Android -- 使用Binder API实现一个简单服务

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原创最新推荐文章于 2026-08-05 00:49:41 发布 2.1k 阅读 AI 写同款· GEO 优化 ›

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Android -- 使用Binder API实现一个简单服务

在上一篇博客中，我们借助ServiceManager从源码的角度简要分析了一下Binder的使用机制；接下来，我们就可以按照ServiceManager的实现套路，实现一个自己的Binder服务。

先列出代码目录结构：

1、服务业务接口：/mybinder/extra/IMyService.cpp
/mybinder/extra/IMyService.h
2、Server组件接口:/mybinder/server/IMyServer.cpp

/mybinder/server/Android.mk
3、Client组件接口:/mybinder/client/IMyClient.cpp

/ mybinder/client/Android.mk

下面直接上源代码。

一、业务接口代码

IMyService.h:

#ifndef  _MY_SERVICE_
#define	_MY_SERVICE_

#include <binder/IInterface.h>
#include <binder/Parcel.h>
#include <utils/String8.h>
#include <utils/String16.h>

#define MY_SERVICE "coder.core.MyService"

using namespace android;

//定义业务函数接口,声明DECLARE_META_INTERFACE()宏模板函数
class IMyService : public IInterface
{
public:
DECLARE_META_INTERFACE(MyService);
public:
virtual void sendInt(int32_t val) = 0;
virtual String8 getString() = 0;
public:
//业务函数的标号，用以区分是调用哪个业务,值对应的就是onTransact()、transact()
//中的code参数,用在switch...case...判断中
enum{
SEND_INT = IBinder::FIRST_CALL_TRANSACTION,
GET_STRING
};
};

//定义Server组件
class BnMyService : public BnInterface<IMyService>
{
public:
virtual status_t onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags = 0);
};

#endif

IMyService.cpp:

#include <binder/IPCThreadState.h>
#include <binder/Parcel.h>
#include "IMyService.h"

class BpMyService : public BpInterface<IMyService>
{
public:
BpMyService(const sp<IBinder>& impl) : BpInterface<IMyService>(impl){}
public:
void sendInt(int32_t val){
Parcel data, reply;
data.writeInterfaceToken(IMyService::getInterfaceDescriptor());
data.writeInt32(val);

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

String8 getString(){
Parcel data, reply;
data.writeInterfaceToken(IMyService::getInterfaceDescriptor());

remote()->transact(GET_STRING, data, &reply);
String8 res = reply.readString8();
return res;
}
};

//实现IMPLEMENT_META_INTERFACE()宏模板函数
IMPLEMENT_META_INTERFACE(MyService, MY_SERVICE);

status_t BnMyService::onTransact(uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
switch(code){
case SEND_INT:
{
CHECK_INTERFACE(IMyService, data, reply);
int32_t val = data.readInt32();//去除传入的参数，调用服务类的函数
sendInt(val);

return NO_ERROR;
}
break;
case GET_STRING:
{
CHECK_INTERFACE(IMyService, data, reply);
String8 res = getString();//调用服务类的函数
reply->writeString8(res);//将结果存入reply,BpMyService端可以读出该结果

return NO_ERROR;
}
break;
default:
return BBinder::onTransact(code, data, reply, flags);
}
};

二、Server组件代码

MyServer.cpp:

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

#include "../extra/IMyService.h"

class MyService : public BnMyService
{
public:
MyService(){option = 0;}
virtual ~MyService(){}
public:
static void instance(){
defaultServiceManager()->addService(String16(MY_SERVICE), new MyService());
}

void sendInt(int32_t val)
{
option = val;
}

String8 getString()
{
if(option <= 0)
return String8("you may not set val, or the value you set is <= 0.");
else
return String8("you have set the option with the value > 0.");

return String8("this is default string value.");
}
private:
int32_t option;
};

int main(int argc, char** argv)
{
//注册MyService服务到系统中
MyService::instance();

//开启线程池，接收处理Client发送的进程间通信请求
ProcessState::self()->startThreadPool();
IPCThreadState::self()->joinThreadPool();

return 0;
}

Server组件编译的Android.mk文件:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGSS := optional
LOCAL_SRC_FILES := ../extra/IMyService.cpp \
					MyServer.cpp
LOCAL_SHARED_LIBRARIES := libcutils libutils libbinder
LOCAL_MODULE := MyService
include $(BUILD_EXECUTABLE)

三、Client组件代码

MyClient.cpp:

#include <binder/IServiceManager.h>
#include "../extra/IMyService.h"

int main()
{
sp<IBinder> binder = defaultServiceManager()->getService((String16(MY_SERVICE));
if(binder == NULL){
printf("Failed to get the MyService binder object.\n");
return -1;
}

sp<IMyService> service = IMyService::asInterface(binder);
if(service == NULL){
printf("Failed to get the MyService service.\n");
return -1;
}

String8 str1 = service->getString();
printf("we get string value: %s \n",str1.string());

service->sendInt(2);
String8 str2 = service->getString();
printf("we get string value: %s\n",str2.string());
}

Client组件编译的Android.mk文件:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGSS := optional
LOCAL_SRC_FILES := ../extra/IMyService.cpp \
					MyClient.cpp
LOCAL_SHARED_LIBRARIES := libcutils libutils libbinder
LOCAL_MODULE := MyClient
include $(BUILD_EXECUTABLE)

代码组织完成后，我们可以将工程目录放到源码的external/目录下，使用mmm命令将Server组件、Client组件编译成两个可执行文件来运行、验证。

我们需要先运行Server组件，再运行Client组件；平台上验证的效果如图所示：