如何使用 dagger-android 与演示者相互 link 片段？

Question

我想要一个提供视图（片段）和演示者的片段模块。 View 依赖于 presenter，presenter 依赖于 view，而 dagger 负责处理这些依赖关系。

我见过这种方法适用于活动和演示者，但未能将这种模式应用于片段。我想知道这是由于我的代码错误，还是 dagger 的限制。

这是我用于活动的基准代码：

主要Activity合同

public interface MainActivityContract {
    interface View {
        void setText(String text);
    }

    interface Presenter {
        void attach();
    }
}

主要Activity模块

@Module
public abstract class MainActivityModule {

    @Binds
    abstract MainActivityContract.View exampleFragment(MainActivity view);

    @Binds
    abstract MainActivityContract.Presenter exampleFragmentPresenter(MainActivityPresenter presenter);
}

Activity代码:

public class MainActivity extends DaggerAppCompatActivity implements MainActivityContract.View {
    @Inject
    MainActivityContract.Presenter mPresenter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mPresenter.attach();
    }

    @Override
    public void setText(String text) {
        ((TextView) findViewById(R.id.example_text)).setText(text);
    }
}

演示者代码:

public class MainActivityPresenter implements MainActivityContract.Presenter {

    private MainActivityContract.View mView;

    @Inject
    public MainActivityPresenter(MainActivityContract.View view) {
        mView = view;
    }

    public void attach() {
        this.mView.setText("Hello world!");
    }
}

普通匕首-android设置：

申请代码

public class MyApplication extends DaggerApplication {
    @Override
    protected AndroidInjector<? extends DaggerApplication> applicationInjector() {
        return DaggerAppComponent.builder().application(this).build();
    }
}

AppComponent

@Component(modules = {ActivityBindingModule.class, AndroidSupportInjectionModule.class})
public interface AppComponent extends AndroidInjector<MyApplication> {
    @Component.Builder
    interface Builder {
        @BindsInstance
        AppComponent.Builder application(Application application);

        AppComponent build();
    }
}

Activity绑定模块

@Module
public abstract class ActivityBindingModule {
    @ActivityScoped
    @ContributesAndroidInjector(modules = MainActivityModule.class)
    abstract MainActivity mainActivity();
}

现在我想将 activity 转换成片段。

重复上述模式，唯一不同的是片段代码：

public class ExampleFragment extends DaggerFragment implements ExampleFragmentContract.View {
    @Inject
    ExampleFragmentContract.Presenter mPresenter;

    @Inject
    public ExampleFragment() {

    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.example_fragment, container, false);
    }

    @Override
    public void setText(String text) {
        ((TextView) getView().findViewById(R.id.example_text)).setText(text);
    }
}

Main Activity 变笨了，演示者被删除了：

public class MainActivity extends DaggerAppCompatActivity {
    @Inject
    ExampleFragment exampleFragment;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        fragmentTransaction.add(R.id.root, exampleFragment);
    }
}

模块保留，但现在注入片段：

@Module
public abstract class MainActivityModule {
    @FragmentScoped
    @ContributesAndroidInjector(modules = ExampleFragmentModule.class)
    abstract ExampleFragment exampleFragment();
}

现在编译失败并出现错误：

Error:(13, 8) error: [dagger.android.AndroidInjector.inject(T)] com.example.michael.daggerfragmentexample.ui.ExampleFragment.ExampleFragmentContract.Presenter cannot be provided without an @Provides-annotated method.
com.example.michael.daggerfragmentexample.ui.ExampleFragment.ExampleFragmentContract.Presenter is injected at
com.example.michael.daggerfragmentexample.ui.ExampleFragment.ExampleFragment.mPresenter
com.example.michael.daggerfragmentexample.ui.ExampleFragment.ExampleFragment is injected at
com.example.michael.daggerfragmentexample.ui.MainActivity.MainActivity.exampleFragment
com.example.michael.daggerfragmentexample.ui.MainActivity.MainActivity is injected at
dagger.android.AndroidInjector.inject(arg0)
A binding with matching key exists in component: com.example.michael.daggerfragmentexample.ui.MainActivity.MainActivityModule_ExampleFragment.ExampleFragmentSubcomponent

在我看来，我有两层深的子组件，而匕首忽略了更深的模块。这是我做不到的吗？

Link to the full sample code.

Answer 1

在您的 ExampleFragmentPresenter 中，您缺少范围界定

@FragmentScoped
public class ExampleFragmentPresenter implements ExampleFragmentContract.Presenter

此外，您正在尝试将片段作用域注入添加到来自 MainActivity

的 activity 作用域中

@Inject
ExampleFragment exampleFragment;

这是错误的，因为您的 activity 作用域对您的片段注入一无所知，所以另外还要这样做：

public class MainActivity extends DaggerAppCompatActivity {

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        fragmentTransaction.add(R.id.root, ExampleFragment.newInstance());
    }
}

// removed @Inject here
public ExampleFragment() {

}

如何使用 dagger-android 与演示者相互 link 片段？

How to mutually link fragments with presenters using dagger-android?

android

android-fragments

mvp

dagger-2

dagger