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[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。

添加接口

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

package android.app;

interface IDemoManager
{
    int getCpuTemperature();
}

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
    }
}

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;
    }
}

添加aidl到Makefile src

frameworks/base/Android.mk

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

添加DEMO_SERVICE常量

frameworks/base/core/java/android/content/Context.java
```
public static final String DEMO_SERVICE = "demo";
```

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));
}});

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);
}

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。
service list 查看服务，不存在，这是因为selinux权限没加。

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

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。

原文 http://wossoneri.github.io/2018/09/15/[Android][Framework]create-system-service/

正文到此结束