harmony 鸿蒙远端状态订阅开发实例
远端状态订阅开发实例
IPC/RPC提供对远端Stub对象状态的订阅机制,在远端Stub对象消亡时,可触发消亡通知告诉本地Proxy对象。这种状态通知订阅需要调用特定接口完成,当不再需要订阅时也需要调用特定接口取消。使用这种订阅机制的用户,需要实现消亡通知接口DeathRecipient并实现onRemoteDied方法清理资源。该方法会在远端Stub对象所在进程消亡或所在设备离开组网时被回调。值得注意的是,调用这些接口有一定的顺序。首先,需要Proxy订阅Stub消亡通知,若在订阅期间Stub状态正常,则在不再需要时取消订阅;若在订阅期间Stub所在进程退出或者所在设备退出组网,则会自动触发Proxy自定义的后续操作。
使用场景
这种订阅机制适用于本地Proxy对象需要感知远端Stub对象所在进程消亡,或所在设备离开组网的场景。当Proxy感知到Stub端消亡后,可适当清理本地资源。此外,RPC目前不提供匿名Stub对象的消亡通知,即只有向SAMgr注册过的服务才能被订阅消亡通知,IPC则支持匿名对象的消亡通知。
Native侧接口
接口名 | 返回值类型 | 功能描述 |
---|---|---|
AddDeathRecipient(const sptr<DeathRecipient> &recipient); | bool | 订阅远端Stub对象状态。 |
RemoveDeathRecipient(const sptr<DeathRecipient> &recipient); | bool | 取消订阅远端Stub对象状态。 |
OnRemoteDied(const wptr<IRemoteObject> &object); | void | 当远端Stub对象死亡时回调。 |
参考代码
#include "iremote_broker.h"
#include "iremote_stub.h"
//定义消息码
enum {
TRANS_ID_PING_ABILITY = 5,
TRANS_ID_REVERSED_MONITOR
};
const std::string DESCRIPTOR = "test.ITestAbility";
class ITestService : 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
};
class TestServiceProxy : public IRemoteProxy<ITestAbility> {
public:
explicit TestAbilityProxy(const sptr<IRemoteObject> &impl);
virtual int TestPingAbility(const std::u16string &dummy) override;
int TestAnonymousStub();
private:
static inline BrokerDelegator<TestAbilityProxy> delegator_; // 方便后续使用iface_cast宏
};
TestServiceProxy::TestServiceProxy(const sptr<IRemoteObject> &impl)
: IRemoteProxy<ITestAbility>(impl)
{
}
int TestServiceProxy::TestPingAbility(const std::u16string &dummy){
MessageOption option;
MessageParcel dataParcel, replyParcel;
dataParcel.WriteString16(dummy);
int error = PeerHolder::Remote()->SendRequest(TRANS_ID_PING_ABILITY, dataParcel, replyParcel, option);
int result = (error == ERR_NONE) ? replyParcel.ReadInt32() : -1;
return result;
}
#include "iremote_object.h"
class TestDeathRecipient : public IRemoteObject::DeathRecipient {
public:
virtual void OnRemoteDied(const wptr<IRemoteObject>& remoteObject);
}
void TestDeathRecipient::OnRemoteDied(const wptr<IRemoteObject>& remoteObject)
{
}
sptr<IPCObjectProxy> object = new IPCObjectProxy(1, to_utf16(DESCRIPTOR));
sptr<IRemoteObject::DeathRecipient> deathRecipient (new TestDeathRecipient()); // 构造一个消亡通知对象
bool result = object->AddDeathRecipient(deathRecipient); // 注册消亡通知
result = object->RemoveDeathRecipient(deathRecipient); // 移除消亡通知
JS侧接口
接口名 | 返回值类型 | 功能描述 |
---|---|---|
registerDeathRecipient | void | 注册用于接收远程对象消亡通知的回调,增加 proxy 对象上的消亡通知。 |
unregisterDeathRecipient | void | 注销用于接收远程对象消亡通知的回调。 |
onRemoteDied | void | 在成功添加死亡通知订阅后,当远端对象死亡时,将自动调用本方法。 |
获取context
Stage模型在连接服务前需要先获取context
import UIAbility from '@ohos.app.ability.UIAbility';
import Want from '@ohos.app.ability.Want';
import AbilityConstant from '@ohos.app.ability.AbilityConstant';
import window from '@ohos.window';
export default class MainAbility extends UIAbility {
onCreate(want: Want, launchParam: AbilityConstant.LaunchParam) {
console.log("[Demo] MainAbility onCreate");
let context = this.context;
}
onDestroy() {
console.log("[Demo] MainAbility onDestroy");
}
onWindowStageCreate(windowStage: window.WindowStage) {
// Main window is created, set main page for this ability
console.log("[Demo] MainAbility onWindowStageCreate");
}
onWindowStageDestroy() {
// Main window is destroyed, release UI related resources
console.log("[Demo] MainAbility onWindowStageDestroy");
}
onForeground() {
// Ability has brought to foreground
console.log("[Demo] MainAbility onForeground");
}
onBackground() {
// Ability has back to background
console.log("[Demo] MainAbility onBackground");
}
}
参考代码
// 仅FA模型需要导入@ohos.ability.featureAbility
// import FA from "@ohos.ability.featureAbility";
import Want from '@ohos.app.ability.Want';
import common from '@ohos.app.ability.common';
import rpc from '@ohos.rpc';
let proxy: rpc.IRemoteObject|undefined = undefined;
let connect: common.ConnectOptions = {
onConnect: (elementName, remoteProxy) => {
console.log("RpcClient: js onConnect called.");
proxy = remoteProxy;
},
onDisconnect: (elementName) => {
console.log("RpcClient: onDisconnect");
},
onFailed: () => {
console.log("RpcClient: onFailed");
}
};
let want: Want = {
bundleName: "com.ohos.server",
abilityName: "com.ohos.server.EntryAbility",
};
// FA模型通过此方法连接服务
// FA.connectAbility(want, connect);
this.context.connectServiceExtensionAbility(want, connect);
上述onConnect回调函数中的proxy对象需要等ability异步连接成功后才会被赋值,然后才可调用proxy对象的unregisterDeathRecipient接口方法注销死亡回调
import Want from '@ohos.app.ability.Want';
import common from '@ohos.app.ability.common';
import rpc from '@ohos.rpc';
class MyDeathRecipient implements rpc.DeathRecipient{
onRemoteDied() {
console.log("server died");
}
}
let deathRecipient = new MyDeathRecipient();
let proxy: rpc.IRemoteObject|undefined = undefined;
proxy.registerDeathRecipient(deathRecipient, 0);
proxy.unregisterDeathRecipient(deathRecipient, 0);
Stub感知Proxy消亡(匿名Stub的使用)
正向的消亡通知是Proxy感知Stub的状态,若想达到反向的死消亡通知,即Stub感知Proxy的状态,可以巧妙的利用正向消亡通知。如两个进程A(原Stub所在进程)和B(原Proxy所在进程),进程B在获取到进程A的Proxy对象后,在B进程新建一个匿名Stub对象(匿名指未向SAMgr注册),可称之为回调Stub,再通过SendRequest接口将回调Stub传给进程A的原Stub。这样一来,进程A便获取到了进程B的回调Proxy。当进程B消亡或B所在设备离开组网时,回调Stub会消亡,回调Proxy会感知,进而通知给原Stub,便实现了反向消亡通知。
注意:
反向死亡通知仅限设备内跨进程通信使用,不可用于跨设备。
当匿名Stub对象没有被任何一个Proxy指向的时候,内核会自动回收。
参考代码
// Proxy
int TestAbilityProxy::TestAnonymousStub()
{
MessageOption option;
MessageParcel dataParcel, replyParcel;
dataParcel.UpdateDataVersion(Remote());
dataParcel.WriteRemoteObject(new TestAbilityStub());
int error = Remote()->SendRequest(TRANS_ID_REVERSED_MONITOR,dataParcel, replyParcel, option);
int result = (error == ERR_NONE) ? replyParcel.ReadInt32() : -1;
return result;
}
// Stub
int TestAbilityStub::OnRemoteRequest(uint32_t code, MessageParcel &data, MessageParcel &reply, MessageOption &option)
{
switch (code) {
case TRANS_ID_REVERSED_MONITOR: {
sptr<IRemoteObject> obj = data.ReadRemoteObject();
if (obj == nullptr) {
reply.WriteInt32(ERR_NULL_OBJECT);
return ERR_NULL_OBJECT;
}
bool result = obj->AddDeathRecipient(new TestDeathRecipient());
result ? reply.WriteInt32(ERR_NONE) : reply.WriteInt32(-1);
break;
}
default:
break;
}
return ERR_NONE;
}
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