NWPathMonitor在监控互联网连接时出错

Question

我正在开发一个Swift应用程序，我需要知道设备何时连接到互联网，我实现了以下代码来实现这一点。

import Foundation
import Network
class NetworkMonitor: ObservableObject{

static let shared = NetworkMonitor()
private let queue = DispatchQueue.global()
private let monitor: NWPathMonitor
public private(set)var isConnected :Bool=false
public private(set)var connectionType :ConnectionType = .unknown

enum ConnectionType{
case wifi
case cellular
case unknown
}

init(){
monitor = NWPathMonitor()
}

public func startMonitoring(){

monitor.pathUpdateHandler={[weak self] path in
self?.isConnected=path.status == .satisfied
self?.getConnectionType(path)
}

monitor.start(queue: queue)
}

public func stopMonitoring(){
monitor.cancel()
}
public func getConnectionType(_ path: NWPath){
if(path.usesInterfaceType(.wifi)){
connectionType = .wifi
}else if(path.usesInterfaceType(.cellular)){
connectionType = .cellular
}else{
connectionType = .unknown
}
}
}

在调用函数startMonitoring()时出现问题。一切似乎工作正常，但我得到这个错误信息在控制台

2022-12-01 13:04:37.327650+0100 Luuk[11692:1287784] [] nw_path_evaluator_set_queue Client error: set queue after starting
2022-12-01 13:04:37.328799+0100 Luuk[11692:1287784] [] nw_path_evaluator_set_queue Client error: set queue after starting, dumping backtrace:
[arm64] libnetcore-2750.120.19.0.1
0   libnetwork.dylib                    0x0000000181950d4c __nw_create_backtrace_string + 192
1   libnetwork.dylib                    0x0000000181166f70 nw_path_evaluator_set_queue + 304
2   libnetwork.dylib                    0x00000001811841f8 nw_path_monitor_set_queue + 96
3   libswiftNetwork.dylib               0x00000001f0846ee4 $s7Network13NWPathMonitorC5start5queueySo012OS_dispatch_E0C_tF + 72
4   Luuk                                0x0000000104cfa418 $s4Luuk14NetworkMonitorC15startMonitoringyyF + 216
5   Luuk                                0x0000000104c7d010 $s4Luuk11SummaryViewV4bodyQrvgyycfU1_yyScMYccfU_ + 56
6   Luuk                                0x0000000104c137e0 $sIeg_IeyB_TR + 48
7   libdispatch.dylib                   0x0000000105640c70 _dispatch_call_block_and_release + 32
8   libdispatch.dylib                   0x00000001056427c0 _dispatch_client_callout + 20
9   libdispatch.dylib                   0x0000000105652c68 _dispatch_main_queue_drain + 1204
10  libdispatch.dylib                   0x00000001056527a4 _dispatch_main_queue_callback_4CF + 44
11  CoreFoundation                      0x00000001803fe800 5198FB57-5645-3B34-A49F-F32B52256CF3 + 333824
12  CoreFoundation                      0x00000001803b8704 5198FB57-5645-3B34-A49F-F32B52256CF3 + 46852
13  CoreFoundation                      0x00000001803cbbc8 CFRunLoopRunSpecific + 600
14  GraphicsServices                    0x000000019c4ff374 GSEventRunModal + 164
15  UIKitCore                           0x0000000182d3b648 3ED35565-456D-33CB-B554-6C567FA81585 + 5326408
16  UIKitCore                           0x0000000182abcd90 UIApplicationMain + 364
17  SwiftUI                             0x000000018821df24 5B6954AE-CE76-34AC-90F9-F7A8DEE0910F + 2359076
18  SwiftUI                             0x000000018814be08 5B6954AE-CE76-34AC-90F9-F7A8DEE0910F + 1498632
19  SwiftUI                             0x000000018812d0f4 $s7SwiftUI3AppPAAE4mainyyFZ + 128
20  Luuk                                0x0000000104ce5318 $s4Luuk0A3AppV5$mainyyFZ + 40
21  Luuk                                0x0000000104ce53c0 main + 12
22  dyld                                0x000000010540dce4 start + 520

我在网上搜索了，但是没有很多关于这种错误的信息。如有任何帮助，不胜感激。

当我注释掉

一行时

monitor.start(queue: queue)

错误消失

Answer 1

该错误可能是由于在取消NWPathMonitor后重复使用相同的实例而引起的-如下所述-

当NWPathMonitor实例被取消时，你不能再次使用start()。唯一的方法就是创建一个新的实例。

如果您试图取消->从同一个实例开始，您可以检查代码吗?

---

另外，我想说你应该改变你设置start()的队列，而不是全局的，你可以为此目的设置一个特定的

DispatchQueue(label: "NetworkMonitor")

，甚至使用主线程。