usb - 如何在 Windows 10 通用应用程序中使用键盘支持从磁条阅读器读取输入流

Question

我们已经尝试了建议的方法:

https://msdn.microsoft.com/en-us/library/windows/hardware/dn312121(v=vs.85).aspx https://msdn.microsoft.com/en-us/library/windows/hardware/dn303343(v=vs.85).aspx

我们可以使用下面的代码片段找出所有磁性设备的列表

var magneticDevices = await DeviceInformation.FindAllAsync(aqsFilter);

但是我们无法从下面的代码中获取 HidDevice 对象。它给出空值。

HidDevice device = await HidDevice.FromIdAsync(magneticDevices[0].Id

我们还在应用 list 文件中设置了设备功能，如下所示。

<DeviceCapability Name="humaninterfacedevice">
    <Device Id="vidpid:0ACD 0520">
      <Function Type="usage:0001 0006"/>
    </Device>
</DeviceCapability>

<DeviceCapability Name="usb">
    <Device Id="vidpid:0ACD 0520">
      <Function Type="winUsbId:4d1e55b2-f16f-11cf-88cb-001111000030"/>
    </Device>
</DeviceCapability>

完整函数的代码

 private async Task<bool> HasCardReader()
        {
            bool hasCardReader = false;
            ushort usagePage = 0x0001;
            ushort usageId = 0x0006;
            ushort vendorId = 0x0ACD;
            ushort productId = 0x0520;
            var aqsFilter = HidDevice.GetDeviceSelector(usagePage, usageId, vendorId, productId);
            var magneticDevices = await DeviceInformation.FindAllAsync(aqsFilter);
            try
            {
                if (magneticDevices != null && magneticDevices.Count > 0)
                {
                    HidDevice device = await HidDevice.FromIdAsync(magneticDevices[0].Id, Windows.Storage.FileAccessMode.Read);
                    inputReportEventHandler = new TypedEventHandler<HidDevice, HidInputReportReceivedEventArgs>(this.OnInputReportEvent);
                    device.InputReportReceived += inputReportEventHandler;
                    var watcher = DeviceInformation.CreateWatcher(aqsFilter);
                    watcher.Added += WatcherAdded;
                    watcher.Removed += WatcherRemoved;
                    watcher.Start();
                    hasCardReader = true;
            }
                else
                {

                }
            }
            catch (Exception ex)
            {
                Logging.LoggingSessionScenario.LogMessageAsync(ex.Message, LoggingLevel.Error);
            }
            return hasCardReader;
            }

Answer 1

空返回值有多种原因，但我认为您的代码没有问题，因为您可以通过调用 FindAllAsync 找到设备。我建议您使用 this official HIDDevice sample 解决此问题在 GitHub 上。

通过将 vid & pid & usagepage & usageid 更改为我的设备，我使用该示例成功连接到我的外部 hid 设备。

在EventHandlerForDevice.cs中，找到函数OpenDeviceAsync，当FromIdAsync返回null时，你会注意到以下可能的原因。

else
{
    successfullyOpenedDevice = false;

    notificationStatus = NotifyType.ErrorMessage;

    var deviceAccessStatus = DeviceAccessInformation.CreateFromId(deviceInfo.Id).CurrentStatus;

    if (deviceAccessStatus == DeviceAccessStatus.DeniedByUser)
    {
        notificationMessage = "Access to the device was blocked by the user : " + deviceInfo.Id;
    }
    else if (deviceAccessStatus == DeviceAccessStatus.DeniedBySystem)
    {
        // This status is most likely caused by app permissions (did not declare the device in the app's package.appxmanifest)
        // This status does not cover the case where the device is already opened by another app.
        notificationMessage = "Access to the device was blocked by the system : " + deviceInfo.Id;
    }
    else
    {
        // Most likely the device is opened by another app, but cannot be sure
        notificationMessage = "Unknown error, possibly opened by another app : " + deviceInfo.Id;
    }
}

尝试使用该示例 (Scenario1) 并更改 appxmanifest 和 SampleConfiguration.cs(class Device) 中的 ID。如果您在设备列表中看不到您的设备，则表示您的设备配置不正确。