Using Emitter for Inter-Thread Communication

Emitter provides APIs for sending and processing events between threads, including the APIs for processing events that are subscribed to in persistent or one-shot manner, unsubscribing from events, and emitting events to the event queue.

To develop the Emitter mode, perform the following steps:

1. Subscribe to an event.

   import emitter from "@ohos.events.emitter";
   
   // Define an event with eventId 1.
   let event = {
     eventId: 1
   };
   
   // Trigger the callback after the event with eventId 1 is received.
   let callback = (eventData) => {
     console.info('event callback');
   };
   
   // Subscribe to the event with eventId 1.
   emitter.on(event, callback);
   

2. Emit the event.

   import emitter from "@ohos.events.emitter";
   
   // Define an event with eventId 1 and priority Low.
   let event = {
     eventId: 1,
     priority: emitter.EventPriority.LOW
   };
   
   let eventData = {
     data: {
       "content": "c",
       "id": 1,
       "isEmpty": false,
     }
   };
   
   // Emit the event with eventId 1 and event content eventData.
   emitter.emit(event, eventData);