Tutorial on how to add services to Android system

preface

Recently, because the company's platform is moving from Android 4.4.4 to Android 6.0, the problem is that we have added some services to the system before, so we need to migrate some system level services and some custom packages of the framework

I happened to see the patch of adding system services on Gerrit. It's just a summary. Although I'm not a framework engineer, it's good to know about Android system

How to obtain system services

We get the system services in the context and getsystemservice. Let's take a look at what happened to getsystemservice

The implementation of getsystemservice is contextimpl. Let's take a look at the source code of contextimpl

Android 4.4.4 (KitKat)

Here is the source code of Android 4.4.4 and 6.0. See it later

We also see many static code blocks in contextimpl. They are all registered services, and they are all our common system services

So, isn't this where we sign up for the service?

So. We found the place to register system services. Here, we just need to add the services we want to register and complete the abstract method of new servicefetcher(). In this way, we can get our service object by getsystemservice and passing in the name at the time of registration. Of course, this is the method of 4.4

Android 6.0 (Marshmallow)

Let's look at the code of contextimpl

We found that, unlike KitKat, marshmallow is obtained from a class called systemserviceregistry

Well, let's look at its source code. It's the same routine as before, but it encapsulates a class to manage these registered services. This design is really good. The coupling degree of the code looks much smaller, and it won't make the contextimpl class more and more bloated

So. Our marshmallow system service should be added to the systemserviceregistry class in the same way. Then we can get our service object by getsystemservice

summary

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