android - Dagger 2 - 将 FragmentManager 传递给构造函数

Question

我正在研究 Dagger 2 库并遇到传递无法从“扩展应用程序”类获取的参数的问题。

例如，我需要将 FragmentManager 传递给 ViewPager 适配器构造函数。 你会怎么做？

我的申请:

public class MyApplication extends Application {

private MyAppComponent mMyAppComponent;

@Override
public void onCreate() {
    super.onCreate();

    Context context = getApplicationContext();

    mMyAppComponent= DaggerMyAppComponent.builder()
            .utilityModule(new UtilityModule())
            .locationModule(new LocationModule(context))
            .appModule(new AppModule(context))
            .pagerAdapterModule(new PagerAdapterModule(context)) //this one is problematic
            .build();
}

public MyAppComponent getmMyAppComponent() {
    return mMyAppComponent;
    }
}

我的应用组件:

@Singleton
@Component(
    modules = {
            UtilityModule.class,
            LocationModule.class,
            PagerAdapterModule.class,
            AppModule.class
    }

)

public interface MyComponent {
    FragmentManager fragmentManager(); //is it right?

    public void inject(NavigationActivity navigationActivity);
}

应用模块:

@Module
public class AppModule {
Context context;

public AppModule(Context context) {
    this.context = context;
}

@Provides
@Singleton
Context provideApplicationContext() {
    return context;
    }
}

PagerAdapterModule:

@Module
public class PagerAdapterModule {
Context context;

public PagerAdapterModule(Context context) {
    this.context = context;
}

@Provides
@Singleton TabsPagerAdapter provideTabsPagerAdapter(FragmentManager fragmentManager) {
    return new TabsPagerAdapter(context, fragmentManager);
    }
}

导航 Activity :

@Inject TabsPagerAdapter mTabsAdapter; //I want this to be initialized 

Answer 1

您需要有一个FragmentActivity 才能获得一个FragmentManager，这意味着您无法在Application 级别完成它，因为它太早了。因此，您必须从 AppComponent 创建一个组件依赖项，我们将其命名为 ActivityComponent，它将看到 AppComponent 提供的所有依赖项。

@Component(modules = ActivityModule.class, dependencies = MyAppComponent.class)
public interface ActivityComponent {
    void inject(MainActivity mainActivity);
}

@Module
public class ActivityModule {

    FragmentActivity activity;

    public ActivityModule(FragmentActivity activity) {
        this.activity = activity;
    }

    @Provides
    TabsPagerAdapter provideTabsPagerAdapter() {
        return new TabsPagerAdapter(activity, activity.getSupportFragmentManager());
    }
}

现在在您 Activity 的 onCreate() 中:

public class MainActivity extends AppCompatActivity {

    @Inject
    TabsPagerAdapter tabsPagerAdapter;

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

        ActivityComponent activityComponent = DaggerActivityComponent.builder()
                                                .activityModule(new ActivityModule(this))
                                                .myAppComponent(MyApplication.getMyAppComponent())
                                                .build();

        activityComponent.inject(this);
    }

}