Dagger 2 - 如何使用@Inject标记类构造函数而不使用组件注册工作

Question

我的匕首已经设置了两个组件。一个组件是另一个重要组件的子组件。一切正常。但后来我随机想尝试构造函数注入，所以我创建了一个随机类，并用Inject注解标记了它的构造函数，当我想注入这个类时，我感到惊讶。我的组件对此一无所知。我没有写过关于这个类的组件接口。它只是一个随机类，它有一个用@Inject注解的构造函数。这是如何工作的？这里是随机类：

public class Knife { 

@Inject 
public Knife(){ 
    System.out.println("a spreading knife has been created"); 
}; 

}

，这里是如何调用注入我的课，如果该事项：

public class MainActivity extends AppCompatActivity { 

    private final String TAG = getClass().getSimpleName(); 

    //@Inject 
    //AlmondButter someAlmondButter; 
    @Inject 
    CashewSandwich sandwich; 

    @Inject 
    CashewSandwich sandwich2; 

/*some how this is getting injected but its not in any component, how ?No ones 
providing it in a module either*/ 
    @Inject 
    Knife mKnife; 

    SandwichComponent sandwichComponent; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     /*create the dependent butter for the sandwich here*/ 
     ButterComponent butterComponent=DaggerButterComponent.builder(). 
       butterModule(new ButterModule()).build(); 
     /*create a scope sandwichcomponent here */ 

     sandwichComponent=DaggerSandwichComponent.builder().sandwichModule(new SandwichModule()). 
       butterComponent(butterComponent) 
       .build(); 
     //finally we have a sandwichComponent, lets inject our dependencies 
     sandwichComponent.inject(this); 

     Log.v(TAG," first:"+sandwich.toString()); 
     Log.v(TAG,"second:"+sandwich2.toString()); 
     Log.v(TAG,mKnife.toString()); //this actually works ! 
    } 
    } 

更新：我写了一篇博客此功能柜面有人需要帮助： http://j2emanue.blogspot.ca/

Answer 1

在构造函数上放置@Inject使其对Dagger可检测。您可以在JSR 330中阅读更多关于它的信息。