Dagger 2 ContributesAndroidInjector 提供 activity 给模块

Question

我正在尝试找出一种更少样板的方法来实现我所有应用程序活动中使用的 ActivityModule。这是我当前的设置：

ActivityModule:

@Module
class ActivityModule(private val activity: Activity) {

    @Provides @ActivityScope
    fun providesActivity(): Activity = activity

    @Provides @ActivityContext @ActivityScope
    fun providesContext(): Context = activity

    @Provides @ActivityContext @ActivityScope
    fun providesLayoutInflater(): LayoutInflater = activity.layoutInflater

    @Provides @ActivityContext @ActivityScope
    fun providesResources(): Resources = activity.resources

}

AppActivityModule（为AndroidInjectionModule提供活动）

@Module(subcomponents = [
        AppActivityModule.WelcomeActivityComponent::class
    ])
    internal abstract class AppActivityModule {

        @Binds 
        @IntoMap 
        @ActivityKey(WelcomeActivity::class)
        abstract fun bindWelcomeActivityInjectorFactory(builder: WelcomeActivityComponent.Builder): AndroidInjector.Factory<out Activity>

        @ActivityScope
        @Subcomponent(modules = [(ActivityModule::class)])
        interface WelcomeActivityComponent : AndroidInjector<WelcomeActivity> {
        @Subcomponent.Builder abstract class Builder : AndroidInjector.Builder<WelcomeActivity>() {
            abstract fun activityModule(myActivityModule: ActivityModule): AndroidInjector.Builder<WelcomeActivity>

            override fun seedInstance(instance: WelcomeActivity) {
                activityModule(ActivityModule(instance))
            }
        }
    }
}

我想要的 AppActivityModule 是：

@Module
internal abstract class AppActivityModule {
    @ContributesAndroidInjector(modules = [(ActivityModule::class)])
    abstract fun contributeWelcomeActivityInjector(): WelcomeActivity
}

但是，这很容易理解，给了我一个错误 /di/AppActivityModule_ContributeWelcomeActivityInjector.java:29: error: @Subcomponent.Builder is missing setters for required modules or subcomponents: [...di.modules.ActivityModule]

我的问题是 - 是否有更简单的样板式方法来实现我想要做的事情？我知道 @Bind 和 @BindsInstance（来自 this answer），但这似乎只有在我有一个模块每个 activity 并绑定具体的 activity 类型时才有效在这种情况下我不想要 - 我希望 ActivityModule 处理所有活动。

Answer 1

最小化样板文件的一种方法是制作一个通用 Activity 模块，然后根据 Activity.

创建一个小的特定模块

// Abstract class so you don't have to provide an instance
@Module
abstract class ActivityModule {

    // No need for ActivityScope: You're always binding to the same Activity, so
    // there's no reason to have Dagger save your Context instance in a Provider.
    @Binds @ActivityContext
    abstract fun providesContext(activity: Activity): Context

    // This doesn't *have* to be in a companion object, but that way
    // Android can do a static dispatch instead of a virtual method dispatch.
    // If you don't need that, just skip the constructor arguments and make these
    // normal methods and you'll be good to go.
    companion object {
        @Provides @ActivityContext
        fun providesLayoutInflater(activity: Activity): LayoutInflater = 
            activity.layoutInflater

        @Provides @ActivityContext
        fun providesResources(activity: Activity): Resources = activity.resources
    }
}

（在 2.26 之前的 Dagger 版本中，您可能需要在 companion 对象上添加 @Module 并在您的 @Provides 方法上添加 @JvmStatic，如 2020 年 1 月的 this previous revision. Since Dagger 2.26 中，这些不是必需的。谢谢arekolek！）

你的模块：

@Module
internal abstract class AppActivityModule {

    @Module
    internal interface WelcomeActivityModule {
      // The component that @ContributesAndroidInjector generates will bind
      // your WelcomeActivity, but not your Activity. So just connect the two,
      // and suddenly you'll have access via injections of Activity.
      @Binds fun bindWelcomeActivity(activity: WelcomeActivity) : Activity
    }

    @ContributesAndroidInjector(
        modules = [ActivityModule::class, WelcomeActivityModule::class])
    abstract fun contributeWelcomeActivityInjector(): WelcomeActivity
}

请注意，虽然这适用于 Activity、Service、BroadcastReceiver 和其他，但您可能不希望对 Fragment 这么快。这是因为 dagger.android 处理具有父片段的片段层次结构，因此您可以从子组件中访问 YourApplication、YourActivity、YourParentFragment 和 YourChildFragment 及其所有组件。如果 YourChildFragmentComponent 中的某些内容依赖于不合格的 Fragment，那么它是否真正需要 YourParentFragment 或 YourChildFragment 将是不明确的。也就是说，这种设计对于Activity和某些Fragment确实有意义，所以（谨慎）使用它是有意义的。

编辑： @ActivityContext 在这里做什么？

@ActivityContext这里以qualifier annotation you'd define, which you can use to distinguish bindings of the same type in Dagger and other DI framework, presumably @ApplicationContext Context vs @ActivityContext Context. It would work to leave it out to try it, but I heavily recommend keeping it and avoiding binding an unqualified Context: Application and Activity contexts may be different, particularly in multi-screen or auto environments, and to get the right resources and data you should be precise about which you use. You can use this one为例

Dagger 2 ContributesAndroidInjector 提供 activity 给模块

Dagger 2 ContributesAndroidInjector provide activity to module

java

android

kotlin

dagger

dagger-2