Question

我正在使用以下Google示例项目：https://github.com/googlesamples/android-architecture-components作为我的新项目的参考，并且在尝试向项目添加第二个活动时遇到了困难。

这是编译时遇到的错误

Error:(22, 8) error: [dagger.android.AndroidInjector.inject(T)] com.apps.myapp.ui.common.MainActivity cannot be provided without an @Inject constructor or from an @Provides-annotated method. This type supports members injection but cannot be implicitly provided.
com.apps.myapp.ui.common.MainActivity is injected at
com.apps.myapp.ui.common.NavigationController.<init>(mainActivity)
com.apps.myapp.ui.common.NavigationController is injected at
com.apps.myapp.ui.addContacts.AddContactsFragment.navigationController
com.apps.myapp.ui.addContacts.AddContactsFragment is injected at
dagger.android.AndroidInjector.inject(arg0)
A binding with matching key exists in component: com.apps.myapp.di.ActivityModule_ContributeMainActivity.MainActivitySubcomponent

这是我的代码

ActivityModule

@Module
public abstract class ActivityModule {

    @ContributesAndroidInjector(modules = FragmentBuildersModule.class)
    abstract MainActivity contributeMainActivity();

    @ContributesAndroidInjector(modules = FragmentBuildersModule.class)
    abstract ContactActivity contributeContactActivity();
}

AppComponent

@Singleton
@Component(modules = {
        AndroidInjectionModule.class,
        AppModule.class,
        ActivityModule.class})
public interface AppComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance Builder application(Application application);
        AppComponent build();
    }
    void inject(App app);
}

AppInjector

public class AppInjector {
    private AppInjector() {}
    public static void init(App app) {DaggerAppComponent.builder().application(app).build().inject(app);
                    app.registerActivityLifecycleCallbacks(new Application.ActivityLifecycleCallbacks() {
                    @Override
                    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
                        handleActivity(activity);
                    }

                    @Override
                    public void onActivityStarted(Activity activity) {

                    }

                    @Override
                    public void onActivityResumed(Activity activity) {

                    }

                    @Override
                    public void onActivityPaused(Activity activity) {

                    }

                    @Override
                    public void onActivityStopped(Activity activity) {

                    }

                    @Override
                    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

                    }

                    @Override
                    public void onActivityDestroyed(Activity activity) {

                    }
                });
    }

    private static void handleActivity(Activity activity) {
        if (activity instanceof HasSupportFragmentInjector) {
            AndroidInjection.inject(activity);
        }
        if (activity instanceof FragmentActivity) {
            ((FragmentActivity) activity).getSupportFragmentManager()
                    .registerFragmentLifecycleCallbacks(
                            new FragmentManager.FragmentLifecycleCallbacks() {
                                @Override
                                public void onFragmentCreated(FragmentManager fm, Fragment f,
                                        Bundle savedInstanceState) {
                                    if (f instanceof Injectable) {
                                        AndroidSupportInjection.inject(f);
                                    }
                                }
                            }, true);
        }
    }
}

的AppModule

@Module(includes = ViewModelModule.class)
class AppModule {
    @Singleton @Provides
    BnderAPIService provideService() {
        return new Retrofit.Builder()
                .baseUrl("serverurl")
                .addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(new LiveDataCallAdapterFactory())
                .build()
                .create(APIService.class);
    }

    @Singleton @Provides
    Db provideDb(Application app) {
        return Room.databaseBuilder(app, Db.class,"Db.db").build();
    }

    @Singleton @Provides
    UserDao provideUserDao(Db db) {
        return db.userDao();
    }

    @Singleton @Provides
    ContactDao provideContactDao(Db db) {
        return db.contactDao();
    }
}

FragmentBuildersModule

@Module
public abstract class FragmentBuildersModule {

    @ContributesAndroidInjector
    abstract AddContactsFragment contributeAddUserFragment();

    @ContributesAndroidInjector
    abstract ContactsFragment contributeContactsFragment();

    @ContributesAndroidInjector
    abstract ChalkboardFragment contributeChalkboardFragment();
}

可注射

public interface Injectable {
}

ViewModelKey

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

ViewModelModule

@Module
abstract class ViewModelModule {
    @Binds
    @IntoMap
    @ViewModelKey(AddContactsViewModel.class)
    abstract ViewModel bindAddContactsViewModel(AddContactsViewModel addContactsViewModel);

    @Binds
    @IntoMap
    @ViewModelKey(ContactsViewModel.class)
    abstract ViewModel bindContactsViewModel(ContactsViewModel contactsViewModel);

    @Binds
    @IntoMap
    @ViewModelKey(ChalkboardViewModel.class)
    abstract ViewModel bindChalkboardViewModel(ChalkboardViewModel chalkboardViewModel);

    @Binds
    abstract ViewModelProvider.Factory bindViewModelFactory(ViewModelFactory factory);
}

应用

public class App extends Application implements HasActivityInjector {

    @Inject
    DispatchingAndroidInjector<Activity> dispatchingAndroidInjector;
    @Override
    protected void attachBaseContext(Context base) {
        super.attachBaseContext(base);
        MultiDex.install(this);
    }
    @Override
    public void onCreate() {
        super.onCreate();
        if (BuildConfig.DEBUG) {

        }
        AppInjector.init(this);
    }

    @Override
    public DispatchingAndroidInjector<Activity> activityInjector() {
        return dispatchingAndroidInjector;
    }
}

NavigationController

public class NavigationController {
    private final int containerId;
    private final FragmentManager fragmentManager;
    @Inject
    public NavigationController(MainActivity mainActivity) {
        this.containerId = R.id.container;
        this.fragmentManager = mainActivity.getSupportFragmentManager();
    }

    public void navigateToUsers() {
        Log.i("TAG", "Navigate to users");
        String tag = "users";
        AddContactsFragment userFragment = AddContactsFragment.create();
        fragmentManager.beginTransaction()
                .replace(containerId, userFragment, tag)
                .addToBackStack(null)
                .commitAllowingStateLoss();
    }

    public void navigateToContacts() {
        Log.i("TAG", "Navigate to contacts");
        String tag = "contacts";
        ContactsFragment contactsFragment = ContactsFragment.create();
        fragmentManager.beginTransaction()
                .add(contactsFragment, tag)
                .addToBackStack(null)
                .commitAllowingStateLoss();
    }

    public void navigateToChalkboard() {
        Log.i("TAG", "Navigate to chalkboard");
        String tag = "chalkboard";
        ChalkboardFragment chalkboardFragment = ChalkboardFragment.create();
        fragmentManager.beginTransaction()
                .add(chalkboardFragment, tag)
                .addToBackStack(null)
                .commitAllowingStateLoss();
    }
}

MainActivity

public class MainActivity extends AppCompatActivity implements LifecycleRegistryOwner, HasSupportFragmentInjector {
    private final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this);
    @Inject
    DispatchingAndroidInjector<Fragment> dispatchingAndroidInjector;
    @Inject
    NavigationController navigationController;
    private Toolbar toolbar;
    @Override
    public LifecycleRegistry getLifecycle() {
        return lifecycleRegistry;
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setHandler(this);
        binding.setManager(getSupportFragmentManager());
        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }

    @Override
    public DispatchingAndroidInjector<Fragment> supportFragmentInjector() {
        return dispatchingAndroidInjector;
    }

    static class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

        @Override
        public int getCount() {
            return mFragmentList.size();
        }

        public void addFragment(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }

    @BindingAdapter({"handler"})
    public static void bindViewPagerAdapter(final ViewPager view, final MainActivity activity) {
        final ViewPagerAdapter adapter = new ViewPagerAdapter(activity.getSupportFragmentManager());
        adapter.addFragment(new ChalkboardFragment(), "Chalkboard");
        adapter.addFragment(new ContactsFragment(), "Contacts");
        view.setAdapter(adapter);
    }

    @BindingAdapter({"pager"})
    public static void bindViewPagerTabs(final TabLayout view, final ViewPager pagerView) {
        view.setupWithViewPager(pagerView, true);
    }
}

ContactActivity

public class ContactActivity extends AppCompatActivity implements LifecycleRegistryOwner, HasSupportFragmentInjector {
    private final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this);
    @Inject
    DispatchingAndroidInjector<Fragment> dispatchingAndroidInjector;
    @Override
    public LifecycleRegistry getLifecycle() {
        return lifecycleRegistry;
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_contact);
        if (savedInstanceState == null) {

        }
    }

    @Override
    public DispatchingAndroidInjector<Fragment> supportFragmentInjector() {
        return dispatchingAndroidInjector;
    }
}

Answer 1

＆＃34;组件中存在具有匹配键的绑定＆＃34;意味着您已在整个对象图中的某处绑定了一个依赖项，但无法从需要注入它的子组件中访问它。这是javadoc：

实用程序代码，用于查找与绑定图中所有子组件中的键匹配的绑定，以便在当前子图中找不到绑定时，建议用户在其他位置存在绑定。如果匹配键的绑定存在于子组件或兄弟组件中，那通常是用户实际想要使用的。

例如，假设您有两个活动，ActivityA和ActivityB。您使用@ContributesAndroidInjector生成子组件并在ActivityA模块中绑定Foo，但不在ActivityB模块中绑定Foo。如果您在ActivityB中使用@Inject Foo foo请求git clone https://github.com/googlesamples/android-architecture-components.git`注入，则会收到该错误消息。

在您的特定情况下，您获得的错误可以通过以下方式重现：

从GitHub克隆项目
```
MainActivity
```
将ContactsActivity复制粘贴到新文件MainActivityModule
将ActivityModule修改为ActivityModule

因此，我们可以得出结论，您的@ContributesAndroidInjector存在问题。 ContributesAndroidInjector并不像看起来那么简单。它实际上意味着您要为您在其中指定的活动创建一个新的Dagger 2子组件（请参阅docs here）。

子组件可以使用父组件的绑定，但不能使用兄弟组件。 ActivityModule中MainActivity的两行代码创建了两个兄弟子组件：一个用于ContactsActivity，另一个用于NavigationController。

但是，MainActivity依赖于MainActivity，ContactsActivity绑定在AddContactsFragment子组件的对象图中，而不是ContactsActivity子组件的对象图中。 MainActivity已成为NavigationController子组件的对象图的一部分，并且无法再访问AddContactsFragment。这意味着当Dagger 2尝试在MainActivity内注入MainActivity时，它无法提供AndroidInjector作为它的依赖。这解释了＆＃34;无法提供＆＃34;部分错误信息。

虽然它无法在该特定对象图中提供MainActivity，但MainActivity.class 通常会知道MainActivityFactory因此错误消息＆＃34;存在绑定密钥＆＃34;。这有什么约束力？将ActivityModule绑定到@ContributesAndroidInjector的键。这个键的位置在哪里？在为MainActivity撰写NavigationController时MainActivity。{/ p>

如何解决这个问题超出了StackOverflow问题的范围，因为它涉及代码的冗长重构。您需要重新组织对象图，以便AppCompatActivity不再依赖ContributesAndroidInjector。也许你可以让它依赖于AppCompatActivity，因为那是你的两个活动的超类。然后，您需要停止使用NotificationManagerCompat并为包含NotificationCompat绑定的两个活动编写显式模块。

但是，现在请回到基础，并从更容易开始。这是一个灾难的秘诀，从一个复杂的项目开始，没有完全理解，只是修改它希望它可以工作。

Codepath Dagger 2 tutorial project更容易理解，让您熟悉Dagger 2中涉及的基本概念。一旦您熟悉了基本概念并理解了相关组件和子组件，那么您可以尝试一个更难的例子。祝你好运！

组件

1 个答案: