WiFiP2PManager、OnPeersAvailable、DeviceList.Count 为零 - 始终

Posted 2023-02-23

【中文标题】WiFiP2PManager、OnPeersAvailable、DeviceList.Count 为零 - 始终

【英文标题】：WiFiP2PManager, OnPeersAvailable, DeviceList.Count zero - always

【发布时间】：2020-06-05 02:17:27

【问题描述】：

我已经在 2 部运行 Xamarin 测试应用程序的三星 S8 手机上苦苦挣扎了好几天，使用最少的 WiFiP2PManager 代码来发现同行。我已经翻遍了社区论坛和文档——不可能这么难，一定有我遗漏的东西。

我检查了常见的错误：

应用权限集 (ACCESS_FINE_LOCATION, ACCESS_COARSE_LOCATION, ACCESS_WIFI_STATE, CHANGE_WIFI_STATE, CHANGE_NETWORK_STATE, INTERNET) WiFi 直接打开了吗 两部手机是否都处于发现模式（或不同，结果相同）

尽管如此，OnPeersAvailable 还是使用 DeviceList 的空集合调用。

调试窗口中的调用顺序是：

WifiP2pManager.Initialize MainActivity.RegisterReceiver WifiP2pManager.DiscoverPeers WifiP2pManager.RequestPeers OnPeersAvailable (DeviceList.Count == 0)

这是我的代码，也许你能看到什么？

using System;

using android.App;
using Android.OS;
using Android.Support.V7.App;
using Android.Runtime;
using Android.Net.Wifi.P2p;
using Android.Content;
using static Android.Net.Wifi.P2p.WifiP2pManager;

namespace WiFiDirectTest

    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity, IChannelListener, IPeerListListener
    
        private WifiP2pManager manager;
        Channel channel;
        MyBroadcastReceiver receiver;

        protected override void OnCreate(Bundle savedInstanceState)
        
            base.OnCreate(savedInstanceState);

            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            SetContentView(Resource.Layout.activity_main);

            System.Diagnostics.Debug.WriteLine($"Wifi - initialize");
            manager = (WifiP2pManager)GetSystemService(WifiP2pService);
            channel = manager.Initialize(this, MainLooper, null);
        


        protected override void OnResume()
        
            base.OnResume();

            System.Diagnostics.Debug.WriteLine($"Wifi - register receiver");
            receiver = new MyBroadcastReceiver(manager, channel, this);
            receiver.Register(this);

            System.Diagnostics.Debug.WriteLine($"Wifi - discover peers");
            manager.DiscoverPeers(channel, new MyActionListner());
        


        protected override void OnPause()
        
            base.OnPause();

            System.Diagnostics.Debug.WriteLine($"Wifi - unregister receiver");
            receiver.Unregister(this);
            receiver = null;
        

        public void OnPeersAvailable(WifiP2pDeviceList peers)
        
            var count = peers.DeviceList.Count;
            System.Diagnostics.Debug.WriteLine($"Wifi - peers available: count");
        

        public void OnChannelDisconnected()
        
            System.Diagnostics.Debug.WriteLine("OnChannelDisconnected");
        

        private class MyActionListner : Java.Lang.Object, WifiP2pManager.IActionListener
        
            public MyActionListner()
            
            

            public void OnFailure(WifiP2pFailureReason reason)
            
                // breakpoint placed here, never reached.
            

            public void OnSuccess()
            
            
        
    


    public class MyBroadcastReceiver : BroadcastReceiver
    
        WifiP2pManager manager;
        WifiP2pManager.Channel channel;
        MainActivity activity;

        public MyBroadcastReceiver(WifiP2pManager manager, Channel channel, MainActivity activity)
        
            this.manager = manager;
            this.channel = channel;
            this.activity = activity;
        

        public void Register(MainActivity context)
        
            var intentFilter = new IntentFilter();

            intentFilter.AddAction(WifiP2pManager.WifiP2pStateChangedAction);
            intentFilter.AddAction(WifiP2pManager.WifiP2pPeersChangedAction);
            intentFilter.AddAction(WifiP2pManager.WifiP2pConnectionChangedAction);
            intentFilter.AddAction(WifiP2pManager.WifiP2pThisDeviceChangedAction);

            context.RegisterReceiver(this, intentFilter);
        

        public void Unregister(MainActivity context)
        
            context.UnregisterReceiver(this);
        

        public override void OnReceive(Context context, Intent intent)
        
            var action = intent.Action;

            if (WifiP2pManager.WifiP2pStateChangedAction.Equals(action))
            
                 System.Diagnostics.Debug.WriteLine("WifiP2pStateChangedAction");
            
            else if (WifiP2pManager.WifiP2pPeersChangedAction.Equals(action))
            
                System.Diagnostics.Debug.WriteLine($"Wifi - request peers");
                manager.RequestPeers(channel, activity);
            
            else if (WifiP2pManager.WifiP2pConnectionChangedAction.Equals(action))
            
                System.Diagnostics.Debug.WriteLine("WifiP2pConnectionChangedAction");
            
            else if (WifiP2pManager.WifiP2pThisDeviceChangedAction.Equals(action))
            
                System.Diagnostics.Debug.WriteLine("WifiP2pThisDeviceChangedAction");
            
        
    

有什么想法吗？

-约翰

【参考方案1】：

解决了！

原来我使用的WiFiDirectSample 是在 v6.0 (API 23) 中的新运行时权限功能之前使用旧 API 构建的。当我在我的新应用程序中模仿 WiFiP2PManager 编排时，我正在为 v9（API 28）构建。

因此，我需要在运行时明确请求权限，尽管它们已在 Android 清单中列出。我（一遍又一遍地）阅读的文档都没有提到请求权限。

        string[] permissions = 
            Manifest.Permission.AccessFineLocation,
            Manifest.Permission.AccessCoarseLocation,
            Manifest.Permission.AccessWifiState,
            Manifest.Permission.ChangeWifiState,
            Manifest.Permission.Internet
        ;
        RequestPermissions(permissions, 0);

所以我刚刚将此代码添加到我的OnCreate()，现在我在我的 OnPeersAvailable 回调中获得了同行！