0.基于Dager2.38.1的hilt源码-前言

佛学徒
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前言

想了解hilt源码必须对Dagger的使用有所了解，否则将会感觉说的云里雾里。

当前hilt源码在应用上相对来说比Dagger简化很多，所以使用方便。but，他还是转换成Dagger形式，所以从源码的角度来说做的比Dagger感觉还要多。代码理解起来自然不容易。

Dagger案例

先看下Dagger的案例，为下面的Hilt做一个铺垫。

@Module(subcomponents = Subcomponent1.class,Subcomponent2.class,Subcomponent3.class)
public class Module{
	@Provides
	@Singleton
	public A bindingMethod(B b){
		return new A(b);
	}
}

@Component(modules = Module.class)
public calss Component{
	inject(MembersInjector m);

	public SubcomponentX getSubcomponentX();//这个也是一个Subcomponent节点
}


public class MembersInjector{
	
	@Inject
	public C C;
}


@Singleton
public class C {
	

	@Inject
	public C(){}
}

hilt 使用Demo引发的不归路

实现声明：为了方便我们的理解，以下的代码是进过我个人简化再简化得来的案例。实际hilt源码比这个零散的多，而且理解困难的多。

hilt demo

demo地址，可自行查看

  1. 在Application（用户自定义，命名确实比较骚）使用@HiltAndroidApp修饰，Activity和Fragment使用@AndroidEntryPoint修饰：

     @HiltAndroidApp
 class Application : Application() {
 
     override fun onCreate() {
         super.onCreate()
         if (BuildConfig.DEBUG) {
             Timber.plant(Timber.DebugTree())
         }
     }
 
 }

 @AndroidEntryPoint
 class MainActivity : AppCompatActivity(R.layout.activity_main)


 @AndroidEntryPoint
 class UserListFragment : Fragment() {...}

 @AndroidEntryPoint
 class UserDetailsFragment : Fragment() {...}

  2. viemodel上使用了@HiltViewModel修饰:

     @HiltViewModel
 class UserListViewModel @Inject constructor(
     private val userListRepository: UserListRepository
 ) : ViewModel() {...}

 @HiltViewModel
 class UserDetailsViewModel @Inject constructor(
     private val userDetailsRepository: UserDetailsRepository
 ) : ViewModel() {...}

  3. 这样操作就可以使用和Dagger一样注解了，DatabaseModule和NetworkModule；

     @InstallIn(SingletonComponent::class)
 @Module
 object DatabaseModule {
     @Provides
     @Singleton
     fun provideAppDatabase(@ApplicationContext appContext: Context): UsersDatabase {
         return Room.databaseBuilder(
             appContext,
             UsersDatabase::class.java,
             "Users"
         ).fallbackToDestructiveMigration().build()
     }
 
     @Provides
     fun provideChannelDao(usersDatabase: UsersDatabase): UsersDao {
         return usersDatabase.usersDao
     }
 
 }

 @Module
 @InstallIn(SingletonComponent::class)
 object NetworkModule {
 
     @Singleton
     @Provides
     fun provideOkHttpClient() = if (BuildConfig.DEBUG) {
         val loggingInterceptor = HttpLoggingInterceptor()
         loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY)
         OkHttpClient.Builder()
             .addInterceptor(loggingInterceptor)
             .build()
     } else {
         OkHttpClient
             .Builder()
             .build()
     }
 
     @Singleton
     @Provides
     fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit = Retrofit.Builder()
         .addConverterFactory(MoshiConverterFactory.create())
         .baseUrl("https://api.github.com/")
         .client(okHttpClient)
         .build()
 
     @Provides
     @Singleton
     fun provideApiService(retrofit: Retrofit): UserListService =
         retrofit.create(UserListService::class.java)
 
     @Provides
     @Singleton
     fun provideUserDetailsService(retrofit: Retrofit): UserDetailsService =
         retrofit.create(UserDetailsService::class.java)
 
 }

是不是写法很简单，下面看看他到底是转换成什么样子的Dagger案例。看了估计得让人炸锅。

hilt转换成Dagger 案例

一.hilt源码将@HiltAndroidApp和@AndroidEntryPoint修饰的节点生成的接口

@HiltAndroidApp修饰的Application生成注入方法：

@OriginatingElement(
    topLevelClass = Application.class
)
@GeneratedEntryPoint
@InstallIn(SingletonComponent.class)
public interface Application_GeneratedInjector {
  void injectApplication(Application application);
}

@AndroidEntryPoint修饰的MainActivity生成注入方法：

@OriginatingElement(
    topLevelClass = MainActivity.class
)
@GeneratedEntryPoint
@InstallIn(ActivityComponent.class)
public interface MainActivity_GeneratedInjector {
  void injectMainActivity(MainActivity mainActivity);
}

@AndroidEntryPoint修饰的UserListFragment生成注入方法：

@OriginatingElement(
    topLevelClass = UserListFragment.class
)
@GeneratedEntryPoint
@InstallIn(FragmentComponent.class)
public interface UserListFragment_GeneratedInjector {
  void injectUserListFragment(UserListFragment userListFragment);
}

@AndroidEntryPoint修饰的UserDetailsFragment生成注入方法：

@OriginatingElement(
    topLevelClass = UserDetailsFragment.class
)
@GeneratedEntryPoint
@InstallIn(FragmentComponent.class)
public interface UserDetailsFragment_GeneratedInjector {
  void injectUserDetailsFragment(UserDetailsFragment userDetailsFragment);
}

二.hilt针对@HiltViewModel修饰的ViewModel子类的处理

@HiltViewModel修饰UserListViewModel生成代码,当前类作用看BindsModule类的binds方法：实例化UserListViewModel对象：

@OriginatingElement(
    topLevelClass = UserListViewModel.class
)
public final class UserListViewModel_HiltModules {
  private UserListViewModel_HiltModules() {
  }

  @Module
  @InstallIn(ViewModelComponent.class)
  public abstract static class BindsModule {
    private BindsModule() {
    }

    @Binds
    @IntoMap
    @StringKey("com.aregyan.github.views.userList.UserListViewModel")
    @HiltViewModelMap
    public abstract ViewModel binds(UserListViewModel vm);
  }

  @Module
  @InstallIn(ActivityRetainedComponent.class)
  public static final class KeyModule {
    private KeyModule() {
    }

    @Provides
    @IntoSet
    @HiltViewModelMap.KeySet
    public static String provide() {
      return "com.aregyan.github.views.userList.UserListViewModel";
    }
  }
}

@HiltViewModel修饰UserListViewModel生成代码,当前类作用看BindsModule类的binds方法：实例化UserDetailsViewModel对象：

@OriginatingElement(
    topLevelClass = UserDetailsViewModel.class
)
public final class UserDetailsViewModel_HiltModules {
  private UserDetailsViewModel_HiltModules() {
  }

  @Module
  @InstallIn(ViewModelComponent.class)
  public abstract static class BindsModule {
    private BindsModule() {
    }

    @Binds
    @IntoMap
    @StringKey("com.aregyan.github.views.userDetails.UserDetailsViewModel")
    @HiltViewModelMap
    public abstract ViewModel binds(UserDetailsViewModel vm);
  }

  @Module
  @InstallIn(ActivityRetainedComponent.class)
  public static final class KeyModule {
    private KeyModule() {
    }

    @Provides
    @IntoSet
    @HiltViewModelMap.KeySet
    public static String provide() {
      return "com.aregyan.github.views.userDetails.UserDetailsViewModel";
    }
  }
}

三.hilt提供的component节点

源码不是如下代码，这里是方便我们理解我这边单方面做的改动！！！后面代码如果看不懂，完全可以按照当下代码去理解。这里的代码对我们的理解非常非常非常重要！！！

请务必认真理解！！！

  1. SingleTonComponent节点：

     @Component(modules = [
 	DatabaseModule.class,
 	NetworkModule.class,
 	//自行去查看，比较简单的module节点
 	ApplicationContextModule.class
 ])
 @Singleton
 public static abstract class SingletonComponent 
 	implements Application_GeneratedInjector
 		
 {
 	
 	//Application_GeneratedInjector类中的方法
 	//void injectApplication(Application application);

 	ActivityRetainedComponentBuilder retainedComponentBuilder();
 		
 	@Component.Builder
 	public static interface Builder{
 		Builder applicationContextModule(ApplicationContextModule context);

 		SingletonComponent build();
 	}
 }
  • 以上代码应该很好理解吧。

  1. ActivityRetainedComponent类：

     @subComponent(modules = [
 	UserDetailsViewModel_HiltModules.KeyModule.class,
 	UserListViewModel_HiltModules.KeyModule.class,
 	//hilt源码
 	ActivityRetainedComponentManager.LifecycleModule.class,
 	
 ])
 @ActivityRetainedScoped
 public static abstract class ActivityRetainedComponent{

 	ActivityComponentBuilder activityComponentBuilder();

 	ActivityRetainedLifecycle getActivityRetainedLifecycle();
 		
 	@SubComponent.Builder
 	static interface Builder implements ActivityRetainedComponentBuilder{
 		
 		ActivityRetainedComponent build();
 	}
 }

  • （1）ActivityRetainedComponentManager.LifecycleModule提供bind方法，目的在于ActivityRetainedLifecycle对象的实例化是其子类Lifecycle；

  • （2）ActivityRetainedComponent类的getActivityRetainedLifecycle实际操作的是Lifecycle类；

  1. ActivityComponent类：

     @subComponent(modules = [
 	DefaultViewModelFactories.ActivityModule.class,
 	ActivityModule.class,
 ])
 @ActivityScoped
 public static abstract class ActivityComponent 
 	implements
 		MainActivity_GeneratedInjector
 {
 	//MainActivity_GeneratedInjector中的方法		
 	//void injectMainActivity(MainActivity mainActivity);
 	
 	InternalFactoryFactory getHiltInternalFactoryFactory();
 	
 	@HiltViewModelMap.KeySet
 	Set<String> getViewModelKeys();
 	
 	ViewModelComponentBuilder getViewModelComponentBuilder();
 	
 	FragmentComponentBuilder fragmentComponentBuilder();
 	
 	@SubComponent.Builder
 	static interface Builder implements ActivityComponentBuilder{
 		
 		ActivityComponentBuilder activity(
 				@BindsInstance
 						Activity activity);

 		ActivityComponent build();
 	}
 }

  • （1）实例化InternalFactoryFactory对象；

  • （2）getViewModelKeys方法收集UserListViewModel_HiltModules和UserDetailsViewModel_HiltModules中@HiltViewModelMap.KeySet修饰的方法返回类型；

  1. FragmentComponent类：

     @subComponent
 @FragmentScoped
 public static abstract class FragmentComponent 
 	implements
 		UserDetailsFragment_GeneratedInjector,
 		UserListFragment_GeneratedInjector
 {
 	//UserDetailsFragment_GeneratedInjector		
 	//void injectUserDetailsFragment(UserDetailsFragment userDetailsFragment);
 	
 	//UserListFragment_GeneratedInjector
 	//void injectUserListFragment(UserListFragment userListFragment);
 	
 	InternalFactoryFactory getHiltInternalFactoryFactory();
 	
 	@SubComponent.Builder
 	static interface Builder implements FragmentComponentBuilder{
 		
 		FragmentComponentBuilder fragment(@BindsInstance Fragment fragment);
 		FragmentComponent build();
 	}
 }

  2. ViewModelComponent类：

     @subComponent(modules = [
                 UserDetailsViewModel_HiltModules.BindsModule.class,
                 UserListViewModel_HiltModules.BindsModule.class,
                 HiltViewModelFactory.ViewModelModule.class
         ])
         @ViewModelScoped
         public static abstract class ViewModelComponent
                 implements 
         {

                 //HiltViewModelFactory.ViewModelFactoriesEntryPoint
                 @HiltViewModelMap
                 Map<String, Provider<ViewModel>> getHiltViewModelMap()

                 @SubComponent.Builder
                 static interface Builder implements ViewModelComponentBuilder{

                         ViewModelComponentBuilder savedStateHandle(@BindsInstance SavedStateHandle handle);

                         ViewModelComponent build();
                 }
         }

总结

我也知道这个是MVVM模式，但是我目前为止还没有针对该模式进行源码层面的研究，所以没有按照套路去理解，仅仅是hilt代码沉默的。

看的比较憋屈！！！总有一种拳头打到棉花上的感觉。这个理解完，在对hilt实际应用理解一下，就针对aac相关源码的理解。

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