如何检测 iOS 14 中是否授予本地网络权限

iOS 14 如何检测用户是否在应用程序中授予了本地网络权限？如果用户拒绝权限并重定向到操作系统设置以授予权限，我必须显示错误屏幕。 苹果是否提供了类似位置许可之类的查找方式？

我编写了这个类，如果您不是使用 iOS 14.2，则可以使用该类。

• 此类将提示用户授予访问本地网络的权限（第一次）。
• 验证现有权限状态（如果已被拒绝/授予）。

请记住，该实例必须保持活动状态，因此如果您在另一个类的函数调用中使用它，则需要在调用函数的范围之外保持该实例活动状态。

import UIKit
import Network

class LocalNetworkPermissionChecker {
    private var host: String
    private var port: UInt16
    private var checkPermissionStatus: DispatchWorkItem?
    
    private lazy var detectDeclineTimer: Timer? = Timer.scheduledTimer(
        withTimeInterval: .zero,
        repeats: false,
        block: { [weak self] _ in
            guard let checkPermissionStatus = self?.checkPermissionStatus else { return }
            DispatchQueue.main.asyncAfter(deadline: .now(), execute: checkPermissionStatus)
        })
    
    init(host: String, port: UInt16, granted: @escaping () -> Void, failure: @escaping (Error?) -> Void) {
        self.host = host
        self.port = port
        
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationIsInBackground),
            name: UIApplication.willResignActiveNotification,
            object: nil)
        
        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationIsInForeground),
            name: UIApplication.didBecomeActiveNotification,
            object: nil)
        
        actionRequestNetworkPermissions(granted: granted, failure: failure)
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    /// Creating a network connection prompts the user for permission to access the local network. We do not have the need to actually send anything over the connection.
    /// - Note: The user will only be prompted once for permission to access the local network. The first time they do this the app will be placed in the background while
    /// the user is being prompted. We check for this to occur. If it does we invalidate our timer and allow the user to make a selection. When the app returns to the foreground
    /// verify what they selected. If this is not the first time they are on this screen, the timer will not be invalidated and we will check the dispatchWorkItem block to see what
    /// their selection was previously.
    /// - Parameters:
    ///   - granted: Informs application that user has provided us with local network permission.
    ///   - failure: Something went awry.
    private func actionRequestNetworkPermissions(granted: @escaping () -> Void, failure: @escaping (Error?) -> Void) {
        guard let port = NWEndpoint.Port(rawValue: port) else { return }
        
        let connection = NWConnection(host: NWEndpoint.Host(host), port: port, using: .udp)
        connection.start(queue: .main)
        
        checkPermissionStatus = DispatchWorkItem(block: { [weak self] in
            if connection.state == .ready {
                self?.detectDeclineTimer?.invalidate()
                granted()
            } else {
                failure(nil)
            }
        })
        
        detectDeclineTimer?.fireDate = Date() + 1
    }
    
    /// Permission prompt will throw the application in to the background and invalidate the timer.
    @objc private func applicationIsInBackground() {
        detectDeclineTimer?.invalidate()
    }
    
    /// - Important: DispatchWorkItem must be called after 1sec otherwise we are calling before the user state is updated.
    @objc private func applicationIsInForeground() {
        guard let checkPermissionStatus = checkPermissionStatus else { return }
        DispatchQueue.main.asyncAfter(deadline: .now() + 1, execute: checkPermissionStatus)
    }
}

//Can be used like this:
LocalNetworkPermissionChecker(host: "255.255.255.255", port: 4567, granted: {
    //Perform some action here...
},
failure: { error in
    if let error = error {
        print("Failed with error: \(error.localizedDescription)")
    }
})