[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(); }
2. 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 } }
3. 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; } }
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. 注册系统服务 frameworks/base/core/java/android/app/SystemServiceRegistry.java registerService(Context.DEMO_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. 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); }
8. 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。
9. service list 查看服务，不存在，这是因为selinux权限没加。
10. 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
11. 重新编译代码，使用下面测试代码验证 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。