[UPDATE] Using dagger multi binding to inject ViewModels

app/src/main/java/com/hossainkhan/android/demo/di/ApplicationModule.kt

@@ -30,7 +30,7 @@ import dagger.Module
  *
  * @see DemoApplicationComponent
  */
-@Module
+@Module(includes = [ViewModelModule::class])
 abstract class ApplicationModule {
     //expose Application as an injectable context
     @Binds

app/src/main/java/com/hossainkhan/android/demo/di/ViewModelKey.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) 2019 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.di
+
+import androidx.lifecycle.ViewModel
+import dagger.MapKey
+import kotlin.reflect.KClass
+
+/**
+ * See https://dagger.dev/multibindings.html
+ */
+@MustBeDocumented
+@Target(
+    AnnotationTarget.FUNCTION,
+    AnnotationTarget.PROPERTY_GETTER,
+    AnnotationTarget.PROPERTY_SETTER
+)
+@Retention(AnnotationRetention.RUNTIME)
+@MapKey
+annotation class ViewModelKey(val value: KClass<out ViewModel>)

app/src/main/java/com/hossainkhan/android/demo/di/ViewModelModule.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2019 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.di
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import com.hossainkhan.android.demo.ui.browse.LayoutBrowseViewModel
+import com.hossainkhan.android.demo.ui.layoutpreview.LayoutInfoViewModel
+import com.hossainkhan.android.demo.viewmodel.ViewModelProviderFactory
+import dagger.Binds
+import dagger.Module
+import dagger.multibindings.IntoMap
+
+/**
+ * Uses dagger multi-binding to provide [ViewModel] instances used in the app.
+ *
+ * @see <a href="https://dagger.dev/multibindings">Multibindings</a>
+ */
+@Suppress("unused")
+@Module
+abstract class ViewModelModule {
+    @Binds
+    @IntoMap
+    @ViewModelKey(LayoutBrowseViewModel::class)
+    abstract fun bindLayoutBrowserViewModel(layoutBrowseViewModel: LayoutBrowseViewModel): ViewModel
+
+    @Binds
+    @IntoMap
+    @ViewModelKey(LayoutInfoViewModel::class)
+    abstract fun bindLayoutInfoViewModel(layoutInfoViewModel: LayoutInfoViewModel): ViewModel
+
+    @Binds
+    abstract fun bindViewModelFactory(factory: ViewModelProviderFactory): ViewModelProvider.Factory
+}

app/src/main/java/com/hossainkhan/android/demo/ui/browse/LayoutBrowseActivity.kt

@@ -22,7 +22,7 @@ import androidx.lifecycle.ViewModelProviders
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import com.hossainkhan.android.demo.R
-import com.hossainkhan.android.demo.viewmodel.LayoutPreviewViewModelFactory
+import com.hossainkhan.android.demo.viewmodel.ViewModelProviderFactory
 import dagger.android.AndroidInjection
 import javax.inject.Inject
 
@@ -31,7 +31,7 @@ import javax.inject.Inject
  */
 class LayoutBrowseActivity : AppCompatActivity() {
     @Inject
-    internal lateinit var viewModelFactory: LayoutPreviewViewModelFactory
+    internal lateinit var viewModelFactory: ViewModelProviderFactory
 
     private lateinit var recyclerView: RecyclerView
     private lateinit var viewAdapter: RecyclerView.Adapter<*>

app/src/main/java/com/hossainkhan/android/demo/ui/browse/LayoutBrowseViewModel.kt

@@ -30,8 +30,9 @@ import com.hossainkhan.android.demo.ui.layoutpreview.LayoutGuidelineBarrierActiv
 import com.hossainkhan.android.demo.ui.layoutpreview.LayoutGuidelineGroupActivity
 import com.hossainkhan.android.demo.ui.layoutpreview.LayoutVisibilityGoneActivity
 import timber.log.Timber
+import javax.inject.Inject
 
-class LayoutBrowseViewModel(
+class LayoutBrowseViewModel @Inject constructor(
         appDataStore: AppDataStore,
         private val browseNavigator: LayoutBrowseNavigator) : ViewModel() {
 

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

@@ -23,11 +23,12 @@ import androidx.annotation.LayoutRes
 import com.hossainkhan.android.demo.data.AppDataStore
 import com.hossainkhan.android.demo.data.LayoutInformation
 import timber.log.Timber
+import javax.inject.Inject
 
 /**
  * ViewModel for containing layout information.
  */
-class LayoutInfoViewModel(private val appDataStore: AppDataStore) : ViewModel() {
+class LayoutInfoViewModel @Inject constructor(private val appDataStore: AppDataStore) : ViewModel() {
     private val layoutInfoLiveData: MutableLiveData<LayoutInformation> = MutableLiveData()
 
     val layoutInformation: LiveData<LayoutInformation>

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

@@ -16,22 +16,20 @@
 
 package com.hossainkhan.android.demo.ui.layoutpreview
 
-import androidx.lifecycle.Observer
-import androidx.lifecycle.ViewModelProvider
 import android.content.Context
 import android.content.Intent
-import android.net.Uri
 import android.os.Bundle
-import androidx.annotation.LayoutRes
-import androidx.browser.customtabs.CustomTabsIntent
-import androidx.core.app.NavUtils
-import androidx.appcompat.app.AppCompatActivity
 import android.view.Menu
 import android.view.MenuItem
+import androidx.annotation.LayoutRes
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.app.NavUtils
+import androidx.lifecycle.Observer
+import androidx.lifecycle.ViewModelProvider
 import com.hossainkhan.android.demo.R
 import com.hossainkhan.android.demo.data.LayoutInformation
 import com.hossainkhan.android.demo.ui.dialog.LayoutInfoDialog
-import com.hossainkhan.android.demo.viewmodel.LayoutPreviewViewModelFactory
+import com.hossainkhan.android.demo.viewmodel.ViewModelProviderFactory
 import dagger.android.AndroidInjection
 import timber.log.Timber
 import javax.inject.Inject
@@ -77,7 +75,7 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
     }
 
     @Inject
-    internal lateinit var viewModelFactory: LayoutPreviewViewModelFactory
+    internal lateinit var viewModelFactory: ViewModelProviderFactory
 
     private lateinit var viewModel: LayoutInfoViewModel
 
@@ -123,9 +121,7 @@ open class LayoutPreviewBaseActivity : AppCompatActivity() {
         Timber.d("Layout info is showing: %s", infoDialog?.isVisible)
         if (infoDialog?.isVisible == false) {
             if (fromUser || viewModel.isFirstTime) {
-                infoDialog?.let {
-                    it.show(supportFragmentManager, "dialog")
-                }
+                infoDialog?.show(supportFragmentManager, "dialog")
             }
         } else {
             infoDialog?.dismiss()

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

@@ -0,0 +1,47 @@
+/*
+ * 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 androidx.lifecycle.ViewModel
+import androidx.lifecycle.ViewModelProvider
+import javax.inject.Inject
+import javax.inject.Provider
+import javax.inject.Singleton
+import com.hossainkhan.android.demo.di.ViewModelModule
+/**
+ * The [ViewModelProvider.Factory] to get instance of all viewmodels using Dagger multi-binding.
+ *
+ *
+ * @see <a href="https://dagger.dev/multibindings">Multibindings</a>
+ * @see [ViewModelModule]
+ */
+@Singleton
+class ViewModelProviderFactory @Inject constructor(
+        private val creators: Map<Class<out ViewModel>, @JvmSuppressWildcards Provider<ViewModel>>
+) : ViewModelProvider.Factory {
+    override fun <T : ViewModel> create(modelClass: Class<T>): T {
+        val creator = creators[modelClass] ?: creators.entries.firstOrNull {
+            modelClass.isAssignableFrom(it.key)
+        }?.value ?: throw IllegalArgumentException("Unknown view model class $modelClass. Must be added to map first.")
+        try {
+            @Suppress("UNCHECKED_CAST")
+            return creator.get() as T
+        } catch (e: Exception) {
+            throw RuntimeException(e)
+        }
+    }
+}