how to get viewModel by viewModels? (fragment-ktx)

Question

I am working with Single viewModel for the Activity and all of its fragment.

So to initialise viewmodel if have to write this setup code in onActivityCreated of all the fragment's

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProviders.of(activity!!).get(NoteViewModel::class.java)
    }

I was going thorough the Android KTX extension page:(refer here)

and i found i can initialise view model like this:

    // Get a reference to the ViewModel scoped to this Fragment
    val viewModel by viewModels<MyViewModel>()

    // Get a reference to the ViewModel scoped to its Activity
    val viewModel by activityViewModels<MyViewModel>()

So I added below dependency's to my gradle(app):

    //ktx android
    implementation 'androidx.core:core-ktx:1.0.2'
    implementation 'androidx.fragment:fragment-ktx:1.0.0'
    implementation "androidx.lifecycle:lifecycle-extensions:2.0.0"

But when i try to use viewModels/activityViewModels in my application their reference in not found.

I want help in how to use these extension's with some basic example i tried searching for examples haven't found any.

Does your ViewModel take any parameter, like repository or db? — IgorGanapolsky, Oct 29 '19 at 14:22
@IgorGanapolsky yes it does.I am working with single VM shared between all fragment. — Anmol, Oct 30 '19 at 15:29

score 116 · Accepted Answer · edited Jan 05 '23 at 22:35

116

Atlast we we have got stable version.

After moving to implementation 'androidx.fragment:fragment-ktx:1.1.0' i faced another issue.

Compiler Error:

Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6

`build.gradle` (Module `:app`)

compileOptions {
    sourceCompatibility = 1.8
    targetCompatibility = 1.8
}

kotlinOptions {
    jvmTarget = "1.8"
}

reference

After applying all the above the issue's is resolved.

edited Jan 05 '23 at 22:35

Boken

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answered Nov 17 '19 at 08:43

Anmol

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I am working in a multiple module app, Is there a better way then declaring this compileOption into each and every module. – Vikas Pandey Aug 06 '20 at 11:33
@VikasPandey compileOption can be used in the global project build.gradle. – Paul Stelian Apr 19 '21 at 20:54

score 67 · Answer 2 · edited Apr 05 '21 at 10:08

67

try

implementation 'androidx.fragment:fragment-ktx:1.1.0-beta02'

2021 UPDATE

This is no longer in beta. It works with the latest stable version at the time of writing. You will also need to import it in your fragment's Kotlin file.

implementation 'androidx.fragment:fragment-ktx:1.3.2'

import androidx.fragment.app.activityViewModels

edited Apr 05 '21 at 10:08

germanfr

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answered Jul 02 '19 at 13:11

user11729434

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I am not sure if i want to move my project to beta version. – Anmol Jul 03 '19 at 06:29
`by viewModels` can only be called in Fragment, or in activity as well? – IgorGanapolsky Sep 05 '19 at 18:23
29

@IgorGanapolsky This delegate can only be called from the Fragment. But if you add `implementation the "androidx.activity:activity-ktx:1.0.0"` dependency, you can use a similar delegate for the Activity. – Denys Makhov Sep 06 '19 at 09:36
2

@Anmol The version in the answer graduated to Stable recently. You need to be at least on 1.1.0 for `by ViewModels()` – MowDownJoe Sep 16 '19 at 17:31
@MowDownJoe thank for the update and now the issue is fixed – Anmol Nov 17 '19 at 08:44
@DenysMakhov There is no such thing as `androidx.activity:activity-ktx` – IgorGanapolsky Jan 17 '20 at 00:52
@IgorGanapolsky https://developer.android.com/jetpack/androidx/releases/activity – Denys Makhov Jan 17 '20 at 06:32
I got it to work when I used activity-ktx 1.1.0 and extended FragmentActivity() not just Activity() – tonisives Jan 29 '20 at 03:26
3

@DenysMakhov Wrong. `fragment-ktx` works for both activity and fragment. – Dr.jacky Nov 12 '20 at 10:48
1

@Dr.jacky Yes, maybe something has changed in a YEAR. – Denys Makhov Nov 15 '20 at 14:35
10

`by viewModels()` is enough in Activity because you already in the activity, and if you need activity's viewmodel in fragment, use `by activityViewModels()` – Sai Apr 14 '21 at 11:52
@DenysMakhov I had this confusion and gone through the docs to see if there is a separate ktx for Activities :/ – SagaRock101 Jun 12 '21 at 07:27

score 32 · Answer 3 · edited Aug 08 '21 at 16:19

32

I think you need to have this dependency for your activity if you want to use kotlin delegations for viewmodel

//ViewModels delegation extentensions for activity
implementation 'androidx.activity:activity-ktx:1.3.1'

edited Aug 08 '21 at 16:19

Ole Pannier

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answered Aug 08 '21 at 04:57

Bekzhan

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1

Thanks! This was the solution for me. – Cata Nov 14 '21 at 19:07
2

Yep, this is the right answer. Thanks. – Nicolas Mage Feb 26 '22 at 18:15

ONVETI · Answer 4 · 2022-04-29T06:29:23.593

15

UPDATE 2022 APRIL 29

You should use this:

dependencies {
    implementation "androidx.fragment:fragment-ktx:1.4.1"
}

more information:

https://developer.android.com/topic/libraries/architecture/viewmodel#implement

https://developer.android.com/kotlin/ktx#fragment

edited Apr 29 '22 at 06:29

answered Apr 28 '22 at 13:10

ONVETI

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Whilst this may theoretically answer the question, [it would be preferable](//meta.stackexchange.com/q/8259) to include the essential parts of the answer here, and provide the link for reference. i.e. please [edit] your answer to say *why* this is preferred as of April 2022. – Adriaan Apr 28 '22 at 13:22
@Adriaan suggested the right thing. It would be better if the main sample references rather than sharing just web links for the solution. – A S M Sayem May 04 '22 at 19:37

score 3 · Answer 5 · answered Jul 10 '19 at 11:09

3

You use this latest alpha version:

dependencies {
    implementation 'androidx.fragment:fragment-ktx:1.2.0-alpha01'
}

answered Jul 10 '19 at 11:09

Birju Vachhani

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score 3 · Answer 6 · answered Jun 05 '21 at 15:20

Note : This works for Jetpack Compose too

Copy the dependency from HERE

Currently 2021 June 5 the dependency is as below :

dependencies {
    val activity_version = "1.2.3"

    // Java language implementation
    implementation("androidx.activity:activity:$activity_version")
    // Kotlin
    implementation("androidx.activity:activity-ktx:$activity_version")
}

score 3 · Answer 7 · answered Jul 04 '21 at 09:00

3

For googlers: your Activity should inherit AppCompatActivity, not Activity

answered Jul 04 '21 at 09:00

Evgenii Vorobei

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Thank you for noticing that! – Dmitriy Pavlukhin Oct 07 '21 at 16:55
1

Also, make sure you're calling `viewModels()` with a lowercase v, *not* `ViewModels()` – M.Ed Jul 04 '22 at 06:57

score 3 · Answer 8 · answered Jan 12 '23 at 17:38

3

Be sure to use val and not var for your ViewModel property if you get error of cannot find setter.

answered Jan 12 '23 at 17:38

htafoya

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score 2 · Answer 9 · answered Jul 16 '19 at 06:39

2

The extension function viewModels(...) was added in version 1.1.0-alpha03. Therefore, in order to use it in your app you will have to implement the fragment-ktx of versions matching 1.1.0-alpah03 or later.

I just found out about this and so I resorted to using version 1.1.0-rc01 because I didn't want to use alpha/beta versions.

answered Jul 16 '19 at 06:39

sylvery

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can't use it with **1.2.0-alpha02** – IgorGanapolsky Sep 05 '19 at 18:35

midFang · Answer 10 · 2020-12-11T10:35:56.477

You can implementation

implementation 'androidx.fragment:fragment-ktx:1.1.0'

In fact, the BY viewModels implementation in the KTX package looks like this, and you might as well implement an extension function yourself

@MainThread
inline fun <reified VM : ViewModel> ComponentActivity.viewModels(
        noinline factoryProducer: (() -> ViewModelProvider.Factory)? = null
): Lazy<VM> {
    val factoryPromise = factoryProducer ?: {
        val application = application ?: throw IllegalArgumentException(
                "ViewModel can be accessed only when Activity is attached"
        )
        ViewModelProvider.AndroidViewModelFactory.getInstance(application)
    }

    return ViewModelLazy(VM::class, { viewModelStore }, factoryPromise)
}

score 1 · Answer 11 · answered Dec 27 '20 at 11:26

1

Try this one. It works for me.

implementation "androidx.fragment:fragment-ktx:1.2.5"

answered Dec 27 '20 at 11:26

Apps Developer

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score 1 · Answer 12 · edited Dec 30 '21 at 19:00

1

You can fix it by implementing the fragment-ktx library like this

def fragment_version = "1.4.0"

implementation("androidx.fragment:fragment-ktx:$fragment_version")

See more and check latest version here.

edited Dec 30 '21 at 19:00

answered Dec 30 '21 at 18:39

Abdulsalam Al-Hammadi

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Blundell · Answer 13 · 2020-05-08T19:35:55.690

-5

If you have come here looking for a solution for Koin:

Note you can use use Koin to make this work:

private val viewModel by viewModel<NoteViewModel>()

would use the import

import org.koin.android.viewmodel.ext.android.viewModel

from the dependency:

implementation "org.koin:koin-android-viewmodel:+" // change + to w/e is the latest when u read this

edited May 08 '20 at 19:35

answered Dec 16 '19 at 16:53

Blundell

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(answer cos I was looking myself, and google sent me here!) – Blundell Dec 16 '19 at 16:54
yes, it's very tricky to have the right imports when using `koin` but this question is not related to koin. – Anmol Dec 17 '19 at 06:37
The question came up on Google when searching for Koin problems, (same symptoms) so you never know :) – Blundell Dec 17 '19 at 12:06
Why is Koin necessary? – IgorGanapolsky Jan 17 '20 at 00:53
Koin has the same api. So it's not necessary, its an alternative with the same problem. – Blundell Jan 17 '20 at 08:52
I just think you would get better acknowledge of your answer if you explain why you're suggesting coin in the answer itself instead of comments. – Machado May 07 '20 at 14:04

how to get viewModel by viewModels? (fragment-ktx)

13 Answers13

Compiler Error:

`build.gradle` (Module `:app`)

2021 UPDATE

UPDATE 2022 APRIL 29

Linked

how to get viewModel by viewModels? (fragment-ktx)

13 Answers13

Compiler Error:

build.gradle (Module :app)

2021 UPDATE

UPDATE 2022 APRIL 29

Linked

`build.gradle` (Module `:app`)