MessageBuilder Bluetooth Communication

First, let's review the Overall Architecture of the Zepp OS Mini Program.

Communication between "Device App" and "Side Service" is carried out via Bluetooth.

The "Device App" uses Bluetooth capabilities through the hmBle API and the "Side Service" uses Bluetooth capabilities through the Messaging API, both of which can currently only manipulate binary data and are cumbersome for developers to organize data structures.

Refer to the sample ToDoList, where /shared/message.js wraps hmBle and Messaging API to make it easier for developers to develop applications.

This article shares the experience of using MessageBuilder, i.e. message.js, to complete the communication between "Device App" and "Side Service"

Usage

1. Environmental Preparation

/shared/message.js relies on a lot of methods that the host environment does not have, so you need to polyfill the environment. All the files in the /shared directory will be used, and are imported in app.js

import './shared/device-polyfill'

2. Establish connection

Instantiate MessageBuilder in Device App and Side Service respectively, and perform Bluetooth channel connection establishment in their respective lifecycles.

caution

In the onDestroy lifecycle of "Device App", connection destruction is required to prevent memory leaks.

import './shared/device-polyfill'
import { MessageBuilder } from './shared/message'

// need to pass in the appId
const appId = 27280
const messageBuilder = new MessageBuilder({ appId })

App({
  globalData: {
    messageBuilder: messageBuilder,
  },
  onCreate(options) {
    console.log('app on create invoke')
    // establish connection
    messageBuilder.connect()
  },

  onDestroy(options) {
    console.log('app on destroy invoke')
    messageBuilder.disConnect()
  }
})

import { MessageBuilder } from '../shared/message'

const messageBuilder = new MessageBuilder()

AppSideService({
  onInit() {
    // establish connection
    messageBuilder.listen(() => {})
  },
})

3. Event-based communication

After the connection is established, subsequent communication is based on the event mechanism, with listening and dispatching methods on both ends, just refer to the code example.

const { messageBuilder } = getApp()._options.globalData
const logger = DeviceRuntimeCore.HmLogger.getLogger('demo')

Page({
  build() {
    // receive a message from the Side Service
    messageBuilder.on('call', ({ payload: buf }) => {
      // call the messageBuilder.buf2Json method to convert the buffer to a JS JSON object
      const data = messageBuilder.buf2Json(buf)
      logger.log('data', data)
    })

    // send a message to Side Service
    messageBuilder.request({
      method: 'GET',
      params: {
        index: 0
      }
    }).then(data => {
      // process Side Service responses
      const { result } = data
      logger.log(result)
    })
  }
})

import { MessageBuilder } from '../shared/message'

const messageBuilder = new MessageBuilder()

AppSideService({
  onInit() {
    messageBuilder.listen(() => {})

    // send a message to Device App
    messageBuilder.call({ text: 'Hello Zepp OS' })

    // receive a message from Device App
    messageBuilder.on('request', (ctx) => {
      const payload = messageBuilder.buf2Json(ctx.request.payload)
      const { method, params } = payload

      if (method === 'GET') {
        ctx.response({
          data: { result : 0 }
        })
      }
    })
  },
})