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IPC与RPC通信开发指导

IPC与RPC通信开发指导

场景介绍

IPC/RPC的主要工作是让运行在不同进程的Proxy和Stub互相通信，包括Proxy和Stub运行在不同设备的情况。

接口说明

表1 Native侧IPC接口

类/接口 方法 功能说明
IRemoteBroker sptr<IRemoteObject> AsObject() 返回通信对象。Stub端返回RemoteObject对象本身，Proxy端返回代理对象。
IRemoteStub virtual int OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply, MessageOption &option) 请求处理方法，派生类需要重写该方法用来处理Proxy的请求并返回结果。
IRemoteProxy 业务的Pory类需要从IRemoteProxy类派生。

开发步骤

Native侧开发步骤

  1. 添加依赖

    SDK依赖：

    #ipc场景
external_deps = [
  "ipc:ipc_single",
]

#rpc场景
external_deps = [
  "ipc:ipc_core",
]
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    此外， IPC/RPC依赖的refbase实现在公共基础库下，请增加对utils的依赖：

    external_deps = [
  "c_utils:utils",
]
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  2. 定义IPC接口ITestAbility

    SA接口继承IPC基类接口IRemoteBroker，接口里定义描述符、业务函数和消息码，其中业务函数在Proxy端和Stub端都需要实现。

    #include "iremote_broker.h"

//定义消息码
const int TRANS_ID_PING_ABILITY = 5

const std::string DESCRIPTOR = "test.ITestAbility";

class ITestAbility : public IRemoteBroker {
public:
    // DECLARE_INTERFACE_DESCRIPTOR是必需的，入参需使用std::u16string；
    DECLARE_INTERFACE_DESCRIPTOR(to_utf16(DESCRIPTOR));
    virtual int TestPingAbility(const std::u16string &dummy) = 0; // 定义业务函数
};
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  3. 定义和实现服务端TestAbilityStub

    该类是和IPC框架相关的实现，需要继承 IRemoteStub<ITestAbility>。Stub端作为接收请求的一端，需重写OnRemoteRequest方法用于接收客户端调用。

    #include "iability_test.h"
#include "iremote_stub.h"

class TestAbilityStub : public IRemoteStub<ITestAbility> {
public:
    virtual int OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply, MessageOption &option) override;
    int TestPingAbility(const std::u16string &dummy) override;
 };

int TestAbilityStub::OnRemoteRequest(uint32_t code,
    MessageParcel &data, MessageParcel &reply, MessageOption &option)
{
    switch (code) {
        case TRANS_ID_PING_ABILITY: {
            std::u16string dummy = data.ReadString16();
            int result = TestPingAbility(dummy);
            reply.WriteInt32(result);
            return 0;
        }
        default:
            return IPCObjectStub::OnRemoteRequest(code, data, reply, option);
    }
}
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  4. 定义服务端业务函数具体实现类TestAbility

    #include "iability_server_test.h"

class TestAbility : public TestAbilityStub {
public:
    int TestPingAbility(const std::u16string &dummy);
}

int TestAbility::TestPingAbility(const std::u16string &dummy) {
    return 0;
}
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  5. 定义和实现客户端 TestAbilityProxy

    该类是Proxy端实现，继承IRemoteProxy<ITestAbility>，调用SendRequest接口向Stub端发送请求，对外暴露服务端提供的能力。

    #include "iability_test.h"
#include "iremote_proxy.h"
#include "iremote_object.h"

class TestAbilityProxy : public IRemoteProxy<ITestAbility> {
public:
    explicit TestAbilityProxy(const sptr<IRemoteObject> &impl);
    int TestPingAbility(const std::u16string &dummy) override;
private:
    static inline BrokerDelegator<TestAbilityProxy> delegator_; // 方便后续使用iface_cast宏
}

TestAbilityProxy::TestAbilityProxy(const sptr<IRemoteObject> &impl)
    : IRemoteProxy<ITestAbility>(impl)
{
}

int TestAbilityProxy::TestPingAbility(const std::u16string &dummy){
    MessageOption option;
    MessageParcel dataParcel, replyParcel;
    dataParcel.WriteString16(dummy);
    int error = Remote()->SendRequest(TRANS_ID_PING_ABILITY, dataParcel, replyParcel, option);
    int result = (error == ERR_NONE) ? replyParcel.ReadInt32() : -1;
    return result;
}
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  6. SA注册与启动

    SA需要将自己的TestAbilityStub实例通过AddSystemAbility接口注册到SystemAbilityManager，设备内与分布式的注册参数不同。

    // 注册到本设备内
auto samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
samgr->AddSystemAbility(saId, new TestAbility());

// 在组网场景下，会被同步到其他设备上
auto samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
ISystemAbilityManager::SAExtraProp saExtra;
saExtra.isDistributed = true; // 设置为分布式SA
int result = samgr->AddSystemAbility(saId, new TestAbility(), saExtra);
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  7. SA获取与调用

    通过SystemAbilityManager的GetSystemAbility方法可获取到对应SA的代理IRemoteObject，然后构造TestAbilityProxy即可。

    // 获取本设备内注册的SA的proxy
sptr<ISystemAbilityManager> samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();
sptr<IRemoteObject> remoteObject = samgr->GetSystemAbility(saId);
sptr<ITestAbility> testAbility = iface_cast<ITestAbility>(remoteObject); // 使用iface_cast宏转换成具体类型

// 获取其他设备注册的SA的proxy
sptr<ISystemAbilityManager> samgr = SystemAbilityManagerClient::GetInstance().GetSystemAbilityManager();

// networkId是组网场景下对应设备的标识符，可以通过GetLocalNodeDeviceInfo获取
sptr<IRemoteObject> remoteObject = samgr->GetSystemAbility(saId, networkId);
sptr<TestAbilityProxy> proxy(new TestAbilityProxy(remoteObject)); // 直接构造具体Proxy
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JS侧开发步骤

  1. 添加依赖

    import rpc from "@ohos.rpc"
import featureAbility from "@ohos.ability.featureAbility"
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  2. 绑定Ability

    首先，构造变量want，指定要绑定的Ability所在应用的包名、组件名，如果是跨设备的场景，还需要绑定目标设备NetworkId（组网场景下对应设备的标识符，可以使用deviceManager获取目标设备的NetworkId）；然后，构造变量connect，指定绑定成功、绑定失败、断开连接时的回调函数；最后，使用featureAbility提供的接口绑定Ability。

    import rpc from "@ohos.rpc"
import featureAbility from "@ohos.ability.featureAbility"

let proxy = null
let connectId = null

// 单个设备绑定Ability
let want = {
    // 包名和组件名写实际的值
    "bundleName": "ohos.rpc.test.server",
    "abilityName": "ohos.rpc.test.server.ServiceAbility",
}
let connect = {
    onConnect:function(elementName, remote) {
        proxy = remote
    },
    onDisconnect:function(elementName) {
    },
    onFailed:function() {
        proxy = null
    }
}
connectId = featureAbility.connectAbility(want, connect)

// 如果是跨设备绑定，可以使用deviceManager获取目标设备NetworkId
import deviceManager from '@ohos.distributedHardware.deviceManager'
function deviceManagerCallback(deviceManager) {
    let deviceList = deviceManager.getTrustedDeviceListSync()
    let networkId = deviceList[0].networkId
    let want = {
        "bundleName": "ohos.rpc.test.server",
        "abilityName": "ohos.rpc.test.service.ServiceAbility",
        "networkId": networkId,
        "flags": 256
    }
    connectId = featureAbility.connectAbility(want, connect)
}
// 第一个参数是本应用的包名，第二个参数是接收deviceManager的回调函数
deviceManager.createDeviceManager("ohos.rpc.test", deviceManagerCallback)
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  3. 服务端处理客户端请求

    服务端被绑定的Ability在onConnect方法里返回继承自rpc.RemoteObject的对象，该对象需要实现onRemoteMessageRequest方法，处理客户端的请求。

    onConnect(want: Want) {
    var robj:rpc.RemoteObject = new Stub("rpcTestAbility")
    return robj
}
class Stub extends rpc.RemoteObject {
    constructor(descriptor) {
        super(descriptor)
    }
    onRemoteMessageRequest(code, data, reply, option) {
        // 根据code处理客户端的请求
        return true
    }
}
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  4. 客户端处理服务端响应

    客户端在onConnect回调里接收到代理对象，调用sendRequestAsync方法发起请求，在期约（JavaScript期约：用于表示一个异步操作的最终完成或失败及其结果值）或者回调函数里接收结果。

    // 使用期约
let option = new rpc.MessageOption()
let data = rpc.MessageParcel.create()
let reply = rpc.MessageParcel.create()
// 往data里写入参数
proxy.sendRequestAsync(1, data, reply, option)
    .then(function(result) {
        if (result.errCode != 0) {
            console.error("send request failed, errCode: " + result.errCode)
            return
        }
        // 从result.reply里读取结果
    })
    .catch(function(e) {
        console.error("send request got exception: " + e)
    }
    .finally(() => {
        data.reclaim()
        reply.reclaim()
    })

// 使用回调函数
function sendRequestCallback(result) {
    try {
        if (result.errCode != 0) {
            console.error("send request failed, errCode: " + result.errCode)
            return
        }
        // 从result.reply里读取结果
    } finally {
        result.data.reclaim()
        result.reply.reclaim()
    }
}
let option = new rpc.MessageOption()
let data = rpc.MessageParcel.create()
let reply = rpc.MessageParcel.create()
// 往data里写入参数
proxy.sendRequest(1, data, reply, option, sendRequestCallback)
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  5. 断开连接

    IPC通信结束后，使用featureAbility的接口断开连接。

    import rpc from "@ohos.rpc"
import featureAbility from "@ohos.ability.featureAbility"
function disconnectCallback() {
    console.info("disconnect ability done")
}
featureAbility.disconnectAbility(connectId, disconnectCallback)
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