# HiSysEvent Listening
## Overview
HiSysEvent supports listening for events across processes. You can register a listener to listen for concerned events on a real-time basis. For example, you can enable the battery module to listen for power consumption event for power usage analysis.
## Available APIs
**Table 1** HiSysEvent listener APIs
API
Description
int HiSysEventManager::AddEventListener(std::shared_ptr<HiSysEventSubscribeCallBackBase> listener, std::vector<struct ListenerRule>& rules)
Registers a listener for system events. You can listen for certain events by specifying rules.
## How to Develop
### **C++**
In this example, you'll be instructed to register a listener for all system events that belong to the **HIVIEWDFX** domain.
1. Develop the source code.
- Import the corresponding header file:
hisysevent\_manager.h
- Implement the callback API.
HiSysEventSubscribeCallBackBase::OnHandle\(const std::string& domain, const std::string& eventName, const int eventType, const std::string& eventDetail\)
- Register a callback object.
HiSysEventManager::AddEventListener\(std::shared\_ptr listener, std::vector& rules\)
```
// Register a listener for all system events that belong to the HIVIEWDFX domain.
#include "hisysevent_manager.h"
#include
namespace OHOS {
namespace HiviewDFX {
// Implement the API for registering a listener for callback objects.
void HiSysEventToolListener::OnHandle(const std::string& domain, const std::string& eventName,
const int eventType, const std::string& eventDetail)
{
std::cout << eventDetail << std::endl;
}
void HiSysEventToolListener::OnServiceDied()
{
std::cout << std::string("service disconnect, exit") << std::endl;
exit(0);
}
} // namespace HiviewDFX
} // namespace OHOS
// Register a listener for callback objects.
auto toolListener = std::make_shared();
struct ListenerRule rule;
rule.ruleType = 1; // 1: default type
rule.domain = "HIVIEWDFX";
std::vector sysRules;
sysRules.push_back(rule);
HiSysEventManager::AddEventListener(toolListener, sysRules);
```
2. Modify the **BUILD.gn** file.
In the **BUILD.gn** file, add the **libhisyseventmanager** library that depends on the** hisysevent\_native** component.
```
external_deps = [ "hisysevent_native:libhisyseventmanager", ]
```