如何:使用 WRL 完成非同步作業
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 應用程式不支援 CRT 函式,以及適用於 UWP 應用程式的 Win32 和 COM。
包含 (
#include
) 任何必要的 Windows 執行階段、Windows 執行階段 C++ 範本連結庫,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 (
#include
) 任何必要的 Windows 執行階段、Windows 執行階段 C++ 範本連結庫,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
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。
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