android - 使用匕首 2 注入视图模型依赖项

Question

我在将依赖项注入我的 viewModel 时遇到问题。我不断收到无法创建类 ....viewModel.UserProfileViewModel 的实例。我一直在试图弄清楚这个问题。任何建议将不胜感激。这是我的代码。我在其他问题中看到，这通常是由于在视图模型的构造函数中有一个参数，创建一个工厂应该可以解决这个问题。但这对我来说似乎效果不佳。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：致命异常：主进程：nonso.android.nonso，PID：19211 java.lang.RuntimeException：无法创建类 nonso.android 的实例.nonso.viewModel.UserProfileViewModel 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android 上的 nonso.android.nonso.ui.fragments.ProfileFragment.onActivityCreated(ProfileFragment.java:122)。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.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(Native Method) 在 com.android .internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 原因：java.lang.InstantiationException: java.lang.Class在 android.arch.lifecycle 的 android.arch.lifecycle.ViewModelProvider$NewInstanceFactory.create(ViewModelProvider.java:151) 的 java.lang.Class.newInstance(Native Method) 没有零参数构造函数。ViewModelProvider$AndroidViewModelFactory.create(ViewModelProvider.java:210) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134) at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102) at 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.execPendingActions(FragmentManager.java:2245) 在 android.support.v4.app.FragmentManagerImpl $1.run(FragmentManager.java:703) 在 android.os.Handler.handleCallback(Handler.java:790) 在 android.os.Handler.dispatchMessage(Handler.java:99) 在 android.os.Looper.loop(Looper .java:164) 在 android.app.ActivityThread.main(ActivityThread.java:6494) 在 java.lang.reflect.Method。在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 的 com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 调用（本机方法）