Dagger2:没有@Annex-annotated方法不能提供

我刚刚开始学习dagger2,面对一个看起来像个bug的奇怪问题.这是模块:

@Module
public class SimpleModule {

    @Provides
    Cooker providerCooker() {

        return new Cooker("tom", "natie");
    }
}

零件:

@Component(modules = SimpleModule.class)
public interface SimpleComponent {

    void inject(DaggerTestActivity activity);

}

接口:

public interface CoffeeMaker {

    String makeCoffee();
}

执行:

  public class SimpleMaker implements CoffeeMaker {

        Cooker mCooker;

        @Inject
        public SimpleMaker(Cooker cooker) {

            this.mCooker = cooker;

        }

        @Override
        public String makeCoffee() {

            return mCooker.makeCoffee();
        }
    }

电饭煲:

public class Cooker {

    String name; 
    String coffeeKind;


    public Cooker(String name, String coffeeKind) {
        this.name = name;
        this.coffeeKind = coffeeKind;
    }

   public  String  makeCoffee() {

        return name + "make" + coffeeKind; 
    }

}

咖啡机:

public class CoffeeMachine {

    CoffeeMaker mMaker;

    @Inject
    public CoffeeMachine(CoffeeMaker coffeeMaker) {

        this.mMaker = coffeeMaker;
    }

    public String makeCoffee() {

        return mMaker.makeCoffee();
    }
}

只是它.我在活动中使用.这里遇到奇怪的问题:

    @Inject
    CoffeeMachine mCoffeeMachine;

我从Dagger 2编译器得到的错误如下:

Error:(14, 10) com.wyyc.daggertest.CoffeeMaker cannot be provided without an @Provides-annotated method.
com.wyyc.zqqworkproject.DaggerTestActivity.mCoffeeMachine
[injected field of type: com.wyyc.daggertest.CoffeeMachine mCoffeeMachine]
com.wyyc.daggertest.CoffeeMachine.(com.wyyc.daggertest.CoffeeMaker coffeeMaker)

所有这些情况看起来都很奇怪,我想听听更有经验的Dagger 2用户的一些意见.

你的CoffeeMachine需求CoffeeMaker.而且你已经声明Dagger将负责CoffeeMachine通过注释构造函数来提供依赖性@Inject.但达格说:

如果没有@ Provide-annotated方法,则无法提供CoffeeMaker

因为您没有在任何地方指定CoffeeMaker应如何创建对象.@InjectING SimpleMaker是不够的,因为SimpleMaker!= CoffeeMaker.所以,你必须明确指出,当Dagger想要的CoffeeMaker时候提供给他SimpleMaker.

将您的模块更改为:

@Module
public class SimpleModule {

    @Provides
    Cooker providerCooker() {
        return new Cooker("tom", "natie");
    }

    @Provides
    CoffeeMaker provideCoffeeMaker(Cooker cooker) {
        return new SimpleMaker(cooker);
    }

}