70

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?

Toni Joe
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8 Answers8

117

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

Roland
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IR42
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16

For me the solution above this not work.

I needed to import :

implementation 'androidx.navigation:navigation-fragment-ktx:2.3.5'
Thiago
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6

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'
}
Pratik Dodiya
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4

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'
pz64_
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Yasir Ali
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3

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"
Nadim Ansari
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Adarsh Dhakad
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1

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.

Mr. Techie
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0

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.

DJ256
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0

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.

nick
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