Question

我正在尝试获取可用wifi网络的列表并将其显示在列表视图中。在PCL项目中，我创建了一个接口“ IWifiService”。

 public interface IWifiService
{
    void GetWifiList();
}

在android项目中，使用WifiService类来获取所有网络列表。

[assembly:Dependency(typeof(WifiService))]
namespace WifiConnectivity.Droid.WifiService
{
public class WifiService : IWifiService
{
    private static WifiManager wifi;
    private WifiReceiver wifiReceiver;
    public static List<string> WiFiNetworks;

    public void GetWifiList()
    {
        WiFiNetworks = new List<string>();
        var context = Android.App.Application.Context;
        wifi = (WifiManager)context.GetSystemService(Context.WifiService);
        wifiReceiver = new WifiReceiver();
        context.RegisterReceiver(wifiReceiver, new IntentFilter(WifiManager.ScanResultsAvailableAction));
        wifi.StartScan();

    }

    public class WifiReceiver : BroadcastReceiver
    {
        public override void OnReceive(Context context, Intent intent)
        {
            IList<ScanResult> scanWifiNetworks = wifi.ScanResults;
            foreach(ScanResult wifinetwork in scanWifiNetworks)
            {
                WiFiNetworks.Add(wifinetwork.Ssid);
            }
        }
    }
}

}

然后从ViewModel中，我像这样调用依赖服务：

 var service = DependencyService.Get<IWifiService>();
        service.GetWifiList();

现在，类WifiReceiver无法返回任何内容，因此我无法在ViewModel中获取那些网络列表。如何将这个列表放入ViewModel中？

Answer 1

我建议您在GetWifiList方法中返回一个列表，以便界面看起来像这样：

 public interface IWifiService
 {
    void GetWifiList(Action<List<string>> action);
 }

然后您的GetWifiList方法将如下所示：

public static Action<List<string>> CallBackAction;

public void GetWifiList(Action<List<string>> callBackMethod)
{
    WiFiNetworks = new List<string>();
    var context = Android.App.Application.Context;
    wifi = (WifiManager)context.GetSystemService(Context.WifiService);
    wifiReceiver = new WifiReceiver();
    context.RegisterReceiver(wifiReceiver, new IntentFilter(WifiManager.ScanResultsAvailableAction));
    wifi.StartScan();
    CallBackAction= callBackMethod;
}

然后在OnRecieve方法中执行回调方法：

public override void OnReceive(Context context, Intent intent)
    {
        IList<ScanResult> scanWifiNetworks = wifi.ScanResults;
        foreach(ScanResult wifinetwork in scanWifiNetworks)
        {
            WiFiNetworks.Add(wifinetwork.Ssid);
        }
        CallBackAction(WiFiNetworks);
    }

现在，回调方法中最重要的部分以及作为参数传递的内容：

System.Action基本上是一个方法引用，您可以在其中传递回调方法的名称，如下所示：

    var service = DependencyService.Get<IWifiService>();
    service.GetWifiList(MyCallBackAction);

MyCallBackAction如下：

   public void MyCallBackAction(List<string> wifiNetworks)
   {
    // this method will be called every time you get a callback at OnRecieve
   }

从Android项目到ViewModel的数据绑定

1 个答案: