Jetpack Compose + Hilt：java.lang.RuntimeException：无法创建 class ViewModel 的实例

Question

我最近开始尝试使用 jetpack Compose，并为我的应用程序使用了 hilt 和 hilt-navigation-compose。它适用于第一个 ViewModel。但是，当我在第二个屏幕的另一个 ViewModel 上尝试相同的代码时，它总是崩溃并显示 java.lang.RuntimeException：无法创建 class 的实例。但是如果我在它的构造函数中去掉参数repository(Injected using Hilt)，就可以初始化成功了。

目前在我的导航图中有四个screens.HOME，RECORD，SETTING screen可以通过BottomBar导航到，它们的viewModel可以正常工作；NEW screen可以通过FloatingActionButton导航到，但是它的viewModel不能像其他人一样创造。我无法弄清楚问题所在。这是我的后台跟踪：

java.lang.RuntimeException: Cannot create an instance of class com.eynnzerr.cpbookkeeping_compose.ui.new.NewViewModel
...
Caused by: java.lang.InstantiationException: java.lang.Class<com.eynnzerr.cpbookkeeping_compose.ui.new.NewViewModel> has no zero argument constructor

似乎 Hilt 只知道如何使用无参数构造函数创建 NewViewModel 而忽略了它的参数库？

这是我的代码： (1)Hilt应用class:

    @HiltAndroidApp
    class CPApplication: Application() {
        override fun onCreate() {
            super.onCreate()
            context = applicationContext
        }

        companion object {
            @SuppressLint("StaticFieldLeak")
            lateinit var context: Context
        }
    }

(2)主要活动：

@AndroidEntryPoint
class MainActivity : ComponentActivity() {
    @RequiresApi(Build.VERSION_CODES.N)
    @ExperimentalAnimationApi
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            BookkeepingApp()         
        }
    }
}

@ExperimentalAnimationApi
@Composable
fun BookkeepingApp() {
    CPBookkeepingcomposeTheme {
        val navController = rememberNavController()
        BasicScreen(
            navController = navController
        )
    }
}

@ExperimentalAnimationApi
@Composable
fun BasicScreen(
    navController: NavController
) {
    ...
    Scaffold(
        topBar = {
            //Change according to currentScreen in composable.
            CPTopBar(currentScreen)
        },
        floatingActionButton = {
            //only show up when it's HOME screen.
            if(currentScreen.value == Destinations.HOME_ROUTE) {
                DraggableFloatingButton(
                    onClick = {
                        navController.navigateTo(Destinations.NEW_ROUTE)
                    }
                )
            } else Unit
        },
        bottomBar = {
            //only show up when it's HOME, RECORD, SETTING screens.
            AnimatedVisibility(listState.isScrollingUp()) {
                when(currentScreen.value) {
                    Destinations.HOME_ROUTE,
                    Destinations.RECORD_ROUTE,
                    Destinations.SETTING_ROUTE -> FlutterNavigation(navController = navController, items)
                    else -> Unit
                }
            }
        }
    ) {
        NavGraph(
            navController = navController as NavHostController,
            listState = listState
        )
    }
}

(3)导航图：

@Composable
fun NavGraph(
    navController: NavHostController = rememberNavController(),
    listState: LazyListState = rememberLazyListState(),
    startDestination: String = Destinations.HOME_ROUTE
) {
    NavHost(navController = navController, startDestination = "home") {
        composable(Destinations.HOME_ROUTE){
            //can create ViewModel.
            val homeViewModel: HomeViewModel = hiltViewModel()
            ...
        }
        ...
        composable(Destinations.NEW_ROUTE){
            //cannot create ViewModel?
            val newViewModel: NewViewModel = hiltViewModel()
            ...
        }
    }
}

(4)HomeViewModel（效果很好）：

data class HomeUiState(
    val billsToday: List<Bill> = emptyList(),
    val homeData: HomeData = HomeData()
)

@HiltViewModel
class HomeViewModel @Inject constructor(
    private val billRepository: BillRepositoryImpl
): ViewModel() {
    private val _uiState = MutableStateFlow(HomeUiState())
    val uiState: StateFlow<HomeUiState> = _uiState 

    init {
        viewModelScope.launch {
            _uiState.update { it.copy(homeData = getAllData(0f)) }
            billRepository.getBillsFlow().collect { bills ->
                _uiState.update { it.copy(billsToday = bills) }
            }
        }
    }
}

(5)NewViewModel(除了删除billRepository无法创建):

data class TabState(
    val amount: String = "¥0",
    val selectedIndex: Int = 0
)

@HiltViewModel
class NewViewModel @Inject constructor(
    private val billRepository: BillRepositoryImpl //After deleting this, it can work properly
) : ViewModel() {

    //uiState for expenseTab
    private val _exTabState = MutableStateFlow(TabState())
    val exTabState: StateFlow<TabState> = _exTabState.asStateFlow()

    //uiState for revenueTab
    private val _reTabState = MutableStateFlow(TabState())
    val reTabState: StateFlow<TabState> = _reTabState.asStateFlow()

    private val _remarkState = MutableStateFlow("add remark")
    val remarkState: StateFlow<String> = _remarkState.asStateFlow()

    fun updateRemark(remark: String) {
        _remarkState.update { remark }
    }

    fun updateTab(category: Int, amount: String, selectedIndex: Int) {
        when(category) {
            -1 -> _exTabState.update { it.copy(amount = amount, selectedIndex = selectedIndex) }
            1 -> _reTabState.update { it.copy(amount = amount, selectedIndex = selectedIndex) }
        }
    }

    fun insertBill(bill: Bill) {
        viewModelScope.launch {
            billRepository.insertBills(bill)
        }
    }
}

(6)billRepository:

class BillRepositoryImpl @Inject constructor() : BillRepository {
    private val billDao = BillDatabase.getInstance(context).getDao()

    override suspend fun getBillsFlow(): Flow<List<Bill>> = billDao.getAllBills()

    override suspend fun insertBills(vararg bill: Bill) = billDao.insertBills(*bill)

    override suspend fun deleteBills(vararg bill: Bill) = billDao.deleteBills(*bill)

    override suspend fun updateBills(vararg bill: Bill) = billDao.updateBills(*bill)
}

interface BillRepository {

    suspend fun getBillsFlow(): Flow<List<Bill>>

    suspend fun insertBills(vararg bill: Bill)

    suspend fun deleteBills(vararg bill: Bill)

    suspend fun updateBills(vararg bill: Bill)
}

(7)build.gradle(项目):

buildscript {
    ext {
        compose_version = '1.1.0-beta02'
        hilt_version = "2.37"
        work_version = "2.7.1"
        datastore_version = "1.0.0"
    }
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:7.0.4'
        classpath 'org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.31'

        classpath "com.google.dagger:hilt-android-gradle-plugin:$hilt_version"
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

(8)build.gradle(应用程序):

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

apply plugin: 'kotlin-kapt'//hilt support
apply plugin: 'dagger.hilt.android.plugin'//hilt support

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.eynnzerr.cpbookkeeping_compose"
        minSdk 21
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        vectorDrawables {
            useSupportLibrary true
        }

        javaCompileOptions {
            annotationProcessorOptions {
                arguments += [
                        "room.schemaLocation":"$projectDir/schemas".toString(),
                        "room.incremental":"true",
                        "room.expandProjection":"true"]
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
        useIR = true
    }
    buildFeatures {
        compose true
    }
    composeOptions {
        kotlinCompilerExtensionVersion compose_version
        kotlinCompilerVersion '1.5.31'
    }
    packagingOptions {
        resources {
            excludes += '/META-INF/{AL2.0,LGPL2.1}'
        }
    }
}

dependencies {

    implementation "io.github.vanpra.compose-material-dialogs:datetime:0.6.2"

    implementation "androidx.datastore:datastore-preferences:$datastore_version"
    implementation "androidx.datastore:datastore:$datastore_version"
    implementation "androidx.work:work-runtime-ktx:$work_version"

    def room_version = "2.4.0-beta02"
    implementation "androidx.room:room-runtime:$room_version"
    implementation "androidx.room:room-ktx:$room_version"
    kapt "androidx.room:room-compiler:$room_version"

    implementation "com.google.dagger:hilt-android:$hilt_version"
    kapt "com.google.dagger:hilt-android-compiler:$hilt_version"

    implementation "androidx.hilt:hilt-navigation-compose:1.0.0-beta01"
    implementation "androidx.navigation:navigation-compose:2.4.0-beta02"

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.3.0'
    implementation "androidx.compose.ui:ui:$compose_version"
    implementation "androidx.compose.foundation:foundation:$compose_version"
    implementation "androidx.compose.material:material:$compose_version"
    implementation "androidx.compose.material:material-icons-core:$compose_version"
    implementation "androidx.compose.material:material-icons-extended:$compose_version"
    implementation "androidx.compose.ui:ui-tooling-preview:$compose_version"
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
    implementation 'androidx.activity:activity-compose:1.4.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    androidTestImplementation "androidx.compose.ui:ui-test-junit4:$compose_version"
    debugImplementation "androidx.compose.ui:ui-tooling:$compose_version"
}

Answer 1

提出这个问题后我得到了答案... 似乎你不能用“新”来命名包，我在我的应用程序中这样做了： com.eynnzerr.cpbookkeeping_compose.ui.new.NewViewModel 因为它是保留的，你甚至不能用它来命名你的包...编辑后我的问题就解决了...

Answer 2

我刚刚遇到了类似的问题，幸运的是我找到了这个主题。在我的例子中，我将命名空间命名为“messages”并重命名该命名空间有效

Jetpack Compose + Hilt：java.lang.RuntimeException：无法创建 class ViewModel 的实例

Jetpack Compose + Hilt: java.lang.RuntimeException: Cannot create an instance of class ViewModel

android

kotlin

android-jetpack-compose

dagger-hilt

android-jetpack-navigation