ios - 核心蓝牙 CBCentralManager 在 Mac 上始终将状态报告为未知

Question

总体而言，我是 Swift 和 Mac/iOs 编程的新手。我正在使用 Xcode 7.3 在支持 BLE 并打开蓝牙的 Macbook Pro 上运行此示例。

import Foundation
import CoreBluetooth

func printState(state: CBCentralManagerState) {
    switch state {
    case CBCentralManagerState.PoweredOn:
        print("Powered on")
    case CBCentralManagerState.PoweredOff:
        print("Powered off")
    case CBCentralManagerState.Resetting:
        print("Resetting")
    case CBCentralManagerState.Unauthorized:
        print("Unauthorized")
    case CBCentralManagerState.Unknown:
        print("Unknown")
    default:
        print ("Unsupported")
    }

}

var myCentralManager = CBCentralManager(delegate:nil, queue:nil)
while true {
    printState(myCentralManager.state)
    sleep(1)
}

代码一遍又一遍地打印出“Unknown”，甚至在几分钟后也是如此。我也试过设置一个委托(delegate)，但没有调用 didUpdateState 回调。我还尝试从命令行和 Swift 解释器运行它并获得相同的结果。

我一定是遗漏了一些非常基本的东西。我怎样才能让它报告 CBCentralManager 已开机？

Answer 1

据我所知，如果您不使用文档中列出的两个初始化器之一，这就是结果——您想使用其中一个:

init(delegate:queue:)

或:

init(delegate:queue:options:)

如果您只是调用，Xcode 不会提示:

CBCentralManager()

但如果你这样做，你似乎会无限期地留在 CBCentralManagerState.Unknown 中。

如果您想进行试验，请制作一个 Playground 并粘贴此代码，然后使用我列出的两个初始化程序变体进行尝试:

import Cocoa
import CoreBluetooth
import XCPlayground

@objc
public class BluetoothWatcher: NSObject, CBCentralManagerDelegate {
    var cbcm: CBCentralManager!;
    var timer: NSTimer!;

    override init() {
        super.init();

        /*:
            When you initialize a central manager, the delegate seems important. If you comment out the initializer with the delegate and uncomment the other one, it'll stay in state unknown indefinitely.
        */
        //cbcm = CBCentralManager(delegate: self, queue:nil);
        cbcm = CBCentralManager();

        checkStateInOneSecond();
    }

    public func centralManagerDidUpdateState(central: CBCentralManager) {
        print( "State updated: \(stateString())" );
    }

    func checkStateInOneSecond() {
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (Int64)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), {
            self.checkState();
        });
    }

    public func checkState() {
        print( "Timer fired, state: \(stateString())" );
        checkStateInOneSecond();
    }

    func stateString() -> String {
        switch(cbcm.state) {
        case .Resetting:
            return "resetting"
        case .PoweredOn:
            return "powered on";
        case .PoweredOff:
            return "powered off";
        case .Unknown:
            return "unknown";
        case .Unsupported:
            return "unsupported";
        case .Unauthorized:
            return "unauthorized";
        }
    }
}


XCPlaygroundPage.currentPage.needsIndefiniteExecution = true;
var watcher = BluetoothWatcher();

您会看到委托(delegate)，它从 Unknown 开始，几乎立即调用委托(delegate)并将状态更改为 PoweredOn，并且每个后续计时器触发都显示开机。

在没有委托(delegate)的情况下做同样的事情，使用空的初始值设定项，委托(delegate)方法将永远不会被调用(毫不奇怪)并且计时器触发将继续显示 Unknown。