Xamarin安卓应用启用WiFi连接代码后启动即崩溃无日志问题

问题说明 #

我写了一段Xamarin Android代码，用来获取WiFi网络信息并连接指定WiFi。代码里有两段被注释的逻辑，取消注释启用后，应用启动直接崩溃，连日志都打不出来，加了try/catch也抓不到异常。我知道把逻辑塞MainActivity里是不良实践，但这只是学习测试用，而且已经在应用信息页面手动给了所有需要的权限。

AndroidManifest.xml 关键配置 #

<!-- 声明的权限 -->
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />

<application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

MainActivity.cs 核心代码（含崩溃触发逻辑） #

using Android.App;
using Android.Content;
using Android.Net.Wifi;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace WifiTestApp
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : Activity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            SetContentView(Resource.Layout.activity_main);

            try
            {
                WifiManager wifiManager = (WifiManager)GetSystemService(WifiService);
                
                // 注释1：取消注释后触发崩溃的WiFi扫描逻辑
                //List<ScanResult> scanResults = wifiManager.ScanResults.ToList();
                //foreach (var result in scanResults)
                //{
                //    Console.WriteLine($"SSID: {result.Ssid}, RSSI: {result.Level}");
                //}

                // 注释2：取消注释后触发崩溃的WiFi连接逻辑
                //WifiConfiguration config = new WifiConfiguration();
                //config.Ssid = "\"TestWiFi\"";
                //config.PreSharedKey = "\"TestPassword123\"";
                //int networkId = wifiManager.AddNetwork(config);
                //wifiManager.Disconnect();
                //wifiManager.EnableNetwork(networkId, true);
                //wifiManager.Reconnect();
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Exception: {ex.Message}");
                Toast.MakeText(this, ex.Message, ToastLength.Long).Show();
            }
        }

        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }
}

设备日志关键报错信息 #

从设备崩溃日志中提取到核心原因：

AndroidRuntime: FATAL EXCEPTION: main
Process: WifiTestApp.WifiTestApp, PID: 18765
java.lang.SecurityException: WifiService: Neither user 10156 nor current process has android.permission.ACCESS_FINE_LOCATION.

解决办法 #

1. 补全动态权限请求逻辑
   Android 6.0（API 23）及以上，危险权限（如ACCESS_FINE_LOCATION）仅在Manifest声明+手动授予还不够，必须在代码中触发运行时权限检查。手动授予后系统可能未更新进程的权限状态，导致权限异常。修改MainActivity代码添加权限检查：

const int RequestLocationPermission = 0;
string[] requiredPermissions = { Android.Manifest.Permission.AccessFineLocation };

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    Xamarin.Essentials.Platform.Init(this, savedInstanceState);
    SetContentView(Resource.Layout.activity_main);

    // 先检查位置权限
    if (CheckSelfPermission(Android.Manifest.Permission.AccessFineLocation) != Android.Content.PM.Permission.Granted)
    {
        RequestPermissions(requiredPermissions, RequestLocationPermission);
        return;
    }

    // 权限通过后执行WiFi逻辑
    ExecuteWifiOperations();
}

private void ExecuteWifiOperations()
{
    try
    {
        WifiManager wifiManager = (WifiManager)GetSystemService(WifiService);
        
        // 启用WiFi扫描逻辑
        List<ScanResult> scanResults = wifiManager.ScanResults.ToList();
        foreach (var result in scanResults)
        {
            Console.WriteLine($"SSID: {result.Ssid}, RSSI: {result.Level}");
        }

        // 启用WiFi连接逻辑
        WifiConfiguration config = new WifiConfiguration();
        config.Ssid = "\"TestWiFi\"";
        config.PreSharedKey = "\"TestPassword123\"";
        int networkId = wifiManager.AddNetwork(config);
        wifiManager.Disconnect();
        wifiManager.EnableNetwork(networkId, true);
        wifiManager.Reconnect();
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Exception: {ex.Message}");
        Toast.MakeText(this, ex.Message, ToastLength.Long).Show();
    }
}

public override void OnRequestPermissionsResult(int requestCode, string[] permissions, Android.Content.PM.Permission[] grantResults)
{
    base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
    if (requestCode == RequestLocationPermission)
    {
        if (grantResults.Length > 0 && grantResults[0] == Android.Content.PM.Permission.Granted)
        {
            // 权限授予后执行WiFi操作
            ExecuteWifiOperations();
        }
        else
        {
            Toast.MakeText(this, "必须授予位置权限才能获取WiFi信息", ToastLength.Long).Show();
        }
    }
}

2. 检查设备位置服务状态
   Android 8.0及以上版本，获取WiFi扫描结果不仅需要位置权限，还要求设备的位置服务处于开启状态。可以添加检查逻辑引导用户开启：

// 在ExecuteWifiOperations方法开头添加
LocationManager locationManager = (LocationManager)GetSystemService(LocationService);
if (!locationManager.IsProviderEnabled(LocationManager.GpsProvider) && !locationManager.IsProviderEnabled(LocationManager.NetworkProvider))
{
    Intent openLocationSettings = new Intent(Android.Provider.Settings.ActionLocationSourceSettings);
    StartActivity(openLocationSettings);
    Toast.MakeText(this, "请开启位置服务以获取WiFi信息", ToastLength.Long).Show();
    return;
}

3. 避免在OnCreate中直接执行敏感操作
   即使是测试，也建议将WiFi扫描、连接逻辑放到异步线程或OnResume生命周期中执行，避免阻塞UI线程导致崩溃或ANR。

内容的提问来源于stack exchange，提问作者Éder Rocha