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 ble 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 example ToDoList, where /shared/message.js encapsulates the Bluetooth communication process, making 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"

tip

The communication library that Device Application relies on is /shared/message.js.

The communication library that the Side Service depends on is /shared/message-side.js.

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'
import { getPackageInfo } from '@zos/app'
import * as ble from '@zos/ble'

App({
  globalData: {
    messageBuilder: null
  },
  onCreate(options) {
    console.log('app on create invoke')
    // establish connection
    const { appId } = getPackageInfo()
    const messageBuilder = new MessageBuilder({ appId, appDevicePort: 20, appSidePort: 0, ble })
    this.globalData.messageBuilder = messageBuilder
    messageBuilder.connect()
  },
  onDestroy(options) {
    console.log('app on destroy invoke')
    messageBuilder.disConnect()
  }
})

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

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.

import { log } from '@zos/utils'

const { messageBuilder } = getApp()._options.globalData
const logger = log.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-side'

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 }
        })
      }
    })
  },
})