#星光不负 码向未来# 从前端到鸿蒙：一次“分布式签到”的落地复盘 原创 精华

// SignInPage.ets
@Entry
@Component
struct SignInPage {
  @State userId: string = ''
  @State status: string = '未签到'
  @State count: number = 0

  build() {
    Column({ space: 12 }) {
      Text(`状态：${this.status}`).fontSize(20).fontWeight(FontWeight.Medium)
      TextInput({ placeholder: '输入/扫描 用户ID' })
        .onChange(v => this.userId = v)
      Row({ space: 12 }) {
        Button('本机签到').onClick(async () => await this.signLocal())
        Button('近场同步').onClick(async () => await this.syncNearby())
      }
      Text(`已签到人数：${this.count}`).fontSize(16)
    }.padding(24)
  }

  async signLocal() {
    if (!this.userId) { this.status = '请输入用户ID'; return }
    // 写入本地 + 分布式（见下文 4.2、4.3）
    const ok = await putAttendance(this.userId)
    this.status = ok ? '签到成功' : '重复或失败'
    this.count = await getAttendanceCount()
  }

  async syncNearby() {
    // 触发近场同步（见下文 4.3）
    const synced = await syncAttendanceNearby()
    this.status = synced ? '近场同步完成' : '暂无可同步设备'
  }
}

// storage/kv.ts
// 说明：采用分布式 KV/对象存储时，需设置 autoSync/securityLevel，接口名以实际 SDK 为准
import kv from '@ohos.data.distributedKVStore'  // 示例命名，以实际为准

let store: any

export async function initStore() {
  const kvManager = await kv.createKVManager({ bundleName: 'com.example.signin' })
  store = await kvManager.getKVStore('attendance', {
    createIfMissing: true, backup: true, encrypt: false, autoSync: true // 自动与可信设备同步
  })
}

export async function putAttendance(uid: string) {
  const key = `uid:${uid}`
  const exists = await store.get(key).catch(() => undefined)
  if (exists) return false
  await store.put(key, JSON.stringify({ uid, ts: Date.now(), device: await currentDeviceId() }))
  return true
}

export async function getAttendanceCount(): Promise<number> {
  const keys = await store.getKeys('uid:')
  return keys?.length ?? 0
}

// nearby/sync.ts
import deviceManager from '@ohos.distributedHardware.deviceManager' // 示例
import { pullDiffAndMerge } from './reconcile'

let dm: any

export async function initNearby() {
  dm = await deviceManager.createDeviceManager('com.example.signin')
  dm.on('deviceStateChange', (action, device) => {
    // onFound/onLost，可提示 UI 或触发自动同步
  })
}

export async function syncAttendanceNearby(): Promise<boolean> {
  const list = dm.getTrustedDeviceListSync() || []
  if (!list.length) return false
  // 点对点：按 deviceId 拉取对方缺失的记录并合并
  for (const d of list) {
    await pullDiffAndMerge(d.deviceId) // 内部通过分布式对象或软总线信道传输增量
  }
  return true
}

{
  "module": {
    "abilities": [{
      "name": "EntryAbility",
      "skills": [{
        "actions": ["action.view"],
        "uris": [{
          "scheme": "https",
          "host": "events.你的网站哈.com",
          "paths": ["/signin/*"]
        }]
      }]
    }]
  }
}

// EntryAbility.ets
import { initStore } from './storage/kv'
import { warmAvatarCache, warmDictionary } from './prefetch'
import { initNearby } from './nearby/sync'

export default class EntryAbility {
  async onCreate() {
    // 注意：预加载应控制体积与耗时，避免阻塞 UI 线程
    initStore()                 // 建立 KV 连接
    warmDictionary()            // 预热姓名索引、班级映射等
    warmAvatarCache()           // 头像小图缓存（弱网下也能即时展示）
    initNearby()                // 准备近场发现
  }
}

// apm/trace.ts
import agconnect from '@hw-agconnect/core'     // 示例
import apms from '@hw-agconnect/apms'          // 示例

export async function initAPM() {
  await agconnect.instance().config({ /* 项目参数 */ })
  apms.instance().enable() // 打开应用性能监控
}

export function traceColdStart<T>(task: () => Promise<T>) {
  const t = apms.instance().newTrace('cold_start')
  t.start()
  return task().finally(() => t.stop())
}

export function metric(name: string, value: number) {
  apms.instance().setCustomMetric(name, value) // 如：近场同步耗时、重试次数等
}