Android Dagger依赖注入在私有字段上失败 [英] Android Dagger Dependency Injection fails on private Fields

问题描述

我是dagger的新手(尽管我有使用Weld开发Java EE WebApp的DI经验).

I'm new to dagger (though I have experience with DI from working on Java EE WebApps using Weld).

我想要做的是将依赖项注入到类中.该字段是私有的.

What I'm trying to do is to inject a dependency into a class. The field is private.

然后Dagger抛出一个异常，说明它无法注入私有字段.

Dagger then throws an exception stating it can't inject into a private field.

这是什么原因?

毕竟，即使在android上，也可以使用反射写入私有字段.

After all it is possible to write to private fields using reflections, even on android..

如果我将字段的可见性设置为非私有，则注入似乎有效.

If I set the visibility of the field to something other than private the injection seems to work.

推荐答案

使私有字段包可见"可能并不总是您想要的. Dagger文档提出以下建议:

Making a private field 'package visible' may not always be what you want. The Dagger documentation suggests the following:

注入最终字段和私有成员.为了获得最佳性能 匕首生成代码.通过使用构造函数来解决此问题 注射.

Injecting final fields and private members. For best performance Dagger generates code. Work around this by using constructor injection.

这是一个例子:

private ItemFactoryImpl itemFactory;
private BuildingFactory buildingFactory;

@Inject
public World(ItemFactoryImpl itemFactory, BuildingFactory buildingFactory) {
    this.itemFactory = itemFactory;
    this.buildingFactory = buildingFactory;
}

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