android–ViewModelProviders with Dagger 2,无法掌握这个概念

概述我有这样的改造服务publicinterfaceBrandsService{@GET("listBrand")Call<List<Brand>>getBrands();}然后我有一个Repository来从这样的api获取数据publicclassBrandsRepository{publicstaticfinalStringTAG="BrandsRepository";

我有这样的改造服务

public interface BrandsService {    @GET("ListBrand")    Call<List<Brand>> getBrands();}

然后我有一个Repository来从这样的API获取数据

public class BrandsRepository {    public static final String TAG = "BrandsRepository";    mutablelivedata<List<Brand>> mutablelivedata;    Retrofit retrofit;    @Inject    public BrandsRepository(Retrofit retrofit) {        this.retrofit = retrofit;    }    public liveData<List<Brand>> getlistofBrands() {//       Retrofit retrofit = apimanager.getAdapter();        final BrandsService brandsService = retrofit.create(BrandsService.class);        Log.d(TAG, "getlistofBrands: 00000000000 "+retrofit);        mutablelivedata = new mutablelivedata<>();        Call<List<Brand>> retrofitCall = brandsService.getBrands();        retrofitCall.enqueue(new Callback<List<Brand>>() {            @OverrIDe            public voID onResponse(Call<List<Brand>> call, Response<List<Brand>> response) {                mutablelivedata.setValue(response.body());            }            @OverrIDe            public voID onFailure(Call<List<Brand>> call, Throwable t) {                t.printstacktrace();            }        });        return mutablelivedata;    }}

我通过像这样注入Retrofit来使用Dagger2的构造函数注入.
然后我有一个像这样的viewmodel

public class Brandsviewmodel extends viewmodel{    BrandsRepository brandsRepository;    liveData<List<Brand>> brandsliveData;    @Inject    public Brandsviewmodel(BrandsRepository brandsRepository) {        this.brandsRepository = brandsRepository;    }    public voID callService(){       brandsliveData = brandsRepository.getlistofBrands();    }    public liveData<List<Brand>> getBrandsliveData() {        return brandsliveData;    }}

要在BrandsRepository中注入Retrofit,我必须像这样注入BrandsRepository.
然后我有这样的MainActivity

public class MainActivity extends AppCompatActivity {    private static final String TAG = "MainActivity";    @Inject    Brandsviewmodel brandsviewmodel;    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);        ((MainApplication)getApplication()).getNetComponent().inject(this);//        Brandsviewmodel brandsviewmodel = viewmodelProvIDers.of(this).get(Brandsviewmodel.class);        brandsviewmodel.callService();        liveData<List<Brand>> brandsliveData = brandsviewmodel.getBrandsliveData();        brandsliveData.observe(this, new Observer<List<Brand>>() {            @OverrIDe            public voID onChanged(@Nullable List<Brand> brands) {                Log.d(TAG, "onCreate: "+brands.get(0).getname());            }        });    }}

使用Dagger2而不是viewmodelProvIDers注入Brandsviewmodel.这工作正常,但当我尝试通过取消注释使用viewmodelProvIDers时,dagger给了我很明显的错误.获取viewmodel的正确方法是使用viewmodelProvIDers,但是如何在注入这样的改进时完成此 *** 作.

解决方法:

答案可能比Mumi的方法更简单,即您在组件上公开viewmodel：

@Singleton@Component(modules={...})public interface SingletonComponent {    Brandsviewmodel brandsviewmodel();}

现在,您可以在viewmodelFactory中的组件上访问此方法：

// @InjectBrandsviewmodel brandsviewmodel;...brandsviewmodel = viewmodelProvIDers.of(this, new viewmodelProvIDer.Factory() {    @OverrIDe    public <T extends viewmodel> create(Class<T> modelClazz) {        if(modelClazz == Brandsviewmodel.class) {            return singletonComponent.brandsviewmodel();        }        throw new IllegalArgumentException("Unexpected class: [" + modelClazz + "]");    }).get(Brandsviewmodel.class);

所有这些都可以通过Kotlin简化和隐藏：

inline fun <reifIEd T: viewmodel> AppCompatActivity.createviewmodel(crossinline factory: () -> T): T = T::class.java.let { clazz ->    viewmodelProvIDers.of(this, object: viewmodelProvIDer.Factory {        overrIDe fun <T : viewmodel?> create(modelClass: Class<T>): T {            if(modelClass == clazz) {                @Suppress("UNCHECKED_CAST")                return factory() as T            }            throw IllegalArgumentException("Unexpected argument: $modelClass")        }    }).get(clazz)}

现在可以让你做到

brandsviewmodel = createviewmodel { singletonComponent.brandsviewmodel() }

现在Brandsviewmodel可以从Dagger接收其参数：

class Brandsviewmodel @Inject constructor(    private val appContext: Context,    /* other deps */): viewmodel() {    ...}

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