[移动开发]Android4.4添加系统服务(aidl接口服务)

一、 准备

1. 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。
2. AndroidStudio工具
   用于编写apk调用系统接口

二、 添加系统服务

1. 添加aidl接口
   frameworks/base/core/java/android/app/ICpuInfoManager.aidl

package android.app;

interface ICpuInfoManager
{
    int getCpuCore();
}

2. 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");
        }   

        @Override
        public int getCpuCore(){
                return 4;
        }   
}

3. 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;
        }   
}

4. 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 \

5. .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";

6. 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 service
        registerService(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));
            }});

7. 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 service
        try{
            ServiceManager.addService(Context.CPU_INFO_SERVICE, new CpuInfoManagerService(context));
        } catch(Throwable e){
            Slog.e("CPUINFO","Failed to start CpuInfoManagerService " + e);
        }

8. 更新api接口并且编译源码

       make  update-api
       make -j32

之后更新系统。

三、编写app调用

1. AndroidStudio中引入AOSP的jar包
   此处导入out/target/common/obj/JAVA_LIBRARIES/framework_intermediates/classes.jar即可。
2. 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

1. 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]

2. 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

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