在 iOS 上检测 WiFi 启用/禁用的更好方法？

Question

经过难以置信的咬牙切齿后，我终于有了一种方法，可以成功检测 iOS 上是否启用了 WiFi，而不管它是否连接。这样的东西至少有几个用途，我不认为这违反了 Apple Law(tm) 的精神或文字。

但是，它很丑陋，可能不会永远有效。截至 2017 年 1 月 31 日，它目前适用于 iOS 10.2.1。我将把我的答案放在下面，希望有人可以改进它。我对可达性（不满足要求）、CaptiveNetwork、HotspotHelper、SCNetworkConfiguration、Xamarin 的 System.Net.NetworkInterface 等进行了大量研究。据我所知，这就是它真正有效的方法。

Answer 1

解决方案的要点是，当 getifaddrs() 报告了两个名称为“awdl0”的接口时，WiFi 就会启用。只有一个，它已被禁用。

我感谢 pebble8888 将我指向 https://github.com/alirp88/SMTWiFiStatus，它是 Objective-C，由于缺少 cmets，因此很难理解正在发生的事情或作者的意图。

这是我完整且完整的 Xamarin/C# 解决方案，对于任何其他主要语言用户来说应该都非常易读：

using System;
using System.Runtime.InteropServices;

namespace Beacon.iOS
{
/// <summary>
/// code stolen from the Xamarin source code to work around goofy interactions between
/// the good-god-why-would-it-work-that-way iOS and the entirely reasonable Xamarin
/// (it doesn't report interfaces that are reported multiple times)
/// </summary>
class XamHack
{
    //
    // Types
    //
    internal struct ifaddrs
    {
#pragma warning disable 0649
        public IntPtr ifa_next;
        public string ifa_name;
        public uint ifa_flags;
        public IntPtr ifa_addr;
        public IntPtr ifa_netmask;
        public IntPtr ifa_dstaddr;
        public IntPtr ifa_data;
#pragma warning restore
    }

    //
    // OS methods
    //
    [DllImport("libc")]
    protected static extern int getifaddrs(out IntPtr ifap);

    [DllImport("libc")]
    protected static extern void freeifaddrs(IntPtr ifap);


    //
    // Methods
    //

    /// <summary>
    /// Our glorious hack.  I apologize to the programming gods for my sins
    /// but this works (for now) and functionality trumps elegance.  Even this.
    /// Reverse engineered from: https://github.com/alirp88/SMTWiFiStatus
    /// </summary>
    public static bool IsWifiEnabled()
    {
        int count = 0;
        IntPtr ifap;

        // get the OS to put info about all the NICs into a linked list of buffers
        if (getifaddrs(out ifap) != 0)
            throw new SystemException("getifaddrs() failed");

        try
        {
            // iterate throug those buffers
            IntPtr next = ifap;
            while (next != IntPtr.Zero)
            {
                // marshall the data into our struct
                ifaddrs addr = (ifaddrs)Marshal.PtrToStructure(next, typeof(ifaddrs));

                // count the instances of the sacred interface name
                if ("awdl0" == addr.ifa_name)
                    count++;

                // move on to the next interface
                next = addr.ifa_next;
            }
        }
        finally
        {
            // leaking memory is for jerks
            freeifaddrs(ifap);
        }

        // if there's two of the sacred interface, that means WiFi is enabled.  Seriously.
        return (2 == count);
    }

} // class
} // namespace