[Android][Framework] 添加系統服務

新博客地址
http://wossoneri.github.io/2018/09/15/[Android][Framework]create-system-service/

做系統開發，有時候需要自己定義一些介面供App使用， 同時為了方便維護管理，就會需要自己建立一個服務，把新的功能集中在一起。下麵就是新建一個系統服務的基本步驟。

1. 添加介面

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

   package android.app;
   
   interface IDemoManager
   {
       int getCpuTemperature();
   }

2. 添加服務，實現aidl文件定義的介面

   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
       }
   }

3. 添加對應的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;
       }
   }

4. 添加aidl到Makefile src

   frameworks/base/Android.mk

   LOCAL_SRC_FILES += \
       core/java/android/app/IDemoManager.aidl \

5. 添加DEMO_SERVICE常量

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

   public static final String DEMO_SERVICE = "demo";

6. 註冊系統服務

   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));
   }});

7. 開機啟動服務

   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);
   }

8. 編譯源碼，因為添加了介面，所以需要

   make update-api

   更新介面。然後再整編刷機。

9. service list 查看服務，不存在，這是因為selinux許可權沒加。

10. 添加sepolicy許可權

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. 重新編譯代碼，使用下麵測試代碼驗證

   import android.app.DemoManager;
   
   DemoManager om = (DemoManager) getSystemService(Context.DEMO_SERVICE);
   Log.d(TAG, "Current temperature is " + om.getCpuTemperature());

   最終log列印出100，服務添加完成。