Android4.4添加系统服务(aidl接口服务)

一、准备

编译好的Android4.4源码
用于添加系统服务，用于获取CPU的Core数量。
AndroidStudio工具
用于编写apk调用系统接口

二、添加系统服务

添加aidl接口
frameworks/base/core/java/android/app/ICpuInfoManager.aidl
```
package android.app;interface ICpuInfoManager
{int getCpuCore();
}
```

添加系统服务，实现aidl文件的接口
frameworks/base/services/java/com/android/server/CpuInfoManagerService.java

package com.android.server;
import android.app.ICpuInfoManager;
import android.content.Context;
import android.util.Slog;public class CpuInfoManagerService extends ICpuInfoManager.Stub {private Context mContext;public CpuInfoManagerService(Context context){mContext = context;Slog.d("CPUINFO","Construct");}   @Overridepublic int getCpuCore(){return 4;}
}

添加系统服务的Manager
frameworks/base/core/java/android/app/CpuInfoManager.java

package android.app;                                                                                                              import android.content.Context;
import android.os.RemoteException;
import android.util.Slog;public class CpuInfoManager {Context mContext;ICpuInfoManager mService;public CpuInfoManager(Context context,ICpuInfoManager service){mContext = context;mService = service;}   public int getCpuCore(){if(mService != null){try{return mService.getCpuCore();}catch(RemoteException e){Slog.e("CPUINFO","RemoteException " + e);}   }   return -1;}
}

将aidl文件添加至Android.mk参与编译
frameworks/base/Android.mk
```
LOCAL_SRC_FILES += \core/java/android/app/ICpuInfoManager.aidl \
```

添加Context中的Service常量
frameworks/base/core/java/android/content/Context.java

    /***  用于Service的注册、SystemServer中的开机启动以及上层应用的使用*/public static final String CPU_INFO_SERVICE = "cpuinfo";

将实现的服务注册到系统中去
frameworks/base/core/java/android/app/ContextImpl.java

        registerService(CONSUMER_IR_SERVICE, new ServiceFetcher() {public Object createService(ContextImpl ctx) {return new ConsumerIrManager(ctx);}});// add register cpuinfo serviceregisterService(CPU_INFO_SERVICE, new ServiceFetcher() {public Object createService(ContextImpl ctx) {IBinder iBinder = ServiceManager.getService(Context.CPU_INFO_SERVICE);return new CpuInfoManager(ctx, ICpuInfoManager.Stub.asInterface(iBinder));}});

将注册的服务设置成开机启动
frameworks/base/services/java/com/android/server/SystemServer.java

        try {display.systemReady(safeMode, onlyCore);} catch (Throwable e) {reportWtf("making Display Manager Service ready", e);}// add cpuinfo servicetry{ServiceManager.addService(Context.CPU_INFO_SERVICE, new CpuInfoManagerService(context));} catch(Throwable e){Slog.e("CPUINFO","Failed to start CpuInfoManagerService " + e);}

更新api接口并且编译源码
```
       make  update-apimake -j32
```
之后更新系统。

三、编写app调用

AndroidStudio中引入AOSP的jar包
此处导入out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/classes.jar即可。

编写app测试
调用部分代码：

       CpuInfoManager cm = (CpuInfoManager) getSystemService("cpuinfo"); // cpuinfo即Context.CPU_INFO_SERVICE, 不知道为什么，AndroidStudio引入frameworkjar包后，调不到。Log.d("CPUINFO", "getcpuinfo: " + cm.getCpuCore());

四、调试

查看服务是否启动
串口下输入
```
service list | grep cpuinfo
```
出现以下信息即为添加系统调用服务成功：
```
53      cpuinfo: [android.app.ICpuInfoManager]
```

logcat查看app是否调用成功
串口下输入

logcat -vthreadtime -s CPUINFO

出现以下打印(cpu core is 4)即为app调用成功：

--------- beginning of /dev/log/system
--------- beginning of /dev/log/main
01-01 08:00:04.433  1930  1930 D CPUINFO : Construct
05-18 15:03:26.770  4993  4993 D CPUINFO : cpu core is 4

五、参考

Android AOSP 添加系统服务【aidl接口服务】Java层