HiSysEvent Listening

Overview

Introduction

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 events for power usage analysis.

Constraints

Before subscribing to system events, you need to configure HiSysEvent logging. For details, see HiSysEvent Logging Configuration.

Development Guidelines

Available APIs

Table 1 Description of HiSysEventListener APIs

Table 2 Description of ListenerRule

Table 3 Description of RuleType

Table 4 Description of HiSysEventListener

Table 5 Description of HiSysEventRecord

How to Develop

C++

The following provides an example of how to use C++ APIs of HiSysEvent.

1. Develop the source code. Import the DemoListener.h header file, which contains the DemoListener class for implementing the custom event callback.

   #ifndef DEMO_LISTENER_H
   #define DEMO_LISTENER_H
   
   #include "hisysevent_listener.h"
   
   #include <string>
   
   class DemoListener : public OHOS::HiviewDFX::HiSysEventListener {
   public:
       explicit DemoListener() : HiSysEventListener() {}
     virtual ~DemoListener() {}
   
   public:
       void OnEvent(std::shared_ptr<HiSysEventRecord> sysEvent);
       void OnServiceDied();
   };
   
   #endif // DEMO_LISTENER_H
   

   Create the DemoListener.cpp file, and add the implementation logic of the custom event callback API in the DemoListener class.

   #include "demo_listener.h"
   
   #include <iostream>
   
   void DemoListener::OnEvent(std::shared_ptr<HiSysEventRecord> sysEvent)
   {
       if (sysEvent == nullptr) {
           return;
       }
       std::cout << sysEvent.AsJson() << std::endl;
   }
   
   void DemoListener::OnServiceDied()
   {
       std::cout << std::string("service disconnect, exit") << std::endl;
       exit(0);
   }
   

   Call the AddEventListener API of the HiSysEventManager class to add a listener for system events.

   auto demoListener = std::make_shared<DemoListener>();
   // Add a ListenerRule object based on the event tag, with RuleType left unspecified (in this case, ruleType is defaulted to WHOLE_WORD).
   ListenerRule tagRule("dfx");
   // Add a ListenerRule object based on the event tag, with RuleType set as REGULAR.
   ListenerRule regRule("dfx.*", RuleType::REGULAR);
   // Add a ListenerRule object based on the event domain and event name, with RuleType set as PREFIX.
   ListenerRule domainNameRule("HIVIEWDFX", "APP_USAGE", RuleType::PREFIX);
   std::vector<ListenerRule> sysRules;
   sysRules.push_back(tagRule);
   sysRules.push_back(regRule);
   sysRules.push_back(domainNameRule);
   HiSysEventManager::AddEventListener(demoListener, sysRules);
   

2. Configure the BUILD.gn file. In the BUILD.gn file, add the libhisysevent and libhisyseventmanager libraries that depend on the hisysevent_native component.

   external_deps = [
     "hisysevent_native:libhisysevent",
     "hisysevent_native:libhisyseventmanager",
   ]