我正在使用 C++/WRL 编写 Windows 10 应用商店/WinRT 代码我是新来的。我很想知道如何取消长期未决的异步操作?
最好的说明方法是用这个例子:
#include <Windows.Services.Store.h>
#include <wrl.h>
auto onAppLicCompletedCallback = Callback<Implements<RuntimeClassFlags<ClassicCom>, IAsyncOperationCompletedHandler<StoreAppLicense*>, FtmBase>>(
[](IAsyncOperation<StoreAppLicense*>* operation, AsyncStatus status)
{
//Asynchronous operation is done
return S_OK;
});
//'opAppLic' is defined as:
// ComPtr<IAsyncOperation<StoreAppLicense*>> opAppLic;
// ...
//Begin asynchronous operation
HRESULT hr = opAppLic->put_Completed(onAppLicCompletedCallback.Get());
if (SUCCEEDED(hr))
{
//Keep going ...
//Say, at some point here I need to cancel 'onAppLicCompletedCallback'
//but how do I do it?
}
编辑:当我尝试按照下面的答案中的建议添加 opAppLic->Cancel()
时,它给了我以下编译器错误:
1>file-name.cpp(597): error C2039: 'Cancel' : is not a member of 'Microsoft::WRL::Details::RemoveIUnknownBase<T>'
1> with
1> [
1> T=ABI::Windows::Foundation::IAsyncOperation<ABI::Windows::Services::Store::StoreAppLicense*>
1> ]
我需要 QueryInterface
代替 IAsyncInfo
还是什么?
EDIT2: 这就是我得到的 opAppLic
变量类型:
不,它没有 Cancel
方法:
最佳答案
IAsyncOperation<TResult>
有一个 Cancel()
方法继承自 IAsyncInfo
.
您无法取消 Completed
处理程序本身。它在异步操作完成时触发。您必须改为取消操作,然后 Completed
处理程序报告操作的最终状态。
#include <Windows.Services.Store.h>
#include <wrl.h>
auto onAppLicCompletedCallback = Callback<Implements<RuntimeClassFlags<ClassicCom>, IAsyncOperationCompletedHandler<StoreAppLicense*>, FtmBase>>(
[](IAsyncOperation<StoreAppLicense*>* operation, AsyncStatus status)
{
//Asynchronous operation is done
if (status == completed)
{
// use results from operation->GetResults() as needed...
}
return S_OK;
});
ComPtr<IAsyncOperation<StoreAppLicense*>> opAppLic;
// Begin asynchronous operation that assigns opAppLic...
opAppLic->put_Completed(onAppLicCompletedCallback.Get());
//Keep going ...
//Say, at some point here I need to cancel the operation...
opAppLic->Cancel();
关于c++ - 如何取消C++/WRL中的异步回调函数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/40201439/