如何：使用 WRL 完成非同步作業

發行項
11/21/2024

本文件說明如何使用 Windows 執行階段 C++範本庫（WRL）啟動異步操作，並在作業完成時執行工作。

本文件顯示兩個範例。第一個範例會啟動異步定時器，並等候定時器到期。在此範例中，您會在建立定時器物件時指定異步動作。第二個範例會執行背景背景工作線程。此範例示範如何使用傳回IAsyncInfo介面的 Windows 執行階段方法。 Callback 函式是這兩個範例的重要部分，因為它可讓它們指定事件處理程式來處理異步操作的結果。

如需建立元件實例並擷取屬性值的更基本範例，請參閱如何：啟動和使用 Windows 執行階段元件。

提示

這些範例會使用 Lambda 表達式來定義回呼。您也可以使用函式物件（functors）、函式指標或 std：：function 物件。如需C++ Lambda 表達式的詳細資訊，請參閱 Lambda 運算式。

範例：使用定時器

下列步驟會啟動異步定時器，並等候定時器到期。完整的范例如下。

警告

雖然您通常會在通用 Windows 平台（UWP）應用程式中使用 Windows 執行階段 C++範本連結庫，但此範例會使用主控台應用程式來說明。這類 wprintf_s 功能無法從 UWP 應用程式取得。如需您可以在 UWP app 中使用的類型和函式的詳細資訊，請參閱通用 Windows 平台應用程式和適用於 UWP 應用程式的 Win32 和 COM 中不支援的 CRT 函式。

包含（#include）任何必要的 Windows 執行階段、Windows 執行階段 C++範本庫，或C++標準連結庫標頭。

#include <Windows.Foundation.h>
#include <Windows.System.Threading.h>
#include <wrl/event.h>
#include <stdio.h>
#include <Objbase.h>

using namespace ABI::Windows::Foundation;
using namespace ABI::Windows::System::Threading;
using namespace Microsoft::WRL;
using namespace Microsoft::WRL::Wrappers;

Windows.System.Threading.h 宣告使用異步定時器所需的類型。

建議您在 .cpp 檔案中使用 using namespace 指示詞，讓程式代碼更容易閱讀。

初始化 Windows 執行階段。

// Initialize the Windows Runtime.
RoInitializeWrapper initialize(RO_INIT_MULTITHREADED);
if (FAILED(initialize))
{
    return PrintError(__LINE__, initialize);
}

建立介面的 ABI::Windows::System::Threading::IThreadPoolTimer 啟用處理站。

// Get the activation factory for the IThreadPoolTimer interface.
ComPtr<IThreadPoolTimerStatics> timerFactory;
HRESULT hr = GetActivationFactory(HStringReference(RuntimeClass_Windows_System_Threading_ThreadPoolTimer).Get(), &timerFactory);
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

Windows 執行階段會使用完整名稱來識別類型。參數RuntimeClass_Windows_System_Threading_ThreadPoolTimer是 Windows 執行階段所提供的字串，並包含必要的運行時間類別名稱。

建立 Event 物件，將定時器回呼同步處理至主要應用程式。

// Create an event that is set after the timer callback completes. We later use this event to wait for the timer to complete. 
// This event is for demonstration only in a console app. In most apps, you typically don't wait for async operations to complete.
Event timerCompleted(CreateEventEx(nullptr, nullptr, CREATE_EVENT_MANUAL_RESET, WRITE_OWNER | EVENT_ALL_ACCESS));
hr = timerCompleted.IsValid() ? S_OK : HRESULT_FROM_WIN32(GetLastError());
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

注意

此事件僅供作為主控台應用程式的一部分進行示範。此範例會使用事件來確保異步作業在應用程式結束之前完成。在大部分的應用程式中，您通常不會等待異步作業完成。

建立 IThreadPoolTimer 在兩秒后到期的物件。使用函 Callback 式來建立事件處理程式（物件 ABI::Windows::System::Threading::ITimerElapsedHandler ）。

// Create a timer that prints a message after 2 seconds.

TimeSpan delay;
delay.Duration = 20000000; // 2 seconds.

auto callback = Callback<ITimerElapsedHandler>([&timerCompleted](IThreadPoolTimer* timer) -> HRESULT
{
    wprintf_s(L"Timer fired.\n");

    TimeSpan delay;
    HRESULT hr = timer->get_Delay(&delay);
    if (SUCCEEDED(hr))
    {
        wprintf_s(L"Timer duration: %2.2f seconds.\n", delay.Duration / 10000000.0);
    }

    // Set the completion event and return.
    SetEvent(timerCompleted.Get());
    return hr;
});
hr = callback ? S_OK : E_OUTOFMEMORY;
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

ComPtr<IThreadPoolTimer> timer;
hr = timerFactory->CreateTimer(callback.Get(), delay, &timer);
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

將訊息列印至主控台，並等候定時器回呼完成。所有 ComPtr 和RAII對象都會離開範圍，並會自動釋放。

// Print a message and wait for the timer callback to complete.
wprintf_s(L"Timer started.\nWaiting for timer...\n");

// Wait for the timer to complete.
WaitForSingleObjectEx(timerCompleted.Get(), INFINITE, FALSE);
// All smart pointers and RAII objects go out of scope here.

以下是完整的範例：

// wrl-consume-async.cpp
// compile with: runtimeobject.lib
#include <Windows.Foundation.h>
#include <Windows.System.Threading.h>
#include <wrl/event.h>
#include <stdio.h>
#include <Objbase.h>

using namespace ABI::Windows::Foundation;
using namespace ABI::Windows::System::Threading;
using namespace Microsoft::WRL;
using namespace Microsoft::WRL::Wrappers;

// Prints an error string for the provided source code line and HRESULT
// value and returns the HRESULT value as an int.
int PrintError(unsigned int line, HRESULT hr)
{
    wprintf_s(L"ERROR: Line:%d HRESULT: 0x%X\n", line, hr);
    return hr;
}

int wmain()
{
    // Initialize the Windows Runtime.
    RoInitializeWrapper initialize(RO_INIT_MULTITHREADED);
    if (FAILED(initialize))
    {
        return PrintError(__LINE__, initialize);
    }

    // Get the activation factory for the IThreadPoolTimer interface.
    ComPtr<IThreadPoolTimerStatics> timerFactory;
    HRESULT hr = GetActivationFactory(HStringReference(RuntimeClass_Windows_System_Threading_ThreadPoolTimer).Get(), &timerFactory);
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    // Create an event that is set after the timer callback completes. We later use this event to wait for the timer to complete. 
    // This event is for demonstration only in a console app. In most apps, you typically don't wait for async operations to complete.
    Event timerCompleted(CreateEventEx(nullptr, nullptr, CREATE_EVENT_MANUAL_RESET, WRITE_OWNER | EVENT_ALL_ACCESS));
    hr = timerCompleted.IsValid() ? S_OK : HRESULT_FROM_WIN32(GetLastError());
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    // Create a timer that prints a message after 2 seconds.

    TimeSpan delay;
    delay.Duration = 20000000; // 2 seconds.

    auto callback = Callback<ITimerElapsedHandler>([&timerCompleted](IThreadPoolTimer* timer) -> HRESULT
    {
        wprintf_s(L"Timer fired.\n");

        TimeSpan delay;
        HRESULT hr = timer->get_Delay(&delay);
        if (SUCCEEDED(hr))
        {
            wprintf_s(L"Timer duration: %2.2f seconds.\n", delay.Duration / 10000000.0);
        }

        // Set the completion event and return.
        SetEvent(timerCompleted.Get());
        return hr;
    });
    hr = callback ? S_OK : E_OUTOFMEMORY;
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    ComPtr<IThreadPoolTimer> timer;
    hr = timerFactory->CreateTimer(callback.Get(), delay, &timer);
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    // Print a message and wait for the timer callback to complete.
    wprintf_s(L"Timer started.\nWaiting for timer...\n");

    // Wait for the timer to complete.
    WaitForSingleObjectEx(timerCompleted.Get(), INFINITE, FALSE);
    // All smart pointers and RAII objects go out of scope here.
}
/*
Output:
Timer started.
Waiting for timer...
Timer fired.
Timer duration: 2.00 seconds.
*/

編譯程式碼

若要編譯程式代碼，請複製程式代碼，然後將它貼到Visual Studio專案中，或貼到名為 wrl-consume-async.cpp 的檔案中，然後在Visual Studio 命令提示字元視窗中執行下列命令。

cl.exe wrl-consume-async.cpp runtimeobject.lib

範例：使用背景線程

下列步驟會啟動背景工作線程，並定義該線程所執行的動作。完整的范例如下。

提示

此範例示範如何使用 ABI::Windows::Foundation::IAsyncAction 介面。您可以將此模式套用至任何實作 IAsyncInfo的介面： IAsyncAction、 IAsyncActionWithProgress、 IAsyncOperation和 IAsyncOperationWithProgress。

包含任何#include必要的 Windows 執行階段、Windows 執行階段 C++範本庫，或C++標準連結庫標頭。

#include <Windows.Foundation.h>
#include <Windows.System.Threading.h>
#include <wrl/event.h>
#include <stdio.h>
#include <Objbase.h>

using namespace ABI::Windows::Foundation;
using namespace ABI::Windows::System::Threading;
using namespace Microsoft::WRL;
using namespace Microsoft::WRL::Wrappers;

Windows.System.Threading.h 宣告使用背景工作線程所需的類型。

建議您在 .cpp 檔案中使用 using namespace 指示詞，讓程式代碼更容易閱讀。

初始化 Windows 執行階段。

// Initialize the Windows Runtime.
RoInitializeWrapper initialize(RO_INIT_MULTITHREADED);
if (FAILED(initialize))
{
    return PrintError(__LINE__, initialize);
}

建立介面的 ABI::Windows::System::Threading::IThreadPoolStatics 啟用處理站。

// Get the activation factory for the IThreadPoolStatics interface.
ComPtr<IThreadPoolStatics> threadPool;
HRESULT hr = GetActivationFactory(HStringReference(RuntimeClass_Windows_System_Threading_ThreadPool).Get(), &threadPool);
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

建立 Event 物件，將背景工作線程完成同步處理至主要應用程式。

// Create an event that is set after the timer callback completes. We later use this event to wait for the timer to complete. 
// This event is for demonstration only in a console app. In most apps, you typically don't wait for async operations to complete.
Event threadCompleted(CreateEventEx(nullptr, nullptr, CREATE_EVENT_MANUAL_RESET, WRITE_OWNER | EVENT_ALL_ACCESS));
hr = threadCompleted.IsValid() ? S_OK : HRESULT_FROM_WIN32(GetLastError());
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

注意

IThreadPoolStatics::RunAsync呼叫方法來建立背景工作線程。使用函式 Callback 來定義動作。

wprintf_s(L"Starting thread...\n");

// Create a thread that computes prime numbers.
ComPtr<IAsyncAction> asyncAction;
hr = threadPool->RunAsync(Callback<IWorkItemHandler>([&threadCompleted](IAsyncAction* asyncAction) -> HRESULT
{
    // Print a message.
    const unsigned int start = 0;
    const unsigned int end = 100000;
    unsigned int primeCount = 0;
    for (int n = start; n < end; n++)
    {
        if (IsPrime(n))
        {
            primeCount++;
        }
    }

    wprintf_s(L"There are %u prime numbers from %u to %u.\n", primeCount, start, end);

    // Set the completion event and return.
    SetEvent(threadCompleted.Get());
    return S_OK;

}).Get(), &asyncAction);
if (FAILED(hr))
{
    return PrintError(__LINE__, hr);
}

函 IsPrime 式定義於後續的完整範例中。

將訊息列印至主控台，並等候線程完成。所有 ComPtr 和RAII對象都會離開範圍，並會自動釋放。

// Print a message and wait for the thread to complete.
wprintf_s(L"Waiting for thread...\n");

// Wait for the thread to complete.
WaitForSingleObjectEx(threadCompleted.Get(), INFINITE, FALSE);

wprintf_s(L"Finished.\n");

// All smart pointers and RAII objects go out of scope here.

以下是完整的範例：

// wrl-consume-asyncOp.cpp
// compile with: runtimeobject.lib 
#include <Windows.Foundation.h>
#include <Windows.System.Threading.h>
#include <wrl/event.h>
#include <stdio.h>
#include <Objbase.h>

using namespace ABI::Windows::Foundation;
using namespace ABI::Windows::System::Threading;
using namespace Microsoft::WRL;
using namespace Microsoft::WRL::Wrappers;

// Prints an error string for the provided source code line and HRESULT
// value and returns the HRESULT value as an int.
int PrintError(unsigned int line, HRESULT hr)
{
    wprintf_s(L"ERROR: Line:%d HRESULT: 0x%X\n", line, hr);
    return hr;
}

// Determines whether the input value is prime.
bool IsPrime(int n)
{
    if (n < 2)
    {
        return false;
    }
    for (int i = 2; i < n; ++i)
    {
        if ((n % i) == 0)
        {
            return false;
        }
    }
    return true;
}

int wmain()
{
    // Initialize the Windows Runtime.
    RoInitializeWrapper initialize(RO_INIT_MULTITHREADED);
    if (FAILED(initialize))
    {
        return PrintError(__LINE__, initialize);
    }

    // Get the activation factory for the IThreadPoolStatics interface.
    ComPtr<IThreadPoolStatics> threadPool;
    HRESULT hr = GetActivationFactory(HStringReference(RuntimeClass_Windows_System_Threading_ThreadPool).Get(), &threadPool);
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    // Create an event that is set after the timer callback completes. We later use this event to wait for the timer to complete. 
    // This event is for demonstration only in a console app. In most apps, you typically don't wait for async operations to complete.
    Event threadCompleted(CreateEventEx(nullptr, nullptr, CREATE_EVENT_MANUAL_RESET, WRITE_OWNER | EVENT_ALL_ACCESS));
    hr = threadCompleted.IsValid() ? S_OK : HRESULT_FROM_WIN32(GetLastError());
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }


    wprintf_s(L"Starting thread...\n");

    // Create a thread that computes prime numbers.
    ComPtr<IAsyncAction> asyncAction;
    hr = threadPool->RunAsync(Callback<IWorkItemHandler>([&threadCompleted](IAsyncAction* asyncAction) -> HRESULT
    {
        // Print a message.
        const unsigned int start = 0;
        const unsigned int end = 100000;
        unsigned int primeCount = 0;
        for (int n = start; n < end; n++)
        {
            if (IsPrime(n))
            {
                primeCount++;
            }
        }

        wprintf_s(L"There are %u prime numbers from %u to %u.\n", primeCount, start, end);

        // Set the completion event and return.
        SetEvent(threadCompleted.Get());
        return S_OK;

    }).Get(), &asyncAction);
    if (FAILED(hr))
    {
        return PrintError(__LINE__, hr);
    }

    // Print a message and wait for the thread to complete.
    wprintf_s(L"Waiting for thread...\n");

    // Wait for the thread to complete.
    WaitForSingleObjectEx(threadCompleted.Get(), INFINITE, FALSE);

    wprintf_s(L"Finished.\n");

    // All smart pointers and RAII objects go out of scope here.
}
/*
Output:
Starting thread...
Waiting for thread...
There are 9592 prime numbers from 0 to 100000.
Finished.
*/

編譯程式碼

若要編譯程式代碼，請複製程式代碼，然後將它貼到Visual Studio專案中，或貼到名為 wrl-consume-asyncOp.cpp 的檔案中，然後在Visual Studio 命令提示字元視窗中執行下列命令。

cl.exe wrl-consume-asyncOp.cpp runtimeobject.lib

另請參閱

Windows 執行階段 C++ 範本庫 (WRL)

共用方式為

如何：使用 WRL 完成非同步作業

範例：使用定時器

編譯程式碼

範例：使用背景線程

編譯程式碼

另請參閱

意見反應

其他資源