jetpack compose viewModel() 给出错误“没有零参数构造函数”，带有刀柄

Question

In my project, compose viewModel() method is giving error "has no zero argument constructor" when I am using hilt.

@Composable
    fun HomeScreen(homeViewModel: HomeViewModel = viewModel()) {
    ...
    }
    
    @HiltViewModel
    class HomeViewModel @Inject constructor(private val repository: Repository) :
        ViewModel() {
    ...
    }
@Module
@InstallIn(ViewModelComponent::class)
abstract class DataModule {
    @Binds
    abstract fun bindRepository(
        fakePuppyRepository: RepositoryImpl
    ): Repository
}

these are my dependencies

implementation 'androidx.core:core-ktx:1.3.2'
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation "androidx.compose.ui:ui:$compose_version"
    implementation "androidx.compose.material:material:$compose_version"
    implementation "androidx.compose.ui:ui-tooling:$compose_version"
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.0'
    implementation 'androidx.activity:activity-compose:1.3.0-alpha03'
    implementation "androidx.navigation:navigation-compose:1.0.0-alpha08"
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.3.0'
    implementation 'androidx.compose.runtime:runtime-livedata:1.0.0-beta01'
    implementation "com.google.dagger:hilt-android:$hilt_version"
    implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha03'
    kapt "com.google.dagger:hilt-compiler:$hilt_version"
    kapt 'androidx.hilt:hilt-compiler:1.0.0-alpha03'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'

Answer 1

Based on your dependencies, I suspect you are using NavController/NavHost.

Add this dependency: androidx.hilt:hilt-navigation-compose:1.0.0-alpha01

Now in your composable which defines NavController, call HomeScreen as follows:

import androidx.compose.runtime.Composable
import androidx.hilt.navigation.compose.hiltNavGraphViewModel
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
import androidx.navigation.compose.rememberNavController

...

@Composable
fun Main() {
  val navController = rememberNavController()
  NavHost(navController, startDestination = "home"){
    composable("home") {
      val model: HomeViewModel = hiltNavGraphViewModel(it)
      HomeScreen(model)
    }
  }
}

...

hiltNavGraphViewModel(...) can also be replaced with viewModel(HiltViewModelFactory(LocalContext.current, backStackEntry)) (from https://github.com/google/dagger/issues/2166#issuecomment-769162910 )

Answer 2

The hiltNavGraphViewModel() extension has been deprecated. You can use hiltViewModel() instead if you use Navigation and Hilt.

First, add this dependency:

implementation 'androidx.hilt:hilt-navigation-compose:1.0.0-alpha03'

And now you can use hiltViewModel() together with Navigation.

@Composable
fun MyApp() {
    NavHost(navController, startDestination = startRoute) {
        composable("example") { backStackEntry ->
            // Creates a ViewModel from the current BackStackEntry
            // Available in the androidx.hilt:hilt-navigation-compose artifact
            val exampleViewModel = hiltViewModel<ExampleViewModel>()
            ExampleScreen(exampleViewModel)
        }
        /* ... */
    }
}

More information: Hilt and Navigation

Answer 3

Happened to me when I set my ViewModel inside a package called new .

Let's say my base package is com.example.appname , I created a new pakage called new and I had com.example.appname.new , every other ViewModel factories were created successfully by Hilt with the exception the one inside of package new .

1. Rename the package with name new , it looks like it is reserved.
2. Move your ViewModel to another location.

Answer 4

Make sure your Activity/Fragments which enclose the composables have @AndroidEntryPoint and you have the latest version of hilt dependencies.