C++/Cx，可以使用String而不是IAsyncAction调用CreateTask().then

Question

基本上我有下一个函数需要调用异步：

void waitForFrames(){
CMFTWrapper::IsRunning = true;
while (CMFTWrapper::IsRunning){
    result = WaitForSingleObjectEx(CMFTWrapper::FrameEvent, INFINITE, true);
    if (result != WAIT_OBJECT_0){
        // capture aborted, quit. 
    }
    else if (CMFTWrapper::count > 0){
        // copy the bitmap data
    }
}
}

现在我尝试这样做：

create_task(waitForFrames())
    .then([this](task<void> frameTask)
        {
            XTRACE(L"=================================FINISHED WITH FRAME TASKn");
        });

这给了我下一个错误：

Error   26  error C2228: left of '.then' must have class/struct/union   C:UsersAlin RosuWorkspacevidyomobile_windows_phoneVidyo.DeviceManagerWinRTDeviceDetectionLmiVideoCapturerWinRTImplementation.cpp    181 1   Vidyo.DeviceManager
Error   24  error C2784: 'Concurrency::task<_Ty> Concurrency::create_task(const Concurrency::task<_Ty> &)' : could not deduce template argument for 'const Concurrency::task<_Ty> &' from 'void'    C:UsersAlin RosuWorkspacevidyomobile_windows_phoneVidyo.DeviceManagerWinRTDeviceDetectionLmiVideoCapturerWinRTImplementation.cpp    180 1   Vidyo.DeviceManager
Error   25  error C2784: 'Concurrency::task<details::_TaskTypeFromParam<_Ty>::_Type> Concurrency::create_task(_Ty,Concurrency::task_options)' : could not deduce template argument for '_Ty' from 'void'    C:UsersAlin RosuWorkspacevidyomobile_windows_phoneVidyo.DeviceManagerWinRTDeviceDetectionLmiVideoCapturerWinRTImplementation.cpp    180 1   Vidyo.DeviceManager
Error   45  error LNK1104: cannot open file 'C:UsersAlin RosuWorkspacevidyomobile_windows_phoneBuildARMReleaseVidyo.DeviceManagerLmiDeviceManagerWinRT.lib'    C:UsersAlin RosuWorkspacevidyomobile_windows_phoneVidyo.DeviceManager.TestLINK    Vidyo.DeviceManager.Test

现在我尝试将函数的返回值从 void（Dword、int）更改为其他内容，但仍然遇到类似的错误。查看我在网上找到的示例，我找到的所有使用它的函数都返回 IAsyncAction。例：

create_task(m_pMediaCapture->StartRecordToStorageFileAsync(m_EncodingProfile, m_recordStorageFile))
                    .then([this](task<void> recordTask)
                {
                    XTRACE(L"=================================will try to get record taskn");
}

如何使用我的正常函数执行此操作，以便它可以异步运行？

Answer 1

您可以将 lambda 直接传递给 create_task 函数：

create_task( [](){ /* code here */ } ) .

因此，在您的方案中，以下内容应该有效：

create_task([](){ waitForFrames(); })
.then([this](task<void> frameTask){
            XTRACE(L"=================================FINISHED WITH FRAME TASKn");
});