Question

在将依赖项注入到viewModel中时遇到问题。我不断收到无法创建类.... viewModel.UserProfileViewModel的实例。我一直试图找出这个问题。任何建议将不胜感激。这是我的代码。在其他问题中，我看到这通常是由于在viewmodel的构造函数中有一个参数引起的，创建工厂可以解决该问题。但是对于我来说，效果似乎不太好。我肯定错过了什么。

谢谢！

 App component:

@Singleton
@Component(modules = {AndroidSupportInjectionModule.class, ViewModelModule.class})
public interface ApplicationComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance Builder application(Application application);
        ApplicationComponent build();
    }
}
=====================================================
App module:

@Module
public class AppModule {
    Application mApplication;


    public AppModule(Application application){
        mApplication = application;
    }


    @Provides
    @Singleton
    Application providesApplication(){
        return mApplication;
    }
}

===========================================================
ViewFactory

@Singleton
public class ViewModelFactory implements ViewModelProvider.Factory {

    private final Map<Class<? extends ViewModel>, Provider<ViewModel>> creators;

    @Inject
    public ViewModelFactory(Map<Class<? extends ViewModel>, Provider<ViewModel>> viewModels) {
        this.creators = viewModels;
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
        Provider<? extends ViewModel> creator = creators.get(modelClass);

        if (creator == null) {
            for (Map.Entry<Class<? extends ViewModel>, Provider<ViewModel>> entry : creators.entrySet()) {
                if (modelClass.isAssignableFrom(entry.getKey())) {
                    creator = entry.getValue();
                    break;
                }
            }
        }
        if (creator == null) {
            throw new IllegalArgumentException("unknown model class " + modelClass);
        }
        try {
            return (T) creator.get();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

===========================================================
View key

@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@MapKey
@interface ViewModelKey {
    Class<? extends ViewModel> value();
}

========================================================
View Module

@Module
public abstract class ViewModelModule {

    @Binds
    @IntoMap
    @ViewModelKey(UserProfileViewModel.class)
    abstract ViewModel bindUserViewModel(UserProfileViewModel userViewModel);
}

===========================================================
view model class

public class UserProfileViewModel extends ViewModel {

    private UserRepository mUserRepository;
    private LiveData<User> mObservableUser;

    @Inject
    public UserProfileViewModel(@NonNull UserRepository userRepo){
        this.mUserRepository = userRepo;
    }


    public void init(String userId){
        if (this.mObservableUser != null) {
            return;
        }
        mObservableUser = mUserRepository.getUser(userId);
    }

    public LiveData<User> getUser() {
        return this.mObservableUser;
    }

}

 ====================================================
in fragment

 viewModel = ViewModelProviders.of(this, viewModelFactory).get(UserProfileViewModel.class);
        viewModel.init(mUserId);

堆栈跟踪22：08：49.677 19211-19211 / nonso.android.nonso E / AndroidRuntime：FATAL EXCEPTION：main 进程：nonso.android.nonso，PID：19211 java.lang.RuntimeException：无法创建类nonso.android.nonso.viewModel.UserProfileViewModel的实例在android.arch.lifecycle.ViewModelProvider $ NewInstanceFactory.create（ViewModelProvider.java:153）在android.arch.lifecycle.ViewModelProvider $ AndroidViewModelFactory.create（ViewModelProvider.java:210）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:134）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:102）在nonso.android.nonso.ui.fragments.ProfileFragment.setUp（ProfileFragment.java:133）在nonso.android.nonso.ui.fragments.ProfileFragment.onActivityCreated（ProfileFragment.java:122）在android.support.v4.app.Fragment.performActivityCreated（Fragment.java:2355）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1451）在android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState（FragmentManager.java:1759）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1827）在android.support.v4.app.BackStackRecord.executeOps（BackStackRecord.java:797）在android.support.v4.app.FragmentManagerImpl.executeOps（FragmentManager.java:2596）在android.support.v4.app.FragmentManagerImpl.executeOpsTogether（FragmentManager.java:2383）在android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute（FragmentManager.java:2338）在android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:2245）在android.support.v4.app.FragmentManagerImpl $ 1.run（FragmentManager.java:703）在android.os.Handler.handleCallback（Handler.java:790）在android.os.Handler.dispatchMessage（Handler.java:99）在android.os.Looper.loop（Looper.java:164）在android.app.ActivityThread.main（ActivityThread.java:6494）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:438）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:807）原因：java.lang.InstantiationException：java.lang.Class没有零参数构造函数在java.lang.Class.newInstance（本地方法）在android.arch.lifecycle.ViewModelProvider $ NewInstanceFactory.create（ViewModelProvider.java:151）在android.arch.lifecycle.ViewModelProvider $ AndroidViewModelFactory.create（ViewModelProvider.java:210）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:134）在android.arch.lifecycle.ViewModelProvider.get（ViewModelProvider.java:102）在nonso.android.nonso.ui.fragments.ProfileFragment.setUp（ProfileFragment.java:133）在nonso.android.nonso.ui.fragments.ProfileFragment.onActivityCreated（ProfileFragment.java:122）在android.support.v4.app.Fragment.performActivityCreated（Fragment.java:2355）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1451）在android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState（FragmentManager.java:1759）在android.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager.java:1827）在android.support.v4.app.BackStackRecord.executeOps（BackStackRecord.java:797）在android.support.v4.app.FragmentManagerImpl.executeOps（FragmentManager.java:2596）在android.support.v4.app.FragmentManagerImpl.executeOpsTogether（FragmentManager.java:2383）在android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute（FragmentManager.java:2338）在android.support.v4.app.FragmentManagerImpl.execPendingActions（FragmentManager.java:2245）在android.support.v4.app.FragmentManagerImpl $ 1.run（FragmentManager.java:703）在android.os.Handler.handleCallback（Handler.java:790）在android.os.Handler.dispatchMessage（Handler.java:99）在android.os.Looper.loop（Looper.java:164）在android.app.ActivityThread.main（ActivityThread.java:6494）在java.lang.reflect.Method.invoke（本机方法）在com.android.internal.os.RuntimeInit $ MethodAndArgsCaller.run（RuntimeInit.java:438） com.android.internal.os.ZygoteInit.main（ZygoteInit.java:807）

使用匕首2注入viewmodel依赖项

0 个答案: