Dagger 2:如何在运行时更改提供的依赖项

Question

为了学习Dagger 2,我决定重写我的应用程序,但我仍然坚持为以下问题找到合适的解决方案.

出于这个例子的目的,让我们假设我们有一个名为的接口Mode:

public interface Mode {
    Object1 obj1();

    //some other methods providing objects for app
}

和两个实现: NormalMode和DemoMode.

模式存储在单例中,因此可以从应用程序中的任何位置访问.

public enum ModeManager {
  INSTANCE,;

  private Mode mode;

  public Mode mode() {
    if (mode == null)
      mode = new NormalMode();
    return mode;
  }

  public void mode(Mode mode) { //to switch modules at runtime
    this.mode = mode;
  }
}

在NormalMode切换到DemoMode在运行时(比方说,当背景几次用户clickcs)

public void backgroundClicked5Times(){
  ModeManager.INSTANCE.mode(new DemoMode());
  //from now on every object that uses Mode will get Demo implementations, great!
}

---

所以首先我摆脱了单例并将模式定义为Dagger 2模块:

@Module
public class NormalModeModule {
  @Provides
  public Object1 provideObject1() {
    return new NormalObject1();
  }
}

@Module
public class DemoModeModule {
  @Provides
  public Object1 provideObject1() {
    return new DemoObject1();
  }
}

现在在方法中backgroundClicked5Times而不是处理单例我想在DAG中替换NormalModeModule,DemoModeModule所以其他需要的类从现在开始Object1就会得到一个DemoObject1实现.

我怎么能在Dagger那样做？

提前致谢.

Answer 1

也许您可以考虑使用多重绑定？

@Module
public class NormalModeModule {
  @Provides
  @IntoMap
  @StringKey("normal")
  public Object1 provideObject1() {
    return new NormalObject1();
  }
}

@Module
public class DemoModeModule {
  @Provides
  @IntoMap
  @StringKey("demo")
  public Object1 provideObject1() {
    return new DemoObject1();
  }
}

当使用模式时：

@Inject
Map<String, Mode> modes;
//or you perfer lazy initialization:
Map<String, Provider<Mode>> modes;

public void backgroundClicked5Times(){
  ModeManager.INSTANCE.mode(modes.get("demo"));
  //if you are using Provider:
  ModeManager.INSTANCE.mode(modes.get("demo").get());
  //from now on every object that uses Mode will get Demo implementations, great!
}

Answer 2

在对 dagger 进行了一段时间的实验后，我想出了在我的用例中似乎运行良好的解决方案。

1. 定义将保存有关模式的状态信息的类

   public class Conf {
     public Mode mode;
   
     public Conf(Mode mode) {
       this.mode = mode;
     }
   
     public enum Mode {
       NORMAL, DEMO
     }
   }
   

2. Conf在模块中提供单例实例

   @Module
   public class ConfModule {
     @Provides
     @Singleton
     Conf provideConf() {
       return new Conf(Conf.Mode.NORMAL);
     }
   }
   

3. 将模块添加到 AppComponent

   @Singleton
   @Component(modules = {AppModule.class, ConfModule.class})
   public interface AppComponent {
       //...
   }
   

4. 定义根据Mode提供不同对象的模块

   @Module
   public class Object1Module {
   
     @Provides
     Object1 provideObject1(Conf conf) {
       if (conf.mode == Conf.Mode.NORMAL)
         return new NormalObject1();
       else
         return new DemoObject1();
     }
   }
   

5. 要在运行时切换模式，只需注入Conf对象并修改它：

   public class MyActivity extends Activity {
       @Inject Conf conf;
   
       //...
   
       public void backgroundClicked5Times(){
           conf.mode = Conf.Mode.DEMO;
   
           //if you have dagger objects in this class that depend on Mode
           //execute inject() once more to refresh them
       }
   }