@Binds/@IntoMap/@ClassKey的使用

下面是一个完整的 Dagger 多绑定映射(@IntoMap)示例，展示从定义到使用的全过程：

@Binds注解

@Binds：这是 Dagger 中的一个注解，用于声明某个抽象方法的返回类型是接口或抽象类，而方法的参数是其具体实现类！！！

@IntoMap

@IntoMap :将EngineService放入一个Map<Class<?>, CarService>集合中

1. 定义服务接口和实现

// 服务接口
public interface CarService {void start();
}// 引擎服务实现
public class EngineService implements CarService {@Injectpublic EngineService() {}@Overridepublic void start() {System.out.println("Engine started");}
}// 空调服务实现
public class AirConditioningService implements CarService {@Injectpublic AirConditioningService() {}@Overridepublic void start() {System.out.println("AC cooling started");}
}

2. 创建 Dagger 模块

import dagger.Binds;
import dagger.Module;
import dagger.multibindings.ClassKey;
import dagger.multibindings.IntoMap;@Module
public abstract class CarServiceModule {// 将 EngineService 绑定到 Map<Class, CarService>@Binds :EngineService是CarService的实现类@IntoMap :将EngineService放入一个Map<Class<?>, CarService>集合中@ClassKey(EngineService.class) :EngineService.class作为放入Map的键keyabstract CarService bindEngineService(EngineService impl);// 将 AirConditioningService 绑定到 Map@Binds@IntoMap@ClassKey(AirConditioningService.class)abstract CarService bindAirConditioningService(AirConditioningService impl);
}

3. 创建服务管理器

import javax.inject.Inject;
import java.util.Map;public class ServiceManager {private final Map<Class<?>, CarService> serviceMap;@Injectpublic ServiceManager(Map<Class<?>, CarService> serviceMap) {this.serviceMap = serviceMap;System.out.println("ServiceManager initialized with services: " + serviceMap.keySet());}public CarService getService(Class<?> serviceClass) {return serviceMap.get(serviceClass);}
}

4. 创建 Dagger 组件

import dagger.Component;@Component(modules = CarServiceModule.class)
public interface CarComponent {ServiceManager getServiceManager();// 可选：直接获取MapMap<Class<?>, CarService> getServiceMap();
}

5. 使用示例

public class CarApp {public static void main(String[] args) {// 创建Dagger组件CarComponent component = DaggerCarComponent.create();// 获取服务管理器ServiceManager manager = component.getServiceManager();// 使用服务CarService engine = manager.getService(EngineService.class);engine.start(); // 输出: Engine startedCarService ac = manager.getService(AirConditioningService.class);ac.start(); // 输出: AC cooling started// 直接获取MapMap<Class<?>, CarService> serviceMap = component.getServiceMap();System.out.println("Direct map access: " + serviceMap.keySet());}
}

6. 生成的 Dagger 代码 (简化版)

// DaggerCarComponent.java (自动生成)
public final class DaggerCarComponent implements CarComponent {private final Map<Class<?>, Provider<CarService>> serviceMapProvider;private DaggerCarComponent() {this.serviceMapProvider = createServiceMap();}private Map<Class<?>, Provider<CarService>> createServiceMap() {Map<Class<?>, Provider<CarService>> map = new HashMap<>();// 绑定EngineServiceProvider<EngineService> engineProvider = DoubleCheck.provider(EngineService_Factory.create());map.put(EngineService.class, (Provider)engineProvider);// 绑定AirConditioningServiceProvider<AirConditioningService> acProvider = DoubleCheck.provider(AirConditioningService_Factory.create());map.put(AirConditioningService.class, (Provider)acProvider);return Collections.unmodifiableMap(map);}@Overridepublic ServiceManager getServiceManager() {return new ServiceManager(MapProviderFactory.<Class<?>, CarService>create(serviceMapProvider).get());}@Overridepublic Map<Class<?>, CarService> getServiceMap() {return MapProviderFactory.<Class<?>, CarService>create(serviceMapProvider).get();}
}

输出结果

ServiceManager initialized with services: [class EngineService, class AirConditioningService]
Engine started
AC cooling started
Direct map access: {class EngineService=EngineService@1234, class AirConditioningService=AirConditioningService@5678}