匕首2：如何在运行时更改提供的依赖项

问题描述

为了学习Dagger 2，我决定重写我的应用程序，但我坚持为以下问题寻找合适的解决方案。

In order to learn Dagger 2 i decided to rewrite my application but I'm stuck with finding the proper solution for the following problem.

为此假设我们有一个名为 Mode 的接口：

For the purpose of this example let's assume we have an interface called Mode:

public interface Mode {
    Object1 obj1();

    //some other methods providing objects for app
}

和两个实现：
NormalMode 和 DemoMode 。

Mode存储在单例中，因此可以从应用程序中的任何位置进行访问。

Mode is stored in singleton so it could be accessed from anywhere within application.

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;
  }
}

NormalMode 在运行时切换为 DemoMode （比方说，当用户两次在后台单击Clickcs时）

The NormalMode is switched to DemoMode at runtime (let's say, when user clickcs on background couple of times)

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定义为Dagger 2模块的模式：

---

So first I got rid of the singleton and defined Modes as Dagger 2 modules:

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

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

现在方法 backgroundClicked5Times 而不是处理单例，我想在DAG中将 NormalModeModule 替换为 DemoModeModule 从现在开始，其他需要 Object1 的类将获得 DemoObject1 的实现。

Now in the method backgroundClicked5Times instead of dealing with singleton I would like to replace NormalModeModule with DemoModeModule in DAG so the other classes that need Object1 would get a DemoObject1 implementation from now on.

如何在Dagger中做到这一点？

How can I do that in Dagger?

预先感谢。

推荐答案

也许您可以考虑使用多重绑定？

Maybe you can consider using multibindings?

@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();
  }
}

以及使用模式时：

@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!
}

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