我正在尝试使用匕首刀柄来提供我的片段视图模型。 所以我像这样注释了我的视图模型：
@HiltViewModel
class MainViewModel @Inject constructor(private val database: TasksDatabase) : ViewModel() {
...
}
此外，我还用 @AndroidEntryPoint 注释了我的活动和片段
然后在我的片段中，我像这样实例化了我的 ViewModel：
private val viewModel: MainViewModel by viewModels()
另外，因为 ViewModel 需要一个数据库所以我创建了一个 Hilt 模块：
@Module
@InstallIn(SingletonComponent::class)
object AppModule {
@Singleton
@Provides
fun provideDatabase(@ApplicationContext context: Context) = Room.databaseBuilder(
context.applicationContext,
TasksDatabase::class.java,
"student_database"
).fallbackToDestructiveMigration().build()
}
应用程序将编译但崩溃：
androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment done.main.MainFragment: calling Fragment constructor caused an exception
at androidx.fragment.app.Fragment.instantiate(Fragment.java:631)
at androidx.navigation.fragment.FragmentNavigator.instantiateFragment(FragmentNavigator.java:184)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:212)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:58)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:80)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:30)
at androidx.navigation.NavController.navigate(NavController.java:823)
at androidx.navigation.NavController.onGraphCreated(NavController.java:521)
at androidx.navigation.NavController.setGraph(NavController.java:482)
at androidx.navigation.NavController.setGraph(NavController.java:447)
at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:235)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:305)
at done.NavigationExtensionsKt.obtainNavHostFragment(NavigationExtensions.kt:225)
at done.NavigationExtensionsKt.setupWithNavController(NavigationExtensions.kt:34)
at done.MainActivity.setNavigation(MainActivity.kt:49)
at done.MainActivity.onCreate(MainActivity.kt:23)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:430)
at androidx.fragment.app.Fragment.instantiate(Fragment.java:613)
at androidx.navigation.fragment.FragmentNavigator.instantiateFragment(FragmentNavigator.java:184)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:212)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:58)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:80)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:30)
at androidx.navigation.NavController.navigate(NavController.java:823)
at androidx.navigation.NavController.onGraphCreated(NavController.java:521)
at androidx.navigation.NavController.setGraph(NavController.java:482)
at androidx.navigation.NavController.setGraph(NavController.java:447)
at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:235)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:305)
at done.NavigationExtensionsKt.obtainNavHostFragment(NavigationExtensions.kt:225)
at done.NavigationExtensionsKt.setupWithNavController(NavigationExtensions.kt:34)
at done.MainActivity.setNavigation(MainActivity.kt:49)
at done.MainActivity.onCreate(MainActivity.kt:23)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.IllegalStateException: Fragment MainFragment{c9d8770} (76068e8e-d2f9-481b-8c21-2221e637565b) not attached to a context.
at androidx.fragment.app.Fragment.requireContext(Fragment.java:900)
at done.main.MainFragment.<init>(MainFragment.kt:57)
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:430)
at androidx.fragment.app.Fragment.instantiate(Fragment.java:613)
at androidx.navigation.fragment.FragmentNavigator.instantiateFragment(FragmentNavigator.java:184)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:212)
at androidx.navigation.fragment.FragmentNavigator.navigate(FragmentNavigator.java:58)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:80)
at androidx.navigation.NavGraphNavigator.navigate(NavGraphNavigator.java:30)
at androidx.navigation.NavController.navigate(NavController.java:823)
at androidx.navigation.NavController.onGraphCreated(NavController.java:521)
at androidx.navigation.NavController.setGraph(NavController.java:482)
at androidx.navigation.NavController.setGraph(NavController.java:447)
at androidx.navigation.fragment.NavHostFragment.onCreate(NavHostFragment.java:235)
at androidx.fragment.app.Fragment.performCreate(Fragment.java:2949)
at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:475)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:278)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2189)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:2100)
at androidx.fragment.app.FragmentManager.execSingleAction(FragmentManager.java:1971)
at androidx.fragment.app.BackStackRecord.commitNow(BackStackRecord.java:305)
at done.NavigationExtensionsKt.obtainNavHostFragment(NavigationExtensions.kt:225)
at done.NavigationExtensionsKt.setupWithNavController(NavigationExtensions.kt:34)
at done.MainActivity.setNavigation(MainActivity.kt:49)
at done.MainActivity.onCreate(MainActivity.kt:23)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
更新： 我使用导航组件来管理 MainActivity 中的片段：
@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
if (savedInstanceState == null)
setNavigation()
}
override fun onRestoreInstanceState(savedInstanceState: Bundle) {
super.onRestoreInstanceState(savedInstanceState)
setNavigation()
}
private fun setNavigation() {
val graphID = listOf(
R.navigation.home,
R.navigation.profile,
R.navigation.tasks
)
binding.bottomMenu.setupWithNavController(
navGraphIds = graphID,
fragmentManager = supportFragmentManager,
containerId = binding.container.id, intent = intent
)
}
}
导航扩展是this link
我想知道应用运行良好，直到我提供了 Hilt 的 ViewModel，那么我如何使用 hilt 提供我的 ViewModel？