无法发现任何服务，但可以连接到设备

Question

我能够连接到BLE设备，但是.discoverServices()不能工作。我的日志显示了一个无用的通用错误：[CoreBluetooth] XPC connection invalid

连接到它确实有效：

    func connectToPeripheral(id: Int) -> Bool {
        guard id >= 0 && id <= peripherals.count else {
            return false
        }
                
        let arrayItem = peripherals[id]
        connectedPeripheral = arrayItem.peripheral
        connectedPeripheral!.delegate = self

        myCentral.connect(connectedPeripheral!, options: nil)
        print("connected to \(arrayItem.name)")
        
        myCentral.stopScan()
        return true
    }
    
    func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
        print("Connected to \(String(describing: peripheral.name)) \(peripheral.description)!")
        print(peripheral.services as Any)
        peripheral.discoverServices(nil) 
    }

但是这个函数永远不会被调用。为什么？

    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        print("Services:")
        print(peripheral.services as Any)
    }

不知道我做错了什么，救命？

下面是完整的代码：

import Foundation
import CoreBluetooth

class BLEManager: NSObject, ObservableObject, CBCentralManagerDelegate, CBPeripheralDelegate {

    var myCentral: CBCentralManager!

    @Published var isSwitchedOn = false
    @Published var peripherals = [Peripheral]()
    @Published var connectedPeripheral: CBPeripheral?

    override init() {
        super.init()

        myCentral = CBCentralManager(delegate: self, queue: nil)
        myCentral.delegate = self
    }

    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
        var peripheralName: String!
       
        if let name = advertisementData[CBAdvertisementDataLocalNameKey] as? String {
            peripheralName = name
        } else {
            peripheralName = "Unknown"
        }
       
        if peripherals.contains(where: { p in p.name == peripheralName }) {
            return
        }
        
        let newPeripheral = Peripheral(id: peripherals.count, name: peripheralName, rssi: RSSI.intValue, peripheral: peripheral)
        peripherals.append(newPeripheral)
    }

    func startScanning() {
        print("startScanning")
        peripherals.removeAll()
        myCentral.scanForPeripherals(withServices: nil, options: nil)
    }

    func stopScanning() {
        print("stopScanning")
        myCentral.stopScan()
    }

    func connectToPeripheral(id: Int) -> Bool {
        guard id >= 0 && id <= peripherals.count else {
            return false
        }
                
        let arrayItem = peripherals[id]
        connectedPeripheral = arrayItem.peripheral
        connectedPeripheral!.delegate = self

        myCentral.connect(connectedPeripheral!, options: nil)
        print("connected to \(arrayItem.name)")
        
        myCentral.stopScan()
        return true
    }
    
    func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
        print("Connected to \(String(describing: peripheral.name)) \(peripheral.description)!")
        print(peripheral.services as Any)
        peripheral.discoverServices(nil)
    }

    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        print("Services:")
        print(peripheral.services as Any)
    }
    
    func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
        print("got Characteristics...")        
    }

    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        print("centralManagerDidUpdateState: poweredOn=\(central.state == .poweredOn)")
        
        if central.state == .poweredOn {
            //if it wasn't previously on, start scanning
            if !isSwitchedOn {
                isSwitchedOn = true
                startScanning()
            }
        } else {
            isSwitchedOn = false
        }
    }
}

struct Peripheral: Identifiable {
    let id: Int
    let name: String
    let rssi: Int
    let peripheral: CBPeripheral
}

Answer 1

我在代码中发现了两个bug。

1. I给startScanning()打电话时，centralManagerDidUpdateState()和central.state == .poweredOn一起被调用。这导致扫描在调用myCentral.connect(connectedPeripheral!, options: nil)
2. Calling myCentral.stopScan()之后再次启动，而myCentral.connect(connectedPeripheral!, options: nil)是导致myCentral.connect(connectedPeripheral!, options: nil)的原因之一。

我不明白为什么会发生这两种情况，但修复它们使我现在可以连接并获得服务和特性！