Question

我是Swift和Mac / iO编程的新手。我在Macbook Pro上运行此示例，支持BLE并使用Xcode 7.3打开蓝牙。

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)
}

代码打印出来＆＃34;未知＆＃34;一遍又一遍，即使在很多分钟之后。我也尝试过设置委托，但是没有调用didUpdateState回调。我也尝试从命令行和Swift解释器运行它并得到相同的结果。

我必须遗漏一些非常基本的东西。如何报告CBCentralManager已启动？

Answer 1

我可以说，如果您不使用文档中列出的两个初始值设定项之一，那就是结果 - 您要使用其中一个：

init(delegate:queue:)

或：

init(delegate:queue:options:)

如果你打电话，Xcode不会抱怨：

CBCentralManager()

但如果你这样做，似乎你将无限期地留在CBCentralManagerState.Unknown。

如果您想进行实验，请在游乐场中粘贴此代码，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();

您将与代理人一起查看，它从Unknown开始，几乎立即调用委托，状态更改为PoweredOn，并且每个后续计时器显示{{1} }。

在没有委托的情况下执行相同的操作，使用空的初始化程序，并且永远不会调用委托方法（毫不奇怪）并且计时器触发将继续显示PoweredOn。

核心蓝牙CBCentralManager始终在Mac上将状态报告为“未知”

1 个答案: