Dagger2允许注入为空 [英] Dagger2 allow injection to be null

问题描述

因此，简而言之，同一款应用程序我有很多口味，但略有不同.我想为所有口味分别添加一个导航器.我正在使用Dagger2，并且每种口味都有一个子组件，在该组件中，我仅为给定口味注入东西.所以我也想注入一个Navigator类.

So, in short, I have a lot of flavors of the same app with slight differences. I would like to add a Navigator for all flavors independently. I'm using Dagger2, and I have a sub component for each flavor where I inject things only for a given flavor. So I would like to inject a Navigator class too.

诀窍是，通用代码中的某些类也使用此导航器，并带有null检查.因此，如果它为null，则很好，但如果不为空，则执行x.

The trick is, that some of the classes in the common code use this navigator too, with a null check. So if it's null, fine, but if not then do x.

所以我想要一个像这样的字段:

So I'd like to have a field like:

@Inject @Nullable Navigator navigator;

如果没有类似这样的@Provides方法，Dagger会给我一个错误，但这正是我想要的，我希望@Provides进入子模块，但仍要注入通用代码库中.

Dagger gives me an error if there is no @Provides method for something like this, but that's exactly what I want, I want the @Provides to go in the submodules but still inject in the common code base.

我该如何实现?

推荐答案

要支持可为空的类型，您只需在 @Provides 方法上添加 @Nullable 批注返回可为null的类型，Dagger将接受它.

To support a nullable type you just have to add a @Nullable annotation on your @Provides method that returns the nullable type and Dagger will accept it.

如果不这样做，Dagger会抱怨您只能从带有 @Nullable 注释的方法中提供可为空的类型.

If you don't, Dagger will complain that you can only provide nullable types from @Nullable annotated methods.

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