate(savedInstanceState: Bundle?) {
         AndroidInjection.inject(this)
         super.onCreate(savedInstanceState)
 
         val layoutResourceId = intent.getIntExtra(BUNDLE_KEY_LAYOUT_RESID, -1)
-        layoutInformation = appDataStore.layoutStore.layoutsInfos[layoutResourceId]!!
-        Timber.d("Loading layout: %s", layoutInformation)
 
         setContentView(layoutResourceId)
 
-        supportActionBar?.title = layoutInformation.title
+        viewModel = ViewModelProvider(this, viewModelFactory)
+                .get(LayoutInfoViewModel::class.java)
+        viewModel.init(layoutResourceId)
+
         supportActionBar?.setDisplayHomeAsUpEnabled(true)
 
-        showLayoutInfo(layoutInformation)
+        viewModel.layoutInformation.observe(this,
+                Observer { layoutInfo ->
+                    Timber.d("Received layout info from LiveData: %s", layoutInfo)
+                    updateActionBar(layoutInfo!!)
+                    showLayoutInfo(layoutInfo)
+                })
+    }
+
+    private fun updateActionBar(layoutInformation: LayoutInformation) {
+        supportActionBar?.title = layoutInformation.title
     }
 
     /**
@@ -115,7 +128,7 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
 
         Timber.d("Flash bar showing: %s", flashbar?.isShown())
         if (flashbar?.isShown() == false) {
-            if (fromUser || appDataStore.shouldshowLayoutInformation(layoutInformation.layoutResourceId)) {
+            if (fromUser || viewModel.isFirstTime) {
                 flashbar?.show()
             }
         } else {
@@ -127,12 +140,11 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
      * Loads currently running layout from Github into chrome web view.
      */
     fun loadLayoutUrl() {
-        val layoutUrl = appDataStore.layoutStore.getLayoutUrl(layoutInformation.layoutResourceId)
         val builder = CustomTabsIntent.Builder()
         builder.setShowTitle(false)
                 .addDefaultShareMenuItem()
         val customTabsIntent = builder.build()
-        customTabsIntent.launchUrl(this, Uri.parse(layoutUrl))
+        customTabsIntent.launchUrl(this, Uri.parse(viewModel.layoutUrl))
     }
 
 
@@ -148,7 +160,7 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
     override fun onOptionsItemSelected(item: MenuItem): Boolean {
         return when (item.itemId) {
             R.id.show_layout_info_menu_item -> {
-                showLayoutInfo(layoutInformation, true)
+                showLayoutInfo(viewModel.layoutInformation.value!!, true)
                 true
             }
             android.R.id.home -> {

app/src/main/java/com/hossainkhan/android/demo/viewmodel/LayoutPreviewViewModelFactory.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2018 Hossain Khan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hossainkhan.android.demo.viewmodel
+
+import android.arch.lifecycle.ViewModel
+import android.arch.lifecycle.ViewModelProvider
+import com.hossainkhan.android.demo.data.AppDataStore
+import com.hossainkhan.android.demo.layoutpreview.LayoutInfoViewModel
+import javax.inject.Inject
+
+class LayoutPreviewViewModelFactory @Inject constructor(
+        private val dataStore: AppDataStore
+
+) : ViewModelProvider.Factory {
+    @Suppress("UNCHECKED_CAST")
+    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
+        return when {
+            modelClass.isAssignableFrom(LayoutInfoViewModel::class.java) ->
+                LayoutInfoViewModel(dataStore) as T
+            else -> throw IllegalArgumentException("Unknown ViewModel class")
+        }
+    }
+}

app/src/test/java/com/hossainkhan/android/demo/layoutpreview/LayoutInfoViewModelTest.kt

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2018 Hossain Khan
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.hossainkhan.android.demo.layoutpreview
+
+import android.content.SharedPreferences
+import android.content.res.Resources
+import com.hossainkhan.android.demo.data.AppDataStore
+import com.hossainkhan.android.demo.data.LayoutDataStore
+import org.junit.Test
+
+import org.junit.Assert.*
+import org.junit.Before
+import org.mockito.Mockito.mock
+import android.arch.core.executor.testing.InstantTaskExecutorRule
+import org.junit.rules.TestRule
+import org.junit.Rule
+
+
+class LayoutInfoViewModelTest {
+    /**
+     * Uses rule to test LiveData
+     *
+     * References:
+     *  - https://medium.com/pxhouse/unit-testing-with-mutablelivedata-22b3283a7819
+     *  - https://stackoverflow.com/questions/29945087/kotlin-and-new-activitytestrule-the-rule-must-be-public
+     */
+    @get:Rule
+    val rule: TestRule = InstantTaskExecutorRule()
+
+    private val resources: Resources = mock(Resources::class.java)
+    private val preferences: SharedPreferences = mock(SharedPreferences::class.java)
+    private val layoutStore = LayoutDataStore(resources)
+
+    private val mockLayoutId = layoutStore.supportedLayoutInfos.first().layoutResourceId
+
+    lateinit var sut: LayoutInfoViewModel
+
+    @Before
+    fun setup() {
+        sut = LayoutInfoViewModel(AppDataStore(preferences, layoutStore))
+    }
+
+    @Test
+    fun getLayoutInformation_givenLayoutId_providesLayoutInformationViaLiveData() {
+        sut.init(mockLayoutId)
+
+        assertEquals(layoutStore.layoutsInfos[mockLayoutId], sut.layoutInformation.value)
+    }
+
+}