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。派生类需要实现,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,处理Proxy的请求并返回结果。 |
IRemoteProxy | 业务Proxy类派生自IRemoteProxy类。 |
开发步骤
Native侧开发步骤
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。
class ITestAbility : public IRemoteBroker {
public:
// DECLARE_INTERFACE_DESCRIPTOR是必须的,入参需使用std::u16string;
DECLARE_INTERFACE_DESCRIPTOR(u"test.ITestAbility");
int TRANS_ID_PING_ABILITY = 1; // 定义消息码
virtual int TestPingAbility(const std::u16string &dummy) = 0; // 定义业务函数
};
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。
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 TestServiceStub::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);
}
}
定义服务端业务函数具体实现类TestAbility
class TestAbility : public TestAbilityStub {
public:
int TestPingAbility(const std::u16string &dummy);
}
int TestAbility::TestPingAbility(const std::u16string &dummy) {
return 0;
}
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。
class TestAbilityProxy : public IRemoteProxy<ITestAbility> {
public:
explicit TestAbilityProxy(const sptr<IRemoteObject> &impl);
int TestPingService(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::TestPingService(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;
}
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);
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();
sptr<IRemoteObject> remoteObject = samgr->GetSystemAbility(sdid, deviceId); // deviceId是指定设备的标识符
sptr<TestAbilityProxy> proxy(new TestAbilityProxy(remoteObject)); // 直接构造具体Proxy