Android通过编译源代码提供系统服务-android学习之旅（85）

最新推荐文章于 2023-09-12 23:41:02 发布

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原文链接：http://www.cnblogs.com/fengsehng/p/6048522.html

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#移动开发 #shell

本文详细介绍了如何通过编译 Android 4.1.2 的源代码，实现 FregServer 系统服务和 FregClient 服务代理。主要分为 client、common 和 server 三个部分，通过定义接口和公共方法，实现了客户端获取服务、设置和读取值的功能。同时，提供了 FregServer 服务的实现，包括启动线程池和处理通信请求的过程。最终，将服务文件拷贝至手机并运行客户端进行验证。

通过编译android4.1.2的源代码，添加一个FregServer的系统服务，以及一个服务代理FregClient

具体分为三部分，client，common，server，common中规定了client和common的接口，和一些公共方法

client部分代码

#define LOG_TAG "FregTest"

#include <utils/Log.h>
#include <binder/IServiceManager.h>

#include "../common/IFregService.h"

int main()
{
    IServiceManager = defaultServiceManager();
    sp<IBinder> binder = defaultServiceManager()->getService(String16(FREG_SERVICE));       //通过servicemanager获取名为xxx的Service的BpBinder代理对象
    if(binder == NULL) {
        ALOGE("[C] Failed to get freg service: %s.\n", FREG_SERVICE);
        return -1;
    }
    ALOGE("[C] Got BpBinder");
    sp<IFregService> service = IFregService::asInterface(binder);                           //将bpbinder代理对象封装为bpfregservice对象
    if(service == NULL) {
        ALOGE("[C] Failed to get freg service interface.\n");
        return -2;
    }
    ALOGE("[C] Got BpFregService");
    ALOGE("[C] Reading original value from FregService.\n");

    int32_t val = service->getVal();
    ALOGE("[C] Result: %d.\n", val);        

sleep(15);

    ALOGE("[C] Add value 1 to FregService.\n");
    val += 1;
    service->setVal(val);

    ALOGE("[C] Reading the value from FregService again:\n");

    val = service->getVal();
        ALOGE("[C] Result: %d.\n", val); 

    return 0;
}

mk文件

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional

LOCAL_SRC_FILES := ../common/IFregService.cpp \
    FregClient.cpp

LOCAL_SHARED_LIBRARIES:= libcutils libutils libbinder

LOCAL_MODULE := FregClient

include $(BUILD_EXECUTABLE)

Server部分

#define LOG_TAG "FregTest"

#include <stdlib.h>
#include <fcntl.h>

#include <utils/Log.h>
#include <binder/IServiceManager.h>
#include <binder/IPCThreadState.h>

#include "../common/IFregService.h"

#define FREG_DEVICE_NAME "/dev/freg"

class FregService : public BnFregService
{
public:
    FregService()
    {
        val = 0;
        ALOGE("[S] Tread: %d. In FregService().", gettid());
    }

    virtual ~FregService()
    {
        ALOGE("[S] Tread: %d. In ~FregService().", gettid());
    }

public:
    static void instantiate()
    {
        defaultServiceManager()->addService(String16(FREG_SERVICE), new FregService());     //获取servicemanager并调用addService函数实现服务注册
        ALOGE("[S] Tread: %d. instantiate(), addService-%s", gettid(), FREG_SERVICE);
    }

    int32_t getVal()
    {
        ALOGE("[S] Tread: %d. In getVal(), val-%d returned.", gettid(), val);
        return val;
    }

    void setVal(int32_t v)
        {
                val = v;
        ALOGE("[S] Tread: %d. In setVal(), val-%d set.", gettid(), val);
        }

private:
    int val;
};

int main(int argc, char** argv)
{
    FregService::instantiate();     

    ProcessState::self()->startThreadPool();    //启动线程池
ALOGE("[S] Tread: %d. ProcessState::self()->startThreadPool() finished.", gettid());
    IPCThreadState::self()->joinThreadPool();   //将主线程加入线程池
ALOGE("[S] Tread: %d. IPCThreadState::self()->joinThreadPool(); finished.", gettid());

    return 0;
}

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional

LOCAL_SRC_FILES := ../common/IFregService.cpp \
    FregServer.cpp

LOCAL_SHARED_LIBRARIES:= libcutils libutils libbinder

LOCAL_MODULE := FregServer

include $(BUILD_EXECUTABLE)

common部分

#define LOG_TAG "IFregService"

#include <utils/Log.h>

#include "IFregService.h"

using namespace android;

enum 
{
    GET_VAL = IBinder::FIRST_CALL_TRANSACTION,
    SET_VAL
};

class BpFregService: public BpInterface<IFregService>       //通信请求的发送
{
public:
    BpFregService(const sp<IBinder>& impl) 
        : BpInterface<IFregService>(impl)
    {

    }

public:
    int32_t getVal()
    {
        Parcel data;
        data.writeInterfaceToken(IFregService::getInterfaceDescriptor());   //获取了Ifregservice的接口名，并调用了parcel.writeInterfaceToken函数写入了data中

        Parcel reply;
        remote()->transact(GET_VAL, data, &reply);      //remote获取bpbinder代理对象，通过transact函数来发送请求

        int32_t val = reply.readInt32();

        return val;
    }

    void setVal(int32_t val)
        {
                Parcel data;
                data.writeInterfaceToken(IFregService::getInterfaceDescriptor());
                data.writeInt32(val);

                Parcel reply;
                remote()->transact(SET_VAL, data, &reply);
        }

};

IMPLEMENT_META_INTERFACE(FregService, "hikame.IFregService");//见最下

status_t BnFregService::onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)        //通信数据的接收与处理
{
    switch(code)
    {
        case GET_VAL:
        {
            CHECK_INTERFACE(IFregService, data, reply);

            int32_t val = getVal();
            reply->writeInt32(val);

            return NO_ERROR;
        }
        case SET_VAL:
                {
                        CHECK_INTERFACE(IFregService, data, reply);

            int32_t val = data.readInt32();
            setVal(val);

                        return NO_ERROR;
                }
        default:
        {
            return BBinder::onTransact(code, data, reply, flags);
        }
    }
}
/*IFregService的具体实现
#define IMPLEMENT_META_INTERFACE(INTERFACE, NAME)                       \
    const android::String16 I##INTERFACE::descriptor(NAME);             \
    const android::String16&                                            \
    I##INTERFACE::getInterfaceDescriptor() const {                      \
    return I##INTERFACE::descriptor;                                    \
    }                                                                   \
    android::sp<I##INTERFACE> I##INTERFACE::asInterface(                \
    const android::sp<android::IBinder>& obj)                           \
{                                                                       \
    android::sp<I##INTERFACE> intr;                                     \
if (obj != NULL) {
                                                                        \
    intr = static_cast<I##INTERFACE*>(                                  \
    obj->queryLocalInterface(                                           \
    I##INTERFACE::descriptor).get());                                   \
if (intr == NULL) {
                                                                        \
    intr = new Bp##INTERFACE(obj);                                      \
}                                                                       \   
}                                                                       \
    return intr;                                                        \
}                                                                       \
    I##INTERFACE::I##INTERFACE() { }                                    \
    I##INTERFACE::~I##INTERFACE() { }                                   \
*/

#ifndef IFREGSERVICE_H_
#define IFREGSERVICE_H_

#include <utils/RefBase.h>
#include <binder/IInterface.h>
#include <binder/Parcel.h>

#define FREG_SERVICE "hikame.FregService"           //Service名称

using namespace android;                            //在各个头文件中namespace为android的代码部分都被使用了

class IFregService: public IInterface
{
public:
    /*
#define DECLARE_META_INTERFACE(INTERFACE)                               \
    static const android::String16 descriptor;                          \
    static android::sp<I##INTERFACE> asInterface(                       \
            const android::sp<android::IBinder>& obj);                  \
    virtual const android::String16& getInterfaceDescriptor() const;    \
    I##INTERFACE();                                                     \
    virtual ~I##INTERFACE();                                            \
    定义了构造函数和析构函数，descriptor是接口名，getInterfaceDescriptor是获取该接口名的函数
    ？？这个android::sp是什么？A：/include/utils/StrongPointer.h
    */
    DECLARE_META_INTERFACE(FregService);
    virtual int32_t getVal() = 0;
    virtual void setVal(int32_t val) = 0;
};

class BnFregService: public BnInterface<IFregService>
{
public:
    virtual status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags = 0);
};

#endif