使用C ++ WRL打开UsbDevice - ERROR_INVALID_HANDLE

Question

我正在尝试获取引用我所拥有的特定USB设备的Windows::Devices::Usb::UsbDevice对象，以便将其传递给第三方插件。由于项目限制，我无法使用C++/CX扩展名。

在查看了无数的线程，答案和引用之后，我想出了一个初始实现，它可以在我需要的WinRT类上调用静态方法。唯一的问题是，即使没有通话导致失败的HRESULT，最后一次调用FromIdAsync也不起作用，因此给我ERROR_INVALID_HANDLE（6） GetLastError()。

简单地读取错误名称会让我误认为是获取设备的ID，因为这是我传递给该调用的唯一句柄，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 *：

的方法

// 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，我这样做初始化WinRT：

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

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

Answer 1

<强> GetLastError function

  

检索调用线程的最后错误代码值   最后一个错误代码基于每个线程维护   多个线程不会相互覆盖最后一个错误代码。

  

但我尝试传递一个常量字符串（我知道这是正确的）并且它产生了相同的结果。

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

如上所述，您必须从HRESULT

获得结果

[&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