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01 - iOS 蓝牙与云服务全栈
目录
1. Core Bluetooth 架构
1.1 CBPeripheralManager 和 CBCentralManager
Core Bluetooth 角色：
┌──────────────┐ ←─ 中央设备 (Central) ──→ 外设
│ CBCentral │ (扫描、连接、请求服务)
│ Manager │
└──────────────┘
⇅ BLE 通信 (GATT 协议)
┌──────────────┐ ←─ 外设设备 (Peripheral) ──→ 中央
│ CBPeripheral │ (广播、接收连接)
│ Manager │
└──────────────┘
GATT 层级结构：
┌─────────────────────────┐
│ Service (服务) │ ← 功能组
│ ┌───────────────┐ │
│ │ Characteristic │ │ ← 数据单元
│ │ (UUID + 值) │ │
│ │ Properties: │ │
│ │ - Read │ │
│ │ - Write │ │
│ │ - Notify │ │
│ └───────────────┘ │
│ ┌───────────────┐ │
│ │ Characteristic │ │
│ └───────────────┘ │
└──────────────────────────┘1.2 Central 设备（扫描连接）
swift
class BluetoothManager: NSObject, CBCentralManagerDelegate, CBPeripheralDelegate {
private var centralManager: CBCentralManager!
private var connectedPeripheral: CBPeripheral?
override init() {
super.init()
centralManager = CBCentralManager(delegate: self, queue: .main)
}
// MARK: - CBCentralManagerDelegate
func centralManagerDidUpdateState(_ central: CBCentralManager) {
switch central.state {
case .poweredOn:
centralManager.scanForPeripherals(
withServices: [UUID(uuidString: "your-service-uuid")!],
options: [CBCentralManagerScanOptionAllowDuplicatesKey: false]
)
case .poweredOff, .unsupported, .unauthorized:
print("蓝牙不可用")
default:
break
}
}
func centralManager(_ central: CBCentralManager,
didDiscover peripheral: CBPeripheral,
advertisementData: [String: Any],
rssi RSSI: NSNumber) {
// 发现外设，可连接
connectedPeripheral = peripheral
peripheral.delegate = self
central.connect(peripheral, options: nil)
}
func centralManager(_ central: CBCentralManager,
didConnect peripheral: CBPeripheral) {
// 发现服务
peripheral.discoverServices([UUID(uuidString: "your-service-uuid")!])
}
// MARK: - CBPeripheralDelegate
func peripheral(_ peripheral: CBPeripheral,
didDiscoverServices error: Error?) {
guard let services = peripheral.services else { return }
for service in services {
peripheral.discoverCharacteristics(nil, for: service)
}
}
func peripheral(_ peripheral: CBPeripheral,
didDiscoverCharacteristicsFor service: CBService,
error: Error?) {
guard let characteristics = service.characteristics else { return }
for char in characteristics {
if char.properties.contains(.notify) {
peripheral.setNotifyValue(true, for: char)
}
}
}
func peripheral(_ peripheral: CBPeripheral,
didUpdateValueFor characteristic: CBCharacteristic,
error: Error?) {
guard let data = characteristic.value else { return }
// 处理接收到的数据
print("收到数据: \(data)")
}
// 发送数据
func sendData(_ data: Data) {
guard let peripheral = connectedPeripheral else { return }
// 找到可写的 characteristic
peripheral.writeValue(data, for: characteristic, type: .withResponse)
}
}1.3 Peripheral 设备（广播数据）
swift
class PeripheralManager: NSObject, CBPeripheralManagerDelegate {
private var peripheralManager: CBPeripheralManager!
override init() {
super.init()
peripheralManager = CBPeripheralManager(delegate: self, queue: .main)
}
// MARK: - 广播服务
func advertise() {
let serviceUUIDs = [CBUUID(string: "your-service-uuid")]
let advertisement: [String: Any] = [
CBAdvertisementDataServiceUUIDsKey: serviceUUIDs,
CBAdvertisementDataLocalNameKey: "MyDevice"
]
peripheralManager.startAdvertising(advertisement)
}
// MARK: - CBPeripheralManagerDelegate
func peripheralDidUpdateState(_ peripheral: CBPeripheralManager) {
if peripheral.state == .poweredOn {
// 添加服务
let characteristic = CBMutableCharacteristic(
type: CBUUID(string: "your-char-uuid"),
properties: .read | .write | .notify,
value: nil,
permissions: .readable | .writeable
)
let service = CBMutableService(type: CBUUID(string: "your-service-uuid"), primary: true)
service?.characteristics = [characteristic]
peripheralManager.add(service!)
peripheralManager.startAdvertising([
CBAdvertisementDataLocalNameKey: "MyDevice"
])
}
}
func peripheral(_ peripheral: CBPeripheralManager,
didReceiveWriteRequests request: [CBATTRequest]) {
for req in request {
// 处理写入请求
req.value = req.value
peripheral.respond(to: req, with: .success)
}
}
}2. BLE 通信流程
BLE 通信流程：
Central 设备: Peripheral 设备:
┌──────────┐ ┌──────────┐
│ 扫描外设 │───→ CBAdvertisementData ───→│ 广播数据 │
│ │ │ │
│ 连接外设 │───→ L2CAP 连接 ────────────→│ 接收连接 │
│ │ │ │
│ 发现服务 │───→ GATT Discover ────────→│ 注册服务 │
│ │ │ │
│ 读写特征 │───→ GATT Read/Write ─────→│ 读写特征 │
│ │ │ │
│ 订阅通知 │───→ GATT Notify ──────────→│ 推送通知 │
└──────────┘ └──────────┘
GATT 协议栈：
┌─────────────┐
│ Application │ BLE 应用层
│ Profile │ (GATT Profile)
├─────────────┤
│ GATT │ 通用属性配置文件
├─────────────┤
│ ATT │ 属性传输协议
├─────────────┤
│ L2CAP │ 逻辑链路控制
├─────────────┤
│ HCI │ 主机控制接口
├─────────────┤
│ BLE Radio │ 蓝牙无线电
└─────────────┘3. 蓝牙权限与适配
3.1 Info.plist 配置
xml
<!-- iOS 13+ -->
<key>NSBluetoothAlwaysUsageDescription</key>
<string>需要使用蓝牙连接设备</string>
<!-- iOS 12 及以下 -->
<key>NSBluetoothPeripheralUsageDescription</key>
<string>需要使用蓝牙连接设备</string>
<!-- Core Bluetooth 无需额外权限声明 -->3.2 蓝牙权限状态
| 状态 | 说明 |
|---|---|
| .poweredOn | 可用 |
| .poweredOff | 用户关闭 |
| .resetting | 蓝牙重置中 |
| .unauthorized | 应用无权限 |
| .unsupported | 设备不支持 |
| .restricted | 系统限制（家长控制） |
3.3 最大传输单元
BLE MTU（最大传输单元）：
• 默认 MTU: 23 bytes (20 bytes payload + 3 bytes header)
• 协商 MTU: 通过 exchangeMTU 请求增大
• 典型协商结果: 150-512 bytes（取决于硬件）
// 请求增大 MTU
peripheral.maximumWriteValueLength(for: .withResponse)
// 有响应写入的最大长度
peripheral.maximumWriteValueLength(for: .withoutResponse)
// 无响应写入的最大长度4. Background Modes
4.1 后台蓝牙模式
Core Bluetooth 后台模式：
┌───────────────────────────────────────────┐
│ Info.plist → Background Modes → Bluetooth │
│ LE accessories │
├─────────────────────────────────────────────┤
│ • App 在后台时仍可扫描/连接外设 │
│ • 系统会重启你的 app 处理事件 │
│ • 需实现 CBCentralManagerDelegate 的 │
│ centralManager:restorePeripherals │
│ 恢复外设列表 │
└─────────────────────────────────────────────┘
恢复外设：
func centralManager(_ central: CBCentralManager,
restoreConnectedPeripherals profiles: [CBPeripheral]) {
for peripheral in profiles {
// 恢复连接状态
}
}5. CloudKit 核心
5.1 CloudKit 架构
CloudKit 架构：
┌───────────────────────────────────────────┐
│ CloudKit │
├────────────────────────────────────────┬──┤
│ Public Database │ Private DB │ │
│ (共享数据) │ (用户私有) │ │
├───────────────────┼────────────────┬──┤
│ CKRecord │ CKRecord │ │
│ CKQuery │ CKQuery │ │
│ CKSubscription │ CKSubscription │ │
├───────────────────┼────────────────┬──┤
│ CKContainer │ CKDatabase │ │
│ (容器) │ (数据库) │ │
├───────────────────┼────────────────┬──┤
│ CKRecordZone │ CKRecordZone │ │
│ (记录区) │ │ │
└───────────────────┴────────────────┴──┘5.2 CloudKit 基本操作
swift
import CloudKit
let container = CKContainer(identifier: "iCloud.com.your.app")
let publicDB = container.publicCloudDatabase
let privateDB = container.privateCloudDatabase
// 保存记录
let record = CKRecord(recordType: "User", recordID: CKRecord.ID())
record["name"] = "John"
record["age"] = 25
publicDB.save(record) { record, error in
if let error = error {
print("保存失败: \(error)")
} else {
print("保存成功")
}
}
// 查询记录
let predicate = NSPredicate(format: "name == %@", "John")
let query = CKQuery(recordType: "User", predicate: predicate)
publicDB.perform(query, inZoneWith: nil) { results, error in
for record in results ?? [] {
if let name = record["name"] as? String {
print("用户名: \(name)")
}
}
}
// 订阅记录
let subscription = CKRecordSubscription(recordType: "User")
subscription.events = .recordCreated
publicDB.save(subscription) { _, _ in }6. 后台任务
6.1 BGTaskScheduler
swift
import BackgroundTasks
// 注册后台任务
BGTaskScheduler.shared.register(forTaskWithIdentifier: "com.app.backgroundSync",
using: .main) { task in
handleBackgroundSync(task: task as! BGAppRefreshTask)
}
func handleBackgroundSync(task: BGAppRefreshTask) {
task.expirationHandler = {
task.setTaskCompleted(success: false)
}
// 执行后台任务（最多 30 秒）
performNetworkRequest { success in
task.setTaskCompleted(success: success)
}
}
// 调度任务
let request = BGAppRefreshTaskRequest(identifier: "com.app.backgroundSync")
request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60) // 15 分钟后
BGTaskScheduler.shared.submit(request)6.2 后台任务类型
| 类型 | 用途 | 最大时长 |
|---|---|---|
| BGAppRefreshTask | App 刷新 | 30s |
| BGMaintenanceTask | 系统维护 | 10s |
| BGProcessingTask | 长时间任务 | 10min |
| UIBackgroundTask | 前台延迟 | 3min |
7. 蓝牙与云服务 Android 对比
| 概念 | iOS | Android/Kotlin |
|---|---|---|
| 蓝牙 | Core Bluetooth (BLE) | BLE API (BluetoothGatt) |
| 角色 | Central/Peripheral | Device/Server/Client |
| GATT | CBService/CBCharacteristic | BluetoothGattService/Characteristic |
| 云服务 | CloudKit | Firebase / 自建后端 |
| 后台通信 | Background Modes + BLE | Foreground Service + BLE |
| 数据同步 | CKSubscription + CloudKit | Firebase Realtime DB |
8. 面试考点汇总
高频面试题
BLE 通信的核心概念？
- Central/Peripheral 角色
- Service → Characteristic 层级
- Read/Write/Notify 三种操作
iOS 蓝牙后台支持？
- 需要配置 Background Modes
- 系统自动恢复连接
- CBCentralManagerDelegate 的 restorePeripherals 回调
CloudKit 的数据库类型？
- Public Database：所有用户共享
- Private Database：用户私有
- 记录通过 CKRecord 管理
Background Tasks 有哪些类型？
- BGAppRefreshTask：App 刷新（30s）
- BGProcessingTask：长时间任务（10min）
- BGMaintenanceTask：系统维护（10s）
面试回答模板
"iOS 蓝牙用 Core Bluetooth 框架，Central 扫描连接 Peripheral，通过 Service/Characteristic 读写数据。支持后台模式，系统自动恢复连接。云服务用 CloudKit，分 Public 和 Private Database。后台任务用 BGTaskScheduler 调度。"
本文档对标 Android 30_Bluetooth + 31_Cloud_Background 的深度