ios - 从 ble swift 读取值的问题

Question

我正在做一个 ble 应用程序，当我尝试从 ble 设备读取值时，我需要从中获取一些值，它第一次返回 nil，当我返回并再次执行时，它返回值。在下面的代码中，我试图获取固件版本和电池的值。我第一次运行代码，它始终为固件版本和电池返回值返回 nil。请帮助弄清楚为什么我在第一次执行时没有收到固件版本的值。

这是我的代码

extension SearchDeviceViewController: CBCentralManagerDelegate, CBPeripheralDelegate {
    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        switch central.state {
        case .unknown:
            print("central.state is .unknown")
        case .resetting:
            print("central.state is .resetting")
        case .unsupported:
            print("central.state is .unsupported")
        case .unauthorized:
            print("central.state is .unauthorized")
        case .poweredOff:
            print("central.state is .poweredOff")
        case .poweredOn:
            print("central.state is .poweredOn")
            centralManager.scanForPeripherals(withServices: nil)
        @unknown default:
            print("\(central.state)")
        }
    }
    
    //establish a connection with detected BLE device
    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
        var dataFound = 0
        for peripheralsFound in peripherals {
            if peripheral.identifier == peripheralsFound.identifier {
                dataFound = 1
            }
        }
        if dataFound == 0 && peripheral.name != nil {
            if !deviceIds.contains(peripheral.identifier.uuidString) {
                peripherals.append(peripheral)
                tblViewDeviceList.reloadData()
            }
        }
    }
    
    //On successful connection, request for all the services available in the BLE device
    func centralManager(_ central: CBCentralManager, didConnect peripheral: CBPeripheral) {
        print("connected")
        selectedPeripheral.discoverServices(nil)
    }
    //Request all the characteristics available in each services
    func peripheral(_ peripheral: CBPeripheral, didDiscoverServices error: Error?) {
        print(4)
        var count = 1
        if let servicePeripheral = selectedPeripheral.services as [CBService]? { //get the services of the perifereal
            for service in servicePeripheral {
                //Then look for the characteristics of the services
                if service.uuid.uuidString == "6E400001-B5A3-F393-E0A9-E50E24DCCA9E" || service.uuid.uuidString == "180F" {
                    peripheral.discoverCharacteristics(nil, for: service)
                } else {
                    if count == 1 {
                        Alert.showAlertView(withTitle: "", withMessage: "Invalid device")
                        count = count + 1
                    }
                }
            }
        }
    }
    func peripheral(_ peripheral: CBPeripheral, didDiscoverCharacteristicsFor service: CBService, error: Error?) {
        print("5")
        
        if let characterArray = service.characteristics as [CBCharacteristic]? {
            for cc in characterArray {
                myCharacteristic = cc //saved it to send data in another function.
                if cc.uuid.uuidString == "6E400002-B5A3-F393-E0A9-E50E24DCCA9E" {
                    writeValue()
                } else {
                    peripheral.readValue(for: cc) //to read the value of the characteristic
                    peripheral.setNotifyValue(true, for: myCharacteristic)
                }
            }
        }
    }
    
    func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
            print("7")
            print(characteristic)
            if characteristic.uuid.uuidString == "6E400003-B5A3-F393-E0A9-E50E24DCCA9E" {
               
                if let readValue = characteristic.value {
                    if let datastring = NSString(data: readValue, encoding: String.Encoding.utf8.rawValue) {
                        self.firmware = datastring as String
                       
                    }
                }
            }
            
            if characteristic.uuid.uuidString == "2A19" {
               
                if let readValue = characteristic.value {
                    
                    let battery = readValue.compactMap({ String(format: "%02x", $0) }).joined()
                    if battery < "60" {
                        self.batteryStatus = "CHANGE"
                    } else if battery == "" {
                        self.batteryStatus = ""
                    } else {
                        self.batteryStatus = "OK"
                    }
                    if self.firmware != "" && battery != "" {
                        let storyboard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
                        let popupVC = storyboard.instantiateViewController(withIdentifier: "DeviceDetailsViewController") as! DeviceDetailsViewController
                        popupVC.deviceCount = defaults.integer(forKey: "devicesAdded")
                        popupVC.isNewDevice = true
                        popupVC.peripheralName = self.selectedPeripheral.name!
                        popupVC.deviceUUID = self.selectedPeripheral.identifier.uuidString
                        popupVC.fromSearch = true
                        popupVC.firmWare = self.firmware
                        popupVC.batteryStatus = self.batteryStatus
                        popupVC.modalPresentationStyle = .fullScreen
                        popupVC.modalTransitionStyle = .coverVertical
                        self.present(popupVC, animated: true, completion: nil)
                    }
                }
            }
        
    }
    
    func writeValue() {
        print("8")
        //Do something
        let setCmnd = "GET_FW_VERSION"
        let dataToSend: Data = setCmnd.data(using: String.Encoding.utf8)!
        selectedPeripheral.writeValue(dataToSend, for: myCharacteristic, type: CBCharacteristicWriteType.withResponse)
    }
    
    func centralManager(_ central: CBCentralManager, didFailToConnect peripheral: CBPeripheral, error: Error?) {
        
    }
}

标签： iosswiftxcodereturnbluetooth-lowenergy