[Android][Framework] 添加系统服务

做系统开发，有时候需要自己定义一些接口供App使用， 同时为了方便维护管理，就会需要自己建立一个服务，把新的功能集中在一起。下面就是新建一个系统服务的基本步骤。

1. 添加接口

frameworks/base/core/java/android/app/IDemoManager.aidl

package android.app;

interface IDemoManager

{

   int getCpuTemperature();

}

1. 添加服务，实现aidl文件定义的接口

frameworks/base/services/core/java/com/android/server/DemoManagerService.java

package com.android.server;

import android.app.IDemoManager;

import android.content.Context;

import android.util.Slog;

public class DemoManagerService extends IDemoManager.Stub {

   private Context mContext;

   public DemoManagerService(Context context) {

       mContext = context;

       Slog.d("Demo", "Construct");

   }

   @Override

   public int getCpuTemperature() {

       return 100; // Test code

   }

}

1. 添加对应的Manager

frameworks/base/core/java/android/app/DemoManager.java

package android.app;

import android.content.Context;

import android.os.RemoteException;

import android.util.Slog;

public class DemoManager {

   Context mContext;

   IDemoManager mService;

   public DemoManager(Context context, IDemoManager service) {

       mContext = context;

       mService = service;

   }

   public int getCpuTemperature() {

       if (mService != null) {

           try {

               return mService.getCpuTemperature();

           } catch (RemoteException e) {

               Slog.e("Demo", "RemoteException " + e);

           }

       }

       return -1;

   }

}

1. 添加aidl到Makefile src

frameworks/base/Android.mk

LOCAL_SRC_FILES += \

   core/java/android/app/IDemoManager.aidl \

1. 添加DEMO_SERVICE常量

frameworks/base/core/java/android/content/Context.java

public static final String DEMO_SERVICE = "demo";

1. 注册系统服务

frameworks/base/core/java/android/app/SystemServiceRegistry.java

registerService(Context.ORISLINK_SERVICE, DemoManager.class,

   new CachedServiceFetcher<DemoManager>() {

       @Override

       public DemoManager createService(ContextImpl ctx) {

           IBinder b = ServiceManager.getService(Context.DEMO_SERVICE);

           return new DemoManager(ctx, IDemoManager.Stub.asInterface(b));

}});

1. 开机启动服务

frameworks/base/services/java/com/android/server/SystemServer.java

try {

   ServiceManager.addService(Context.DEMO_SERVICE, new DemoManagerService(context));

} catch (Throwable e) {

   Slog.e("Demo", "Failed to start Demo Service " + e);

}

1. 编译源码，因为添加了接口，所以需要

make update-api

更新接口。然后再整编刷机。

1. service list 查看服务，不存在，这是因为selinux权限没加。
2. 添加sepolicy权限

device/qcom/sepolicy/msm8937/service.te

type demo_service, system_api_service, system_server_service, service_manager_type;

device/qcom/sepolicy/msm8937/service_contexts

demo u:object_r:demo_service:s0

1. 重新编译代码，使用下面测试代码验证

```java

import android.app.DemoManager;

DemoManager om = (DemoManager) getSystemService(Context.DEMO_SERVICE);

Log.d(TAG, "Current temperature is " + om.getCpuTemperature());

```

最终log打印出100，服务添加完成。

个人博客

http://wossoneri.github.io/2018/09/15/Androidcreate-system-service/