问题描述
我想了解 RoomDatabase 幕后发生的事情，它要求 DAO 是一个接口或一个抽象类.我已经搜索了很长时间，但所有文章和文档都只解释了方法，而不是原因.
I want to understand what is happening behind the scenes in a RoomDatabase, that it requires the DAO to be either an interface or an abstract class.I've been searching for quite a while, but all articles and documentation only explain the how, not the why.
推荐答案
不只是 Room，Retrofit 和其他库也使用这种模式，它被称为编程接口.而不是仅仅创建一个具体的实现，您只需指定您想要做的事情，他们就会为您提供一个将按照您的要求运行的实现.
It is not just the Room, Retrofit and other libraries use this pattern too, it is called Programming to an Interface.Instead of just creating a concrete implementation you just specify the stuff you want to do and they provide you with an implementation that will behave as you requested.
要进一步学习，您可以查看这篇文章:https://tuhrig.de/programming-to-an-interface/
For further study you can check this article:https://tuhrig.de/programming-to-an-interface/
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