viewmodel在java中没有零参数构造函数

vqlkdk9b  于 2021-07-03  发布在  Java
关注(0)|答案(1)|浏览(452)

我正在使用 hilt 我想把我的进口 SessionManager 进入我的 AuthViewModel 班级。
当我们用viewmodel查看google的文档时，我们可以看到他们能够注入 ExampleRepository repository 进入赛义德的建造师 ExampleViewModel ```
public class ExampleViewModel extends ViewModel {

private final ExampleRepository repository;
private final SavedStateHandle savedStateHandle;

@ViewModelInject
ExampleViewModel(
ExampleRepository repository,
@Assisted SavedStateHandle savedStateHandle)
{
this.repository = repository;
this.savedStateHandle = savedStateHandle;
}
...
}

和

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
exampleViewModel = new ViewModelProvider(this).get(ExampleViewModel.class);
}

每当我试图这样做，我的项目不断得到的错误。

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.atchat.donation, PID: 11005
java.lang.RuntimeException: Cannot create an instance of class com.atchat.donation.ui.auth.AuthViewModel
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:221)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:278)
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106)
at androidx.hilt.lifecycle.HiltViewModelFactory.create(HiltViewModelFactory.java:74)
at androidx.lifecycle.AbstractSavedStateViewModelFactory.create(AbstractSavedStateViewModelFactory.java:69)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185)
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150)
at com.atchat.donation.ui.auth.LoginFragment.onViewCreated(LoginFragment.java:97)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:332)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1199)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2236)
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2009)
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1965)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1861)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2641)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2589)
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2723)
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1200)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1368)
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1446)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1509)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2637)
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2589)
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:247)
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:541)
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:210)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425)
at android.app.Activity.performStart(Activity.java:7825)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201)
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.InstantiationException: java.lang.Class<com.atchat.donation.ui.auth.AuthViewModel> has no zero argument constructor
at java.lang.Class.newInstance(Native Method)
at androidx.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:219)
at androidx.lifecycle.ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:278) 
at androidx.lifecycle.SavedStateViewModelFactory.create(SavedStateViewModelFactory.java:106) 
at androidx.hilt.lifecycle.HiltViewModelFactory.create(HiltViewModelFactory.java:74) 
at androidx.lifecycle.AbstractSavedStateViewModelFactory.create(AbstractSavedStateViewModelFactory.java:69) 
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:185) 
at androidx.lifecycle.ViewModelProvider.get(ViewModelProvider.java:150) 
at com.atchat.donation.ui.auth.LoginFragment.onViewCreated(LoginFragment.java:97) 
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:332) 
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1199) 
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2236) 
at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:2009) 
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1965) 
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1861) 
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2641) 
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2589) 
at androidx.fragment.app.Fragment.performActivityCreated(Fragment.java:2723) 
at androidx.fragment.app.FragmentStateManager.activityCreated(FragmentStateManager.java:346) 
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1200) 
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1368) 
at androidx.fragment.app.FragmentManager.moveFragmentToExpectedState(FragmentManager.java:1446) 
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1509) 
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2637) 
at androidx.fragment.app.FragmentManager.dispatchActivityCreated(FragmentManager.java:2589) 
at androidx.fragment.app.FragmentController.dispatchActivityCreated(FragmentController.java:247) 
at androidx.fragment.app.FragmentActivity.onStart(FragmentActivity.java:541) 
at androidx.appcompat.app.AppCompatActivity.onStart(AppCompatActivity.java:210) 
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1425) 
at android.app.Activity.performStart(Activity.java:7825) 
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:3294) 
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:221) 
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:201) 
at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:173) 
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
at android.os.Handler.dispatchMessage(Handler.java:107) 
at android.os.Looper.loop(Looper.java:214) 
at android.app.ActivityThread.main(ActivityThread.java:7356) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930) 
I/Process: Sending signal. PID: 11005 SIG: 9

AuthView模型

public class AuthViewModel extends ViewModel {

private static final String TAG = "AuthViewModel";
private final SessionManager sessionManager;

@ViewModelInject
public AuthViewModel(SessionManager sessionManager, @Assisted SavedStateHandle savedStateHandle){
    this.sessionManager = sessionManager;
}

...
}

应用程序模块

@Module()
@InstallIn(SingletonComponent.class)
public class AppModule {

@Provides
public static SessionManager provideSessionManager(@ApplicationContext Context context, AccountRestService accountRestService){
    return new SessionManager(accountRestService, context);
}

...
}

登录碎片

@AndroidEntryPoint
public class LoginFragment extends Fragment implements View.OnClickListener {

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    viewModel = new ViewModelProvider(this).get(AuthViewModel.class);
    subscribeObservers();
    attemptSilentLogin();
}

...
}

build.gradle（模块）

apply plugin: 'dagger.hilt.android.plugin'

dependencies {

//Hilt
implementation 'com.google.dagger:hilt-android:2.30-alpha'
implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha02'
annotationProcessor 'com.google.dagger:hilt-android-compiler:2.30-alpha'

...
}

build.gradle（项目）

dependencies {
classpath 'com.android.tools.build:gradle:4.1.1'
classpath 'com.google.dagger:hilt-android-gradle-plugin:2.30-alpha'
}

Javaandroidviewmodeldagger-hiltandroid-lifecycle

1条答案

按热度按时间
ne5o7dgx

ne5o7dgx1#

您的错误消息显示 HiltViewModelFactory 没有为您的特定 AuthViewModel . 没有，因为你没有包括额外的 annotationProcessor 这是需要专门为刀柄和喷气背包集成-这是额外的 androidx.hilt:hilt-compiler 负责读取 @ViewModelInject 并生成正确的刀柄绑定。

dependencies {
    // Hilt
    implementation 'com.google.dagger:hilt-android:2.30-alpha'
    annotationProcessor 'com.google.dagger:hilt-android-compiler:2.30-alpha'

    // Hilt Jetpack Integrations
    implementation 'androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha02'
    annotationProcessor 'androidx.hilt:hilt-compiler:1.0.0-alpha02'
...
}
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