iOS CenteralManager没有回调状态变化

Question

我正在Swift中编写我的第一个BLE应用程序并遇到了障碍。我的中央管理器状态更改事件处理程序仅在应用程序启动时调用，并且在viewDidLoad（）中初始化了管理器。我可以在没有回电的情况下关闭和打开BLE。以下代码段;任何帮助都会受到欢迎。

class ViewController: UIViewController, CBCentralManagerDelegate, UITextFieldDelegate, UITableViewDataSource, UITableViewDelegate, CBPeripheralDelegate
{
    //MARK: Properties

    var btManager: CBCentralManager!


    override func viewDidLoad()
    {
        super.viewDidLoad()

        // Initialize CoreBluetooth Central Manager
        btManager = CBCentralManager(delegate: self, queue: nil)
    }


    // Called when BLE changes state
    func centralManagerDidUpdateState(_ central: CBCentralManager)
    {
        switch central.state
        {
            case .poweredOn:
                NSLog("BLE powered on")

            case .poweredOff:
                NSLog("BLE powered off")

            case .unsupported:
                NSLog("BLE unsupported")

            case .unauthorized:
                NSLog("BLE unauthorized")

            case .resetting:
                NSLog("BLE reseting")

            case .unknown:
                NSLog("BLE unknown")
        }
    }
}