C#自动重置事件未释放

使用Xamarin.Forms（用于iOS）我尝试实现功能，以等待用户确认已设置地理位置权限，然后再继续

我试图实现这一点的方法是让线程等待，直到使用

AutoResetEvent

触发事件

主要问题（我相信）在于以下代码：

manager.AuthorizationChanged += (object sender, CLAuthorizationChangedEventArgs args) => {

    Console.WriteLine ("Authorization changed to: {0}", args.Status);

    if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
        tcs.SetResult (args.Status == CLAuthorizationStatus.AuthorizedAlways || args.Status == CLAuthorizationStatus.AuthorizedWhenInUse);
    } else {
        tcs.SetResult (args.Status == CLAuthorizationStatus.Authorized);
    }

    _waitHandle.Set ();
};

manager.Failed += (object sender, Foundation.NSErrorEventArgs e) => {

    Console.WriteLine ("Authorization failed");

    tcs.SetResult (false);

    _waitHandle.Set ();
};

if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
    manager.RequestWhenInUseAuthorization ();
}

_waitHandle.WaitOne ();

您可以在下面找到完整的类：

public class LocationManager : ILocationManager
{
    static EventWaitHandle _waitHandle = new AutoResetEvent (false);

    private TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();

    public LocationManager ()
    {
    }

    public Task<bool> IsGeolocationEnabledAsync()
    {
        Console.WriteLine (String.Format("Avaible on device: {0}", CLLocationManager.LocationServicesEnabled));
        Console.WriteLine (String.Format("Permission on device: {0}", CLLocationManager.Status));

        if (!CLLocationManager.LocationServicesEnabled) {
            tcs.SetResult (false);
        } else if (CLLocationManager.Status == CLAuthorizationStatus.Denied || CLLocationManager.Status == CLAuthorizationStatus.Restricted) {
            tcs.SetResult (false);
        } else if (CLLocationManager.Status == CLAuthorizationStatus.NotDetermined) {

            Console.WriteLine ("Waiting for authorisation");

            CLLocationManager manager = new CLLocationManager ();

            manager.AuthorizationChanged += (object sender, CLAuthorizationChangedEventArgs args) => {

                Console.WriteLine ("Authorization changed to: {0}", args.Status);

                if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                    tcs.SetResult (args.Status == CLAuthorizationStatus.AuthorizedAlways || args.Status == CLAuthorizationStatus.AuthorizedWhenInUse);
                } else {
                    tcs.SetResult (args.Status == CLAuthorizationStatus.Authorized);
                }

                _waitHandle.Set ();
            };

            manager.Failed += (object sender, Foundation.NSErrorEventArgs e) => {

                Console.WriteLine ("Authorization failed");

                tcs.SetResult (false);

                _waitHandle.Set ();
            };

            if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                manager.RequestWhenInUseAuthorization ();
            }

            _waitHandle.WaitOne ();

            Console.WriteLine (String.Format ("Auth complete: {0}", tcs.Task.Result));

        } else {
            if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                tcs.SetResult (CLLocationManager.Status == CLAuthorizationStatus.AuthorizedAlways || CLLocationManager.Status == CLAuthorizationStatus.AuthorizedWhenInUse);
            } else {
                tcs.SetResult (CLLocationManager.Status == CLAuthorizationStatus.Authorized);
            }
        }

        return tcs.Task;
    }
}

公共类位置管理器：ILocationManager
{
静态EventWaitHandle _waitHandle=new AutoResetEvent（false）；
私有TaskCompletionSource tcs=新TaskCompletionSource（）；
公共场所经理（）
{
}
公共任务IsGeolocationEnabledAsync（）
{
Console.WriteLine（String.Format（“在设备上可用：{0}”，CLLocationManager.LocationServicesEnabled））；
Console.WriteLine（String.Format（“设备上的权限：{0}”，CLLocationManager.Status））；
如果（！CLLocationManager.LocationServicesEnabled）{
tcs.SetResult（假）；
}else if（CLLocationManager.Status==CLAuthorizationStatus.Denied | | CLLocationManager.Status==CLAuthorizationStatus.Restricted）{
tcs.SetResult（假）；
}else if（CLLocationManager.Status==CLAuthorizationStatus.NotDetermined）{
Console.WriteLine（“等待授权”）；
CLLocationManager=newcllocationmanager（）；
manager.AuthorizationChanged+=（对象发送方、CLAuthorizationChangedEventArgs）=>{
Console.WriteLine（“授权更改为：{0}”，args.Status）；
if（UIDevice.CurrentDevice.CheckSystemVersion（8,0））{
tcs.SetResult（args.Status==CLAuthorizationStatus.authorizedAllways | | args.Status==CLAuthorizationStatus.AuthorizedWhenInUse）；
}否则{
tcs.SetResult（args.Status==CLAuthorizationStatus.Authorized）；
}
_Set（）；
};
失败的+=（对象发件人，基础.nSerrReErrARGES E）= > {
Console.WriteLine（“授权失败”）；
tcs.SetResult（假）；
_Set（）；
};
if（UIDevice.CurrentDevice.CheckSystemVersion（8,0））{
manager.requestwhenUseAuthorization（）；
}
_waitHandle.WaitOne（）；
Console.WriteLine（String.Format（“Auth complete:{0}”，tcs.Task.Result））；
}否则{
if（UIDevice.CurrentDevice.CheckSystemVersion（8,0））{
tcs.SetResult（CLLocationManager.Status==CLAuthorizationStatus.AuthorizedAlways | | CLLocationManager.Status==CLAuthorizationStatus.AuthorizedWhenInUse）；
}否则{
tcs.SetResult（CLLocationManager.Status==CLAuthorizationStatus.Authorized）；
}
}
返回tcs.Task；
}
}

它工作正常，只是我不明白为什么

manager.AuthorizationChanged

或

manager.Failed

事件似乎永远不会被触发，因此当状态未确定时，线程永远不会释放

非常感谢您的任何帮助或指点。

如果没有这些帮助或指点，您将无法确定问题所在。但是你的代码中肯定有一个明显的设计缺陷，我希望解决这个缺陷能解决你的问题

有什么缺点？你在等待任何事情。您编写了一个显然应该表示异步操作的方法-它的名称中有“Async”，并返回一个

Task

，而不是

bool

-然后您以这样一种方式编写该方法：返回的

Task

将始终完成，而不管采用哪种代码路径

为什么这么糟糕？好的，除了完全无法利用您正在实现的接口的异步方面这一简单事实之外，您正在使用的

CLLocationManager

类很可能希望能够在调用

IsGeolocationEnabledAsync（）

方法的同一线程中运行。由于此方法在引发事件之前不会返回，并且在方法返回之前无法引发事件，因此存在死锁

IMHO，这就是你的类应该如何实现的：

public class LocationManager : ILocationManager
{
    public async Task<bool> IsGeolocationEnabledAsync()
    {
        bool result;

        Console.WriteLine (String.Format("Avaible on device: {0}", CLLocationManager.LocationServicesEnabled));
        Console.WriteLine (String.Format("Permission on device: {0}", CLLocationManager.Status));

        if (!CLLocationManager.LocationServicesEnabled) {
            result = false;
        } else if (CLLocationManager.Status == CLAuthorizationStatus.Denied || CLLocationManager.Status == CLAuthorizationStatus.Restricted) {
            result = false;
        } else if (CLLocationManager.Status == CLAuthorizationStatus.NotDetermined) {
            TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();

            Console.WriteLine ("Waiting for authorisation");

            CLLocationManager manager = new CLLocationManager ();

            manager.AuthorizationChanged += (object sender, CLAuthorizationChangedEventArgs args) => {

                Console.WriteLine ("Authorization changed to: {0}", args.Status);

                if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                    tcs.SetResult (args.Status == CLAuthorizationStatus.AuthorizedAlways || args.Status == CLAuthorizationStatus.AuthorizedWhenInUse);
                } else {
                    tcs.SetResult (args.Status == CLAuthorizationStatus.Authorized);
                }
            };

            manager.Failed += (object sender, Foundation.NSErrorEventArgs e) => {

                Console.WriteLine ("Authorization failed");

                tcs.SetResult (false);
            };

            if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                manager.RequestWhenInUseAuthorization ();
                result = await tcs.Task;
            } else {
                result = false;
            }

            Console.WriteLine (String.Format ("Auth complete: {0}", tcs.Task.Result));

        } else {
            if (UIDevice.CurrentDevice.CheckSystemVersion (8, 0)) {
                result = CLLocationManager.Status == CLAuthorizationStatus.AuthorizedAlways || CLLocationManager.Status == CLAuthorizationStatus.AuthorizedWhenInUse;
            } else {
                result = CLLocationManager.Status == CLAuthorizationStatus.Authorized;
            }
        }

        return result;
    }
}

公共类位置管理器：ILocationManager
{
公共异步任务IsGeolocationEnabledAsync（）
{
布尔结果；
Console.WriteLine（String.Format（“在设备上可用：{0}”，CLLocationManager.LocationServicesEnabled））；
Console.WriteLine（String.Format（“设备上的权限：{0}”，CLLocationManager.Status））；
如果（！CLLocationManager.LocationServicesEnabled）{
结果=假；
}else if（CLLocationManager.Status==CLAuthorizationStatus.Denied | | CLLocationManager.Status==CLAuthorizationStatus.Restricted）{
结果=假；
}else if（CLLocationManager.Status==CLAuthorizationStatus.NotDetermined）{
TaskCompletionSource tcs=新的TaskCompletionSource（）；
Console.WriteLine（“等待授权”）；
CLLocationManager=newcllocationmanager（）；
manager.AuthorizationChanged+=（对象发送方、CLAuthorizationChangedEventArgs）=>{
Console.WriteLine（“授权更改为：{0}”，args.Status）；
if（UIDevice.CurrentDevice.CheckSystemVersion（8,0））{
tcs.SetResult（args.Status==CLAuthorizationStatus.authorizedAllways | | args.Status==CLAuthorizationStatus.AuthorizedWhenInUse）；
}否则{
tcs.SetResult（args.Status==CLAuthorizationStatus.Authorized）；
}
};
失败的+=（对象发件人，基础.nSerrReErrARGES E）= > {
Console.WriteLine（“Auth