Kotlin, cannot create instance of class Viewmodel

Question

I am new to MVVM architecture, I have tried with different options but still getting same exception "cannot able to create an instance ViewModel". I am using Android Studio Iguana

below is my VideoActivity:

class VideoActivity : AppCompatActivity() {
    private lateinit var viewModel: VideoViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        viewModel = ViewModelProvider(this).get(VideoViewModel::class.java)
        
        val videos= listOf(
            Video(id = 1, url = "url1.mp4"),
            Video(id = 1, url = "url2.mp4"),
            Video(id = 1, url = "url3.mp4"),
            Video(id = 1, url = "url4.mp4"),
            Video(id = 1, url = "url5.mp4"),
        )

        viewModel.downloadVideos(videos)

        viewModel.videos.observe(this) { downloadedVideos ->
            if (downloadedVideos.isNotEmpty()) {
                viewModel.playNextVideo()
            }
        }
    }
}

below is my VideoRepository class

    class VideoRepository(private val context: Context) {
       
        suspend fun downloadVideos(videos: List<Video>): List<Video> {
            val downloadedVideos = mutableListOf<Video>()
            for (video in videos) {
                val filePath = downloadVideo(video.url)
                if (filePath.isNotBlank()) {
                    video.downloadStatus = DownloadStatus.DOWNLOADED
                    video.filePath = filePath
                    downloadedVideos.add(video)
                }
            }
            return downloadedVideos
        }
    
        private suspend fun downloadVideo(videoUrl: String): String = withContext(Dispatchers.IO) {
            try {
                val url = URL(videoUrl)
                val connection = url.openConnection() as HttpURLConnection
                connection.connect()
    
                val inputStream: InputStream = connection.inputStream
                val file = File(context.getExternalFilesDir(Environment.DIRECTORY_MOVIES), "video_${System.currentTimeMillis()}.mp4")
                val outputStream = FileOutputStream(file)
    
                val buffer = ByteArray(1024)
                var bytesRead: Int
                while (inputStream.read(buffer).also { bytesRead = it } != -1) {
                    outputStream.write(buffer, 0, bytesRead)
                }
    
                outputStream.flush()
                outputStream.close()
                inputStream.close()
    
                file.absolutePath
            } catch (e: Exception) {
                e.printStackTrace()
                ""
            }
        }
    
        fun playVideo(video: Video) {
            val videoView = (context as VideoActivity).findViewById<VideoView>(R.id.video_view)
            videoView.setVideoURI(Uri.parse(video.filePath))
            videoView.start()
        }
    }

class VideoViewModel(var repository: VideoRepository) : ViewModel(){

    private val _videos = MutableLiveData<List<Video>>()
    val videos:LiveData<List<Video>> = _videos

    private lateinit var videoView: VideoView

    private var currentVideoIndex = 0
    fun downloadVideos(videos: List<Video>){
        viewModelScope.launch {
            val downloadVideos = repository.downloadVideos(videos)
            _videos.postValue(downloadVideos)
        }
    }

    fun playNextVideo(){
        currentVideoIndex = (currentVideoIndex + 1) % (videos.value?.size ?: 1)
        val video = videos.value?.get(currentVideoIndex)
        video?.let{
            repository.playVideo(it)
        }
    }  
}

App Gradle Dependencies:

implementation(libs.androidx.core.ktx)
implementation(libs.androidx.lifecycle.runtime.ktx)
implementation(libs.androidx.activity.compose)
implementation(platform(libs.androidx.compose.bom))
implementation(libs.androidx.ui)
implementation(libs.androidx.ui.graphics)
implementation(libs.androidx.ui.tooling.preview)
implementation(libs.androidx.material3)

implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.1")
implementation("androidx.lifecycle:lifecycle-livedata-ktx:2.3.1")
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.0")
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.0")
implementation(libs.androidx.appcompat)

Below is the exception which I am getting

Process: com.android, PID: 4717
                                                                                                    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android/com.android.main.VideoActivity}: java.lang.RuntimeException: Cannot create an instance of class com.android.main.VideoViewModel
                                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3825)
                                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3971)
                                                                                                        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101)
                                                                                                        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
                                                                                                        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
                                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2389)
                                                                                                        at android.os.Handler.dispatchMessage(Handler.java:106)
                                                                                                        at android.os.Looper.loopOnce(Looper.java:210)
                                                                                                        at android.os.Looper.loop(Looper.java:299)
                                                                                                        at android.app.ActivityThread.main(ActivityThread.java:8261)
                                                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                                                        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:559)
                                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:954)
                                                                                                    Caused by: java.lang.RuntimeException: Cannot create an instance of class com.android.main.VideoViewModel
                                                                                                        at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.kt:201)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:320)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:302)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:276)
                                                                                                        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:128)
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:184)
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:150)
                                                                                                        at com.android.main.VideoActivity.onCreate(VideoActivity.kt:20)
                                                                                                        at android.app.Activity.performCreate(Activity.java:8516)
                                                                                                        at android.app.Activity.performCreate(Activity.java:8480)
                                                                                                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1418)
                                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3806)
                                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3971) 
                                                                                                        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101) 
                                                                                                        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
                                                                                                        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
                                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2389) 
                                                                                                        at android.os.Handler.dispatchMessage(Handler.java:106) 
                                                                                                        at android.os.Looper.loopOnce(Looper.java:210) 
                                                                                                        at android.os.Looper.loop(Looper.java:299) 
                                                                                                        at android.app.ActivityThread.main(ActivityThread.java:8261) 
                                                                                                        at java.lang.reflect.Method.invoke(Native Method) 
                                                                                                        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:559) 
                                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:954) 
                                                                                                    Caused by: java.lang.NoSuchMethodException: com.android.adbeets.main.VideoViewModel.<init> []
                                                                                                        at java.lang.Class.getConstructor0(Class.java:3325)
                                                                                                        at java.lang.Class.getDeclaredConstructor(Class.java:3063)
                                                                                                        at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.kt:199)
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:320) 
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:302) 
                                                                                                        at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.kt:276) 
                                                                                                        at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.kt:128) 
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:184) 
                                                                                                        at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.kt:150) 
                                                                                                        at com.android.adbeets.main.VideoActivity.onCreate(VideoActivity.kt:20) 
                                                                                                        at android.app.Activity.performCreate(Activity.java:8516) 
                                                                                                        at android.app.Activity.performCreate(Activity.java:8480) 
                                                                                                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1418) 
                                                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3806) 
                                                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3971) 
                                                                                                        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:101) 
                                                                                                        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
                                                                                                        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
                                                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2389) 
                                                                                                        at android.os.Handler.dispatchMessage(Handler.java:106) 
                                                                                                        at android.os.Looper.loopOnce(Looper.java:210) 
                                                                                                        at android.os.Looper.loop(Looper.java:299) 
                                                                                                        at android.app.ActivityThread.main(ActivityThread.java:8261) 
                                                                                                        at java.lang.reflect.Method.invoke(Native Method) 
                                                                                                        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:559) 
                                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:954) 
2024-04-09 12:06:35.424 24478-30209 ActivityManagerWrapper  com.miui.home                        E

Could anyone help me on this issue, Thanks inAdvance

Mustafa Berk · Accepted Answer · 2024-04-09 06:56:31Z

2

Your viewModel definition is an old one, try to use the new approach to initialize your viewModel.

Add these dependencies to your project;

def activity_version = "1.8.2"
implementation "androidx.activity:activity-ktx:$activity_version"

Remove your viewModel = ViewModelProvider(this).get(VideoViewModel::class.java) line

Update your private lateinit var viewModel: VideoViewModel to private val viewModel: VideoViewModel by viewModels()

Hope this helps.

answered Apr 9, 2024 at 6:56

Mustafa Berk

1411 gold badge2 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Naveen Over a year ago

Mustafa,Thanks for your response, when I try to add above dependency getting exception Execution failed for task ':app:checkDebugAarMetadata'. > Could not resolve all files for configuration ':app:debugRuntimeClasspath'. > Could not find activityx.activity:activity-ktx:1.8.2.

tyg Over a year ago

You should copy&paste the artifact from the answer. activityx.activity:activity-ktx is not what was suggested.

Mustafa Berk Over a year ago

Please follow this page to implement the library developer.android.com/jetpack/androidx/releases/activity

Miroslav Hýbler · Accepted Answer · 2024-04-09 09:42:14Z

2

Reason is that default viewModel providers cannot construct viewModel which contains properties in primary constructor (excepts for application class). I would recommend you some DI library (hilt for example).

Solution without DI

If you don't want to implement DI right now just change your viewModel's like this:

class VideoViewModel(
application: Application
) : AndroidViewModel(application) {
   val repository: VideoRepository = VideoRepository(application)
}

This is just quick workaround but i recommend using DI.

Solution with DI

Add plugin into your root build.gradle.kts:

plugins {
  //Plugin is taken from google() repository
  id("com.google.dagger.hilt.android") version "2.51.1" apply false
  
  //Keep in mind to use compatible versions of ksp and kotlin
  id("org.jetbrains.kotlin.android") version "1.9.23" apply false
  id("com.google.devtools.ksp") version "1.9.23-1.0.20" apply false
}

then update your app's build.gradle.kts, keep in mind you have to use same version of hilt:

plugins {
  id("com.google.dagger.hilt.android")
  id("com.google.devtools.ksp")
}

android {
  ...
}

dependencies {
    val hiltVersion = "2.51.1"
    val hiltCompilerVersion = "1.2.0"
    implementation("com.google.dagger:hilt-android:$hiltVersion")
    implementation("androidx.hilt:hilt-common:$hiltCompilerVersion")
    
    //using ksp but it's still possible to use kapt
    ksp("com.google.dagger:hilt-android-compiler:$hiltVersion")
    ksp("androidx.hilt:hilt-compiler:$hiltCompilerVersion")
}

After you sync your gradle you have to adjust your code for dependency injection, follow the docs i mentioned.

Annotate your application class with @HiltAndroidApp and also don't forget to declare it in Manifest.xml:

@HiltAndroidApp
class ExampleApplication : Application() { ... }

Manifest:

<application
    android:name=".ExampleApplication"/>

After that annotate your VideoActivity with @AndroidEntryPoint annotation and update how you are constructing the viewModel:

@AndroidEntryPoint
class VideoActivity : AppCompatActivity() { 
   private val viewModel: VideoViewModel by viewModels()
}

Update your viewModel with annotations to tell the hilt how to construct it:

@HiltViewModel
class VideoViewModel @Inject constructor(
val repository: VideoRepository
) : ViewModel(){ ... }

And for your VideoRepository too to tell the hilt how to construct it:

///In case you want only one single instance of repository
@Singleton
class VideoRepository @Inject constructor(
@ApplicationContext private val context: Context
) { ... }

With this you are able to have clean MVVM architecture using dependency injection for better dependencies management. I didn't explained all the details because it's all in the documentation.

Hope this helps.

edited Apr 9, 2024 at 9:42

answered Apr 9, 2024 at 7:49

Miroslav Hýbler

1,4551 gold badge9 silver badges17 bronze badges

12 Comments

tyg Over a year ago

You should use ksp instead of kapt. Also, you need to annotate the Application with @HiltAndroidApp. And while you're at it you should use the newest hilt version.

Naveen Over a year ago

Thanks for your response, what we need to add in Application class, please do let me know

Miroslav Hýbler Over a year ago

@Naveen I updated the DI solution in my answer. @Leviathan Thanks, didn't know that hilt has support for ksp too.

Naveen Over a year ago

@MiroslavHýbler, thanks for updating the code, I am getting below exception after updating the code java.lang.NoSuchMethodError: 'void org.jetbrains.kotlin.incremental.IncrementalCompilationContext.<init>(org.jetbrains.kotlin.incremental.storage.FileToPathConverter, org.jetbrains.kotlin.incremental.storage.FileToPathConverter, boolean, org.jetbrains.kotlin.incremental.CompilationTransaction, org.jetbrains.kotlin.build.report.ICReporter, boolean, boolean, int, kotlin.jvm.internal.DefaultConstructorMarker)'

Miroslav Hýbler Over a year ago

@Naveen Try clean and rebuild your project, and also make sure to use compatible ksp and kotlin versions, i used newest ones in my answer. I didn't experienced this build crash myself, i believe it's just some temporary crash which can be solved by rebuild, or after clearing Android Studio cache and restart.

|

Collectives™ on Stack Overflow

Kotlin, cannot create instance of class Viewmodel

2 Answers 2

3 Comments

12 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

12 Comments

Your Answer

Sign up or log in

Post as a guest

Related