Cannot create an instance of class ViewModel kotlin

* If placeholders are disabled, onBind will never receive null but as more pages are * loaded, the scrollbars will jitter as new pages are loaded. You should probably disable * scrollbars if you disable placeholders. */ private const val ENABLE_PLACEHOLDERS = true } val allBookmarks = LivePagedListBuilder(dao.allBookmarkByDatetime(), PagedList.Config.Builder() .setPageSize(PAGE_SIZE) .setEnablePlaceholders(ENABLE_PLACEHOLDERS) .build()).build() fun insert(title: String, description: String, datetime: String) = ioThread { dao.insert(Bookmark(id = 0, title = title, description = description, datetime = datetime)) } fun remove(bookmark: Bookmark) = ioThread { dao.delete(bookmark) } } This is from the google samples.. After I want to: class BookmarkListFragment : FirstFragment() { private var viewModel: BookmarkViewModel? = null .. override fun onActivityCreated(savedInstanceState: Bundle?) { super.onActivityCreated(savedInstanceState) viewModel = ViewModelProviders.of(activity!!).get(BookmarkViewModel::class.java) ... And here is the problem: java.lang.RuntimeException: Cannot create an instance of class com.lacas.db.room.BookmarkViewModel Can I use this in a fragment? java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lacas.asd/com.lacas.asd.ui.activities.testtabs.TestTab2Activity}: java.lang.RuntimeException: Cannot create an instance of class com.lacas.asd.db.room.BookmarkViewModel at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2924) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2985) at android.app.ActivityThread.-wrap14(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1635) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6692) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358) Caused by: java.lang.RuntimeException: Cannot create an instance of class com.lacas.asd.db.room.BookmarkViewModel at android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:207) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102) at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:34) at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:29) at kotlin.UnsafeLazyImpl.getValue(Lazy.kt:154) at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.getViewModel(TestTab2Activity.kt) at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.onCreated(TestTab2Activity.kt:45) at com.lacas.asd.base.BasePermissionsActivity.onCreate(BasePermissionsActivity.kt:34) at android.app.Activity.performCreate(Activity.java:6912) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2877) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2985)  at android.app.ActivityThread.-wrap14(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1635)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:154)  at android.app.ActivityThread.main(ActivityThread.java:6692)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)  Caused by: java.lang.reflect.InvocationTargetException at java.lang.reflect.Constructor.newInstance0(Native Method) at java.lang.reflect.Constructor.newInstance(Constructor.java:430) at android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:199) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134)  at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:34)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:29)  at kotlin.UnsafeLazyImpl.getValue(Lazy.kt:154)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.getViewModel(TestTab2Activity.kt)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.onCreated(TestTab2Activity.kt:45)  at com.lacas.asd.base.BasePermissionsActivity.onCreate(BasePermissionsActivity.kt:34)  at android.app.Activity.performCreate(Activity.java:6912)  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2877)  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2985)  at android.app.ActivityThread.-wrap14(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1635)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:154)  at android.app.ActivityThread.main(ActivityThread.java:6692)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)  Caused by: java.lang.RuntimeException: cannot find implementation for com.lacas.asd.db.room.BookmarkDb. BookmarkDb_Impl does not exist at android.arch.persistence.room.Room.getGeneratedImplementation(Room.java:93) at android.arch.persistence.room.RoomDatabase$Builder.build(RoomDatabase.java:630) at com.lacas.asd.db.room.BookmarkDb$Companion.get(BookmarkDb.kt:29) at com.lacas.asd.db.room.BookmarkViewModel.(BookmarkViewModel.kt:14) at java.lang.reflect.Constructor.newInstance0(Native Method)  at java.lang.reflect.Constructor.newInstance(Constructor.java:430)  at android.arch.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:199)  at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134)  at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:34)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity$viewModel$2.invoke(TestTab2Activity.kt:29)  at kotlin.UnsafeLazyImpl.getValue(Lazy.kt:154)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.getViewModel(TestTab2Activity.kt)  at com.lacas.asd.ui.activities.testtabs.TestTab2Activity.onCreated(TestTab2Activity.kt:45)  at com.lacas.asd.base.BasePermissionsActivity.onCreate(BasePermissionsActivity.kt:34)  at android.app.Activity.performCreate(Activity.java:6912)  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2877)  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2985)  at android.app.ActivityThread.-wrap14(ActivityThread.java)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1635)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:154)  at android.app.ActivityThread.main(ActivityThread.java:6692)  at java.lang.reflect.Method.invoke(Native Method)  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)