[ 已針對 Windows 10 上的 UWP 應用程式進行更新。 如需 Windows 8.x 文章，請參閱 存檔。
重要的應用程式介面
瞭解如何將工作專案提交至線程集區，以在個別線程中執行工作。 使用此方法可維護回應式UI，同時仍完成需要明顯時間的工作，並用它來平行完成多個工作。
建立並提交工作專案
呼叫 RunAsync建立工作專案。 提供委派來執行工作（您可以使用 Lambda 或委派函式）。 請注意 ，RunAsync 會傳回 IAsyncAction 物件;儲存此物件以供下一個步驟使用。
有三個版本的 RunAsync 可供使用，以便您可以選擇性地指定工作專案的優先順序，並控制它是否與其他工作專案同時執行。
備註
使用 CoreDispatcher.RunAsync 來存取 UI 線程，並顯示工作項目的進度。
下列範例會建立工作專案，並提供 Lambda 來執行工作：
// The nth prime number to find.
const uint n = 9999;
// Receives the result.
ulong nthPrime = 0;
// Simulates work by searching for the nth prime number. Uses a
// naive algorithm and counts 2 as the first prime number.
IAsyncAction asyncAction = Windows.System.Threading.ThreadPool.RunAsync(
(workItem) =>
{
uint progress = 0; // For progress reporting.
uint primes = 0; // Number of primes found so far.
ulong i = 2; // Number iterator.
if ((n >= 0) && (n <= 2))
{
nthPrime = n;
return;
}
while (primes < (n - 1))
{
if (workItem.Status == AsyncStatus.Canceled)
{
break;
}
// Go to the next number.
i++;
// Check for prime.
bool prime = true;
for (uint j = 2; j < i; ++j)
{
if ((i % j) == 0)
{
prime = false;
break;
}
};
if (prime)
{
// Found another prime number.
primes++;
// Report progress at every 10 percent.
uint temp = progress;
progress = (uint)(10.0*primes/n);
if (progress != temp)
{
String updateString;
updateString = "Progress to " + n + "th prime: "
+ (10 * progress) + "%\n";
// Update the UI thread with the CoreDispatcher.
CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
CoreDispatcherPriority.High,
new DispatchedHandler(() =>
{
UpdateUI(updateString);
}));
}
}
}
// Return the nth prime number.
nthPrime = i;
});
// A reference to the work item is cached so that we can trigger a
// cancellation when the user presses the Cancel button.
m_workItem = asyncAction;
// The nth prime number to find.
const unsigned int n{ 9999 };
// A shared pointer to the result.
// We use a shared pointer to keep the result alive until the
// work is done.
std::shared_ptr<unsigned long> nthPrime = std::make_shared<unsigned long>(0);
// Simulates work by searching for the nth prime number. Uses a
// naive algorithm and counts 2 as the first prime number.
// A reference to the work item is cached so that we can trigger a
// cancellation when the user presses the Cancel button.
m_workItem = Windows::System::Threading::ThreadPool::RunAsync(
[=, strongThis = get_strong()](Windows::Foundation::IAsyncAction const& workItem)
{
unsigned int progress = 0; // For progress reporting.
unsigned int primes = 0; // Number of primes found so far.
unsigned long int i = 2; // Number iterator.
if ((n >= 0) && (n <= 2))
{
*nthPrime = n;
return;
}
while (primes < (n - 1))
{
if (workItem.Status() == Windows::Foundation::AsyncStatus::Canceled)
{
break;
}
// Go to the next number.
i++;
// Check for prime.
bool prime = true;
for (unsigned int j = 2; j < i; ++j)
{
if ((i % j) == 0)
{
prime = false;
break;
}
};
if (prime)
{
// Found another prime number.
primes++;
// Report progress at every 10 percent.
unsigned int temp = progress;
progress = static_cast<unsigned int>(10.f*primes / n);
if (progress != temp)
{
std::wstringstream updateStream;
updateStream << L"Progress to " << n << L"th prime: " << (10 * progress) << std::endl;
std::wstring updateString = updateStream.str();
// Update the UI thread with the CoreDispatcher.
Windows::ApplicationModel::Core::CoreApplication::MainView().CoreWindow().Dispatcher().RunAsync(
Windows::UI::Core::CoreDispatcherPriority::High,
Windows::UI::Core::DispatchedHandler([=]()
{
strongThis->UpdateUI(updateString);
}));
}
}
}
// Return the nth prime number.
*nthPrime = i;
});
// The nth prime number to find.
const unsigned int n = 9999;
// A shared pointer to the result.
// We use a shared pointer to keep the result alive until the
// work is done.
std::shared_ptr<unsigned long> nthPrime = std::make_shared<unsigned long>(0);
// Simulates work by searching for the nth prime number. Uses a
// naive algorithm and counts 2 as the first prime number.
auto workItem = ref new Windows::System::Threading::WorkItemHandler(
[this, n, nthPrime](IAsyncAction^ workItem)
{
unsigned int progress = 0; // For progress reporting.
unsigned int primes = 0; // Number of primes found so far.
unsigned long int i = 2; // Number iterator.
if ((n >= 0) && (n <= 2))
{
*nthPrime = n;
return;
}
while (primes < (n - 1))
{
if (workItem->Status == AsyncStatus::Canceled)
{
break;
}
// Go to the next number.
i++;
// Check for prime.
bool prime = true;
for (unsigned int j = 2; j < i; ++j)
{
if ((i % j) == 0)
{
prime = false;
break;
}
};
if (prime)
{
// Found another prime number.
primes++;
// Report progress at every 10 percent.
unsigned int temp = progress;
progress = static_cast<unsigned int>(10.f*primes / n);
if (progress != temp)
{
String^ updateString;
updateString = "Progress to " + n + "th prime: "
+ (10 * progress).ToString() + "%\n";
// Update the UI thread with the CoreDispatcher.
CoreApplication::MainView->CoreWindow->Dispatcher->RunAsync(
CoreDispatcherPriority::High,
ref new DispatchedHandler([this, updateString]()
{
UpdateUI(updateString);
}));
}
}
}
// Return the nth prime number.
*nthPrime = i;
});
auto asyncAction = ThreadPool::RunAsync(workItem);
// A reference to the work item is cached so that we can trigger a
// cancellation when the user presses the Cancel button.
m_workItem = asyncAction;
在呼叫 RunAsync之後，工作項目會被執行緒集區排入佇列，並在有可用執行緒時運行。 線程集區工作專案會以異步方式執行，而且可以依任何順序執行，因此請確定您的工作專案獨立運作。
請注意，工作專案會檢查 IAsyncInfo.Status 屬性，並在取消工作項目時結束。
處理工作項目完成
藉由設定工作專案的 IAsyncAction.Completed 屬性，提供完成處理程式。 提供委派（可以使用 Lambda 或委派函式）來處理工作項目完成。 例如，使用 CoreDispatcher.RunAsync 來存取 UI 線程並顯示結果。
下列範例會使用步驟 1 中提交的工作項目結果來更新 UI：
asyncAction->Completed = ref new AsyncActionCompletedHandler(
[this, n, nthPrime](IAsyncAction^ asyncInfo, AsyncStatus asyncStatus)
{
if (asyncStatus == AsyncStatus::Canceled)
{
return;
}
String^ updateString;
updateString = "\n" + "The " + n + "th prime number is "
+ (*nthPrime).ToString() + ".\n";
// Update the UI thread with the CoreDispatcher.
CoreApplication::MainView->CoreWindow->Dispatcher->RunAsync(
CoreDispatcherPriority::High,
ref new DispatchedHandler([this, updateString]()
{
UpdateUI(updateString);
}));
});
m_workItem.Completed(
[=, strongThis = get_strong()](Windows::Foundation::IAsyncAction const& asyncInfo, Windows::Foundation::AsyncStatus const& asyncStatus)
{
if (asyncStatus == Windows::Foundation::AsyncStatus::Canceled)
{
return;
}
std::wstringstream updateStream;
updateStream << std::endl << L"The " << n << L"th prime number is " << *nthPrime << std::endl;
std::wstring updateString = updateStream.str();
// Update the UI thread with the CoreDispatcher.
Windows::ApplicationModel::Core::CoreApplication::MainView().CoreWindow().Dispatcher().RunAsync(
Windows::UI::Core::CoreDispatcherPriority::High,
Windows::UI::Core::DispatchedHandler([=]()
{
strongThis->UpdateUI(updateString);
}));
});
asyncAction.Completed = new AsyncActionCompletedHandler(
(IAsyncAction asyncInfo, AsyncStatus asyncStatus) =>
{
if (asyncStatus == AsyncStatus.Canceled)
{
return;
}
String updateString;
updateString = "\n" + "The " + n + "th prime number is "
+ nthPrime + ".\n";
// Update the UI thread with the CoreDispatcher.
CoreApplication.MainView.CoreWindow.Dispatcher.RunAsync(
CoreDispatcherPriority.High,
new DispatchedHandler(()=>
{
UpdateUI(updateString);
}));
});
請注意，完成處理程式會先檢查工作專案是否已取消，在分派 UI 更新之前。
摘要和後續步驟
您可以從 建立適用於 Windows 8.1 的 ThreadPool 工作專案範例 下載本快速入門中的程式碼，並在 win_unap Windows 10 應用程式中重複使用原始程式碼，以深入瞭解。