HarmonyOS 鸿蒙Next ConnectivityKit中BLE低功耗蓝牙设备扫描设备ID会发生变化

HarmonyOS 鸿蒙Next ConnectivityKit中BLE低功耗蓝牙设备扫描设备ID会发生变化
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背景

最近研发一款养老项目，发现一个问题，使用ConnectivityKit中 BLE 低功耗蓝牙模块扫描设备时，获取到设备 DeviceID 在不同时间段会发生变化，造成无法判别设备唯一性问题

    let scanOptions: ble.ScanOptions = {
      interval: 500,
      dutyMode: ble.ScanDuty.SCAN_MODE_LOW_POWER,
      matchMode: ble.MatchMode.MATCH_MODE_AGGRESSIVE,
    }
    ble.startBLEScan(null, scanOptions);
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解决

方案 1

通过设备广播截取 扫描设备的时候可以获取设备的广播数据，设备的 mac地址一般包含在特定位置，代码如下：

  /**
   * 通过广播数据获取血糖设备mac
   * [@param](/user/param) data
   * [@returns](/user/returns) FF-FF-11-57-B6-5B
   */
  getMac(data: ArrayBuffer) {
    //  1. Uint8Array处理二进制(高效)
    const arr = new Uint8Array(data).slice(6, 12)
    let mac = ''
    // 2. 转换 16 进制
    arr.forEach((item, i) => {
      mac += i === 0 ? '' : '-'
      mac += item.toString(16)
        .padStart(2, '0')
        .toUpperCase()
    })
    return mac
  }
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注意：大部分设备适用

方案 2

通过给设备名称添加标识 falg 方式匹配，核心代码如下：

      const validDevices = devices.filter(dv => {
        if (scanFilter.type === 'mac') {
          let flag: boolean
          if (!scanFilter.door) {
            // 广播匹配
            flag = this.getMac(dv.data) === scanFilter.value
          } else {
            // 名称 falg匹配
            flag = this.isMatchDoor(scanFilter.value, dv.deviceName)
          }
          return list.some(item => item.deviceId === dv.deviceId) === false && flag
        } else {
          return list.some(item => item.deviceId === dv.deviceId) === false &&
          dv.deviceName.startsWith(scanFilter.value)
        }
      })
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这样就可以解决 DeviceID 变化问题，从而确定设备唯一性，保障后续设备的连接和控制操作正常进行。

最后贴下扫描完整代码：

  /**
   * 扫描蓝牙设备
   * [@param](/user/param) scanFilter
   * [@param](/user/param) callback
   */
  scanDevice(scanFilter: ScanFilter, callback: ScanCallback) {
    if (this.timer) {
      clearTimeout(this.timer)
    }
    // 1. 监听扫描结果
    let list: ble.ScanResult[] = []
    ble.on("BLEDeviceFind", (devices: ble.ScanResult[]) => {
      // 打印扫到设备
      devices.forEach(item => {
        Log.warn(`扫描中...\n ${item.deviceName || '--'} ${item.deviceId}`)
      })
      // const validDevices = devices.filter(dv => {
      //   return list.some(item => item.deviceId === dv.deviceId) === false
      // })
      const validDevices = devices.filter(dv => {
        if (scanFilter.type === 'mac') {
          let flag: boolean
          if (!scanFilter.door) {
            // 血糖匹配
            flag = this.getMac(dv.data) === scanFilter.value
          } else {
            // 门禁匹配
            flag = this.isMatchDoor(scanFilter.value, dv.deviceName)
          }
          return list.some(item => item.deviceId === dv.deviceId) === false && flag
        } else {
          return list.some(item => item.deviceId === dv.deviceId) === false &&
          dv.deviceName.startsWith(scanFilter.value)
        }
      })
      if (validDevices.length > 0) {
        list.push(...validDevices)
        // 精确匹配到后直接结束扫描
        if (scanFilter.type === 'mac') {
          callback(list)
          clearTimeout(this.timer)
          ble.off('BLEDeviceFind')
          ble.stopBLEScan()
        }
      }
    });
    //  2. 开启扫描
    let scanOptions: ble.ScanOptions = {
      interval: 500,
      dutyMode: ble.ScanDuty.SCAN_MODE_LOW_POWER,
      matchMode: ble.MatchMode.MATCH_MODE_AGGRESSIVE,
    }
    ble.startBLEScan(null, scanOptions);
// 3. 开启定时器控制时长
</span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">this</span></span></span><span class="hljs-function">.</span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">timer</span></span></span><span class="hljs-function"> = </span><span class="hljs-title"><span class="hljs-function"><span class="hljs-title">setTimeout</span></span></span><span class="hljs-params"><span class="hljs-function"><span class="hljs-params">(() =&gt; {
  callback(list)
  ble.</span></span><span class="hljs-literal"><span class="hljs-function"><span class="hljs-params"><span class="hljs-literal">off</span></span></span></span><span class="hljs-function"><span class="hljs-params">(</span></span><span class="hljs-string"><span class="hljs-function"><span class="hljs-params"><span class="hljs-string">'BLEDeviceFind'</span></span></span></span><span class="hljs-function"><span class="hljs-params">)
  ble.stopBLEScan()
}, </span></span><span class="hljs-number"><span class="hljs-function"><span class="hljs-params"><span class="hljs-number">10000</span></span></span></span><span class="hljs-function"><span class="hljs-params">)</span></span></span><span class="hljs-function">
}
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