Java Dagger 2：没有@Provides-annotated 方法就不能提供
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/43116825/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Dagger 2: Cannot be provided without an @Provides-annotated method
提问by hanchen ke
I just started learning dagger2 and faced strange issue that looks like a bug to me. Here's the module:
我刚开始学习 dagger2 并遇到了对我来说看起来像是一个错误的奇怪问题。这是模块：
@Module
public class SimpleModule {
@Provides
Cooker providerCooker() {
return new Cooker("tom", "natie");
}
}
Component:
成分：
@Component(modules = SimpleModule.class)
public interface SimpleComponent {
void inject(DaggerTestActivity activity);
}
Interface:
界面：
public interface CoffeeMaker {
String makeCoffee();
}
Implementation:
执行：
public class SimpleMaker implements CoffeeMaker {
Cooker mCooker;
@Inject
public SimpleMaker(Cooker cooker) {
this.mCooker = cooker;
}
@Override
public String makeCoffee() {
return mCooker.makeCoffee();
}
}
Cooker :
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;
}
}
Coffee machine:
咖啡机：
public class CoffeeMachine {
CoffeeMaker mMaker;
@Inject
public CoffeeMachine(CoffeeMaker coffeeMaker) {
this.mMaker = coffeeMaker;
}
public String makeCoffee() {
return mMaker.makeCoffee();
}
}
Just it. I use in the activit. Faced strange issue here:
只是它。我在活动中使用。在这里遇到奇怪的问题：
@Inject
CoffeeMachine mCoffeeMachine;
Error I'm getting from the Dagger 2 compiler is the following:
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.<init>(com.wyyc.daggertest.CoffeeMaker coffeeMaker)
All this situation looks very strange, and I'd like to hear some input from more experienced Dagger 2 users.
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。
采纳答案by azizbekian
Your CoffeeMachineneeds CoffeeMaker. And you have declared that Dagger will take care of providing that dependency to the CoffeeMachineby annotating the constructor with @Inject. But Dagger says:
您的CoffeeMachine需求CoffeeMaker。并且您已经声明 Dagger 将CoffeeMachine通过使用 注释构造函数来负责向 提供该依赖项@Inject。但是匕首说：
CoffeeMaker cannot be provided without an @Provides-annotated method
如果没有@Provides 注释的方法，则无法提供 CoffeeMaker
Because you haven't specified anywhere how CoffeeMakerobject should be created. @Injecting SimpleMakeris not enough, because SimpleMaker!= CoffeeMaker. So, you have to specify explicitly, that when Dagger wants CoffeeMakerthen provide him SimpleMaker.
因为您没有在任何地方指定CoffeeMaker应该如何创建对象。@InjectingSimpleMaker是不够的，因为SimpleMaker!= CoffeeMaker。因此，您必须明确指定，当 Dagger 想要时CoffeeMaker再提供他SimpleMaker。
Change your module to this:
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);
}
}
