CODEWITHSUNDEEP
androidkotlinviewmodel
Toni Joe
Toni Joe

Reputation: 8417

'by viewModels()' Kotlin property delegate unresolved reference

I'm trying to implement viewmodel with kotlin. First I added the needed dependecies:

implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'androidx.core:core-ktx:1.2.0'
// ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0"
// Annotation processor
kapt "androidx.lifecycle:lifecycle-compiler:2.2.0"

Then I created a simple viewmodel:

class MyViewModel: ViewModel() {
    val greeting = "Hello World"
}

But when I tried to access the view model from the activity with kotlin property delegate:

val model by viewModels<MyViewModel>()

The compiler does not resolve viewModels. I don't know what the problem is. Did I miss something?

Upvotes: 80

Views: 48651

Answers (11)

Jeff1992.
Jeff1992.

Reputation: 1

For me, the only solution was to go to-> File->Repair IDE, then in the notification, click on More->Rescan Project Indexes, then Reopen Project.

That's not the definitive solution but only in that way the IDE recognizes viewModels() again, until a new gradle sync.

I think this issue is not related to the dependencies, is more about a bug in the IDE.

Upvotes: 0

devu mani
devu mani

Reputation: 377

For me, I worked a lot to make this work by trying different different imports. But none of them worked. After that I understood, that it was not the imports, it was the place I was trying to use by viewModels that was causing the problem.

You can use the same syntax in "onCreate" function, pass the view model to another composable function, and use it there without any problem, like mentioned in this solution

https://stackoverflow.com/a/73091010/8860360

Another workaround is like this, thus you don't need to pass the viewmodel to function:

ie, instead of this val model by viewModels<MyViewModel>()

you should use this val model: MyViewModel = viewModel() inside a composable function

Upvotes: 0

Ahmad Reza Enshaee
Ahmad Reza Enshaee

Reputation: 437

To people who already has declared the fragment-ktx or the activity-ktx in their build file but still the IDE won't find the viewModels() or activityViewModels() for them, neither in the Fragments nor the Activities: Restart your Android Studio. If it didn't work, restart your computer. It worked for me.

UPDATE

Didn't work for long. Although I realized the import statement doesn't show any errors and it's just the statement that show the error, but even with that, the code compiles fine.

Upvotes: 0

nick
nick

Reputation: 11

See if you have navigation-fragment dependency added.

implementation("androidx.navigation:navigation-fragment-ktx:2.7.0")
implementation("androidx.navigation:navigation-ui-ktx:2.7.0")

Having this one and activity/fragment-ktx additionaly made viewModels delegate unavailable for me so I got rid of both of them and only left the navigation artifact.

Upvotes: 1

Yasir Ali
Yasir Ali

Reputation: 71

It depends, on how you are using ViewModel. If you don't use fragments, this is enough to resolve "Unresolved reference: viewModels" for activity.

// ViewModel
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.5.1'
implementation 'androidx.activity:activity-ktx:1.6.1' 

// is to add the dependency on Fragment
implementation 'androidx.fragment:fragment-ktx:1.2.5'

// is to add the dependency on Activity
implementation 'androidx.activity:activity-ktx:1.1.0'

Upvotes: 5

Mr. Techie
Mr. Techie

Reputation: 886

For me, I was having the following dependencies:

implementation 'androidx.activity:activity-compose:1.5.0'

but still I faced this same error.

The reason was that by viewModels() must be called inside the onCreate():

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val customViewModel: MyViewModel by viewModels()

        setContent {
            AppTheme {
                Surface() {
                    MyApp(customViewModel = customViewModel)
                }
            }
        }
    }
}

and not in any other composable function. But I was trying to calling it from MyApp() composable function. Hence the error.

Upvotes: 4

DJ256
DJ256

Reputation: 101

In my case, I was just using the wrong type of Activity. I had an android.app.Activity instead of an androidx.appcompat.app.AppCompatActivity.viewModels() is only available in the latter.

Upvotes: 1

Pratik Dodiya
Pratik Dodiya

Reputation: 2687

Resolved this error, using below dependency in module-level build.gradle

implementation 'androidx.navigation:navigation-fragment-ktx:2.3.5'
implementation 'androidx.navigation:navigation-ui-ktx:2.3.5'

OR

implementation 'androidx.lifecycle:lifecycle-extensions-ktx:2.2.0'
implementation 'androidx.activity:activity-ktx:1.4.0'
implementation 'androidx.fragment:fragment-ktx:1.3.6'

I have also added below dependency to implement ViewModel in Kotlin

implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.1'
implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.3.1'
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'

My module-level build.gradle start as per below

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

Upvotes: 6

Adarsh Dhakad
Adarsh Dhakad

Reputation: 407

For me the solution above this not work.

Add this dependency: :

implementation 'androidx.navigation:navigation-ui-ktx:2.3.5'

Add This dependency :

 implementation "androidx.lifecycle:lifecycleviewmodel:2.2.0"

Upvotes: 3

IR42
IR42

Reputation: 9732

Add these dependencies:

implementation "androidx.activity:activity-ktx:$activity_version"
implementation "androidx.fragment:fragment-ktx:$fragment_version"

You can find the latest versions of libraries here:

https://developer.android.com/jetpack/androidx/releases/activity

https://developer.android.com/jetpack/androidx/releases/fragment

Upvotes: 135

Thiago
Thiago

Reputation: 13302

For me the solution above this not work.

I needed to import :

implementation 'androidx.navigation:navigation-fragment-ktx:2.3.5'

Upvotes: 18

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