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我正在尝试获取一个Windows::Devices::Usb::UsbDevice引用我拥有的特定 USB 设备的对象，以便将其传递给第 3 方插件。由于项目限制，我无法使用该C++/CX扩展程序。

在查看了无数线程、答案和参考资料后，我想出了一个初始实现，它使用一些黑魔法来调用我需要的 WinRT 类的静态方法。唯一的问题是，即使没有调用结果为 failed HRESULT，最后一次调用FromIdAsync也不起作用，给我ERROR_INVALID_HANDLE( 6) 作为GetLastError().

简单地阅读错误名称会让我觉得错误在于获取设备的 ID，因为这是我在该调用中传递的唯一句柄，但我尝试传递一个常量字符串（我知道这是正确的）并且它产生了相同的结果。

这就是我调用FromIdAsync* 的方式：

// Retrieves static methods for UsbDevice class
ComPtr<IUsbDeviceStatics> usbDevSt;
hr = GetActivationFactory(
    HStringReference(RuntimeClass_Windows_Devices_Usb_UsbDevice).Get(),
    &usbDevSt
);

// Creates an event to work as a 'semaphore', for waiting for the 'FromIdAsync'
// call to be completed
Event openEvent(CreateEventEx(
    nullptr,
    nullptr,
    CREATE_EVENT_MANUAL_RESET,
    WRITE_OWNER | EVENT_ALL_ACCESS
));
if (!openEvent.IsValid()) return nullptr;

// Setups a callback for when the device enumeration is done
auto asyncOpenCb = Callback<IAsyncOperationCompletedHandler<UsbDevice*>>(
    [&openEvent](IAsyncOperation<UsbDevice*> *opHandler, AsyncStatus status) -> HRESULT {
        if (!opHandler || status != AsyncStatus::Completed) {
            DWORD x = GetLastError(); // ERROR_INVALID_HANDLE (6)
        }

        SetEvent(openEvent.Get());
        return S_OK;
    }
);

// Invokes the 'asyncOpenOp' method, equivalent to UsbDevice::FromIdAsync(String)
ComPtr<IAsyncOperation<UsbDevice*>> asyncOpenOp;
hr = usbDevSt->FromIdAsync(
    devId.Get(),
    asyncOpenOp.GetAddressOf()
);

// Registers completed callback
hr = asyncOpenOp->put_Completed(asyncOpenCb.Get());

// Waits for open operation to complete before continuing
WaitForSingleObjectEx(openEvent.Get(), INFINITE, false);

// Retrieves the result from the asynchronous call
ComPtr<IUsbDevice> dev;
hr = asyncOpenOp->GetResults(dev.GetAddressOf());

这就是我得到devId*的方式：

// Retrieve static methods for DeviceInformation class
ComPtr<IDeviceInformationStatics> devInfoSt;
HRESULT hr = GetActivationFactory(
    HStringReference(RuntimeClass_Windows_Devices_Enumeration_DeviceInformation).Get(),
    &devInfoSt
);

// Create an event to work as a 'semaphore', for waiting for the 'FindAllAsyncAqsFilter' call to be completed
Event findEvent(CreateEventEx(
    nullptr,
    nullptr,
    CREATE_EVENT_MANUAL_RESET,
    WRITE_OWNER | EVENT_ALL_ACCESS
));
if (!findEvent.IsValid()) return nullptr;

// Setup a callback for when the device enumeration is done
auto asyncFindCb = Callback<IAsyncOperationCompletedHandler<DeviceInformationCollection*>>(
    [&findEvent](IAsyncOperation<DeviceInformationCollection*> *opHandler, AsyncStatus status) -> HRESULT {
        SetEvent(findEvent.Get());
        return S_OK;
    }
);

// Invoke the 'FindAllAsyncAqsFilter' method, equivalent to DeviceInformation::FindAllAsync(String)
ComPtr<IAsyncOperation<DeviceInformationCollection*>> asyncFindOp;
hr = devInfoSt->FindAllAsyncAqsFilter(
    HStringReference(DEVICE_FILTER).Get(),
    asyncFindOp.GetAddressOf()
);

// Registers completed callback
hr = asyncFindOp->put_Completed(asyncFindCb.Get());

// Waits for enumeration to complete before continuing
WaitForSingleObjectEx(findEvent.Get(), INFINITE, FALSE);

// Retrieves the result from the asynchronous call
ComPtr<IVectorView<DeviceInformation*>> devColl;
hr = asyncFindOp->GetResults(devColl.GetAddressOf());

// Checks for collection size
unsigned int collSize;
hr = devColl->get_Size(&collSize);

if (collSize == 0) {
    return nullptr;
}

// Retrieves the first DeviceInformation object from the collection
ComPtr<IDeviceInformation> devInfo;
hr = devColl->GetAt(0, devInfo.GetAddressOf());

// Retrieves the device's id
HString devId;
hr = devInfo->get_Id(devId.GetAddressOf());

另外，我确实以这种方式初始化 WinRT：

RoInitializeWrapper initialize(RO_INIT_MULTITHREADED);
if (FAILED(initialize)) return nullptr;

*if (FAILED(hr)) return nullptr;为简洁起见，删除了多个。

4

1 回答 1

0

GetLastError function

检索调用线程的最后一个错误代码值。
最后一个错误代码是在每个线程的基础上维护的。
多个线程不会覆盖彼此的最后一个错误代码。

但我尝试传递一个常量字符串（我知道这是正确的），它产生了相同的结果。

ERROR_INVALID_HANDLE
调用者在 InterfaceHandle 参数中传递了 NULL。

如上所述，您必须从HRESULT

[&openEvent](IAsyncOperation<UsbDevice*> *opHandler, AsyncStatus status) -> HRESULT

我会尝试遍历集合以找出如何从中获取错误

https://msdn.microsoft.com/en-us/library/windows/apps/windows.devices.enumeration.deviceinformationcollection.indexof

于 2016-04-28T12:11:43.790 回答