Android使用@contributesandroidinjector在片段内注入依赖项(Dagger2)

Question

@Inject
lateinit var mainTripsFragmentAdapter: MainTripsFragmentAdapter

我得到以下生成错误：

错误：[dagger.android.androidinjector.inject(T)]没有@provides-annotated方法，无法提供android.support.v4.app.fragmentManager。
公共抽象接口AppComponent扩展dagger.android.androidinjector{^android.support.v4.app.fragmentManager在com.example.presenters.main.trips.maintrips.fragmentManager注入。（fragmentManager,example.presenters.main.mainactivity.tripsfragment com.example.presenters.main.mainactivity在dagger.android.androidinjector.inject(arg0)组件中存在具有匹配键的绑定:com.example.di.fragmentbuilder_bindmaintRipsfragment$app_debug.maintRipsfragmentsubcomponent

我研究了3天，看了很多文章，但我不知道问题出在哪里！
我会发布相关代码，如果太长了，对不起

class MainTripsFragment @Inject constructor() : BaseFragment() {

    @Inject
    lateinit var mainTripsFragmentAdapter: MainTripsFragmentAdapter

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        pager.adapter = mainTripsFragmentAdapter
    }
}

BaseFragment：

abstract class BaseFragment : DaggerFragment() {

    override fun onAttach(context: Context?) {
        AndroidSupportInjection.inject(this)
        super.onAttach(context)
    }

    override fun onCreateView(
            inflater: LayoutInflater,
            container: ViewGroup?,
            savedInstanceState: Bundle?
    ): View? = inflater.inflate(getLayout(), container, false)

    abstract fun getLayout(): Int
}

以下是fragmentPagerAdapter:

class MainTripsFragmentAdapter @Inject constructor(
    fragmentManager: FragmentManager,
    private val mainCurrentTripsFragment: MainCurrentTripsFragment,
    private val mainHistoryTripsFragment: MainHistoryTripsFragment
) : FragmentPagerAdapter(fragmentManager) {

    override fun getItem(position: Int) = when (position) {
        0 -> mainCurrentTripsFragment
        1 -> mainHistoryTripsFragment
        else -> mainCurrentTripsFragment
    }

    override fun getCount() = 2
}

下面是与DI相关的类：

@Singleton
@Component(modules = [
    AndroidInjectionModule::class,
    ActivityBuilder::class,
    FragmentBuilder::class
])

interface AppComponent : AndroidInjector<DaggerApplication> {

    fun inject(app: App)

    override fun inject(instance: DaggerApplication)

    @Component.Builder
    interface Builder {
        @BindsInstance
        fun application(app: Application): Builder

        fun build(): AppComponent
    }
}

@Module
abstract class FragmentBuilder {

    @ContributesAndroidInjector
    internal abstract fun bindMainHomeFragment(): MainHomeFragment

    @Module
    internal interface MainTripsFragmentModule {

        @Binds
        fun bindMainTripsFragment(fragment: MainTripsFragment): Fragment
    }

    @ContributesAndroidInjector(modules = [FragmentModule::class, MainTripsFragmentModule::class])
    internal abstract fun bindMainTripsFragment(): MainTripsFragment

    @ContributesAndroidInjector
    internal abstract fun bindMainCurrentTripsFragment(): MainCurrentTripsFragment
    @ContributesAndroidInjector
    internal abstract fun bindMainHistoryTripsFragment(): MainHistoryTripsFragment
}

@Module
class FragmentModule {

    @Provides
    fun provideFragmentManager(fragment: Fragment) = fragment.childFragmentManager
}

@Module
abstract class ActivityBuilder {

    @ContributesAndroidInjector
    internal abstract fun contributeMainActivity(): MainActivity
}

class MainActivity : BaseActivity() {

     @Inject
     lateinit var tripsFragment: MainTripsFragment

     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)

         showFragment(tripsFragment)
     }

     private fun showFragment(fragment: Fragment) {
         supportFragmentManager
                 .beginTransaction()
                 .replace(R.id.layout_container, fragment)
                 .commit()
     }
 }

BaseActivity：

@SuppressLint("Registered")
abstract class BaseActivity : AppCompatActivity(), HasSupportFragmentInjector {

@Inject
lateinit var fragmentInjector: DispatchingAndroidInjector<Fragment>

    override fun onCreate(savedInstanceState: Bundle?) {
        AndroidInjection.inject(this)
        super.onCreate(savedInstanceState)
    }
    override fun supportFragmentInjector() = fragmentInjector
}

应用程序类：

class App : Application(), HasActivityInjector {
    @Inject
    lateinit var activityInjector: DispatchingAndroidInjector<Activity>

    override fun activityInjector(): AndroidInjector<Activity> = activityInjector

    override fun onCreate() {
        super.onCreate()

        DaggerAppComponent.builder()
                .application(this)
                .build()
                .apply {
                    inject(this@App)
                }

    }
}

其中一点是，如果我在活动中@injectPagerAdapter（我还应该为它添加一个模块），它工作得很好。
哪个部分实现错误？

Answer 1

这里有一些问题：

class MainTripsFragmentAdapter @Inject constructor(
    fragmentManager: FragmentManager,
    private val mainCurrentTripsFragment: MainCurrentTripsFragment,
    private val mainHistoryTripsFragment: MainHistoryTripsFragment
) : FragmentPagerAdapter(fragmentManager) {

    override fun getItem(position: Int) = when (position) { 
        0 -> mainCurrentTripsFragment  //no!!
        1 -> mainHistoryTripsFragment
        else -> mainCurrentTripsFragment
    }

    override fun getCount() = 2
}

getitem在PagerAdapter中表示“创建项”。当您使用PagerAdapter时，您将片段的创建委托给适配器。您不应该编写代码来缓存和存储片段，这是fragmentManager的工作。

相反，您的fragmentadapter应该如下所示：

    override fun getItem(position: Int) = when (position) { 
        0 -> MainCurrentTripsFragment.instantiate()
        1 -> MainHistoryTripsFragment.instantiate()
        else -> MainCurrentTripsFragment.instantiate()
    }

class MainCurrentTripsFragment: Fragment() {
    companion object {
        @JvmStatic
        fun instantiate(args: Bundle?) {
            val frag = MainCurrentTripsFragment()
            frag.arguments = args
        }
    }
}