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如何使用快取

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本主題包含範例程式碼，示範如何使用 Microsoft 消費者介面自動化 樹狀結構的快取 (或大量擷取) 功能。 它會討論下列主題：

將屬性和控制項模式擷取至快取

下列程式碼範例顯示從清單控制項擷取專案的函式，並快取每個專案的 SelectionItem 控制項模式和 Name 屬性。 根據預設，清單專案會以完整參考傳回，因此所有目前的屬性仍可供使用。

// Given a list element, caches a control pattern and a property for
// all the list items.
IUIAutomationElementArray* FindAndCacheListItems(IUIAutomationElement* pList)
{
    if (pList == NULL)
        return NULL;
    
    IUIAutomationCondition* pCondition = NULL;
    IUIAutomationCacheRequest* pCacheRequest = NULL;
    IUIAutomationElementArray* pFound = NULL;

    HRESULT hr = g_pAutomation->CreateTrueCondition(&pCondition);
    if (FAILED(hr))
        goto cleanup;

    hr = g_pAutomation->CreateCacheRequest(&pCacheRequest);
    if (FAILED(hr))
        goto cleanup;

    hr = pCacheRequest->AddPattern(UIA_SelectionItemPatternId);
    if (FAILED(hr))
        goto cleanup;

    hr = pCacheRequest->AddProperty(UIA_NamePropertyId);
    if (FAILED(hr))
        goto cleanup;

    pList->FindAllBuildCache(TreeScope_Children, pCondition, pCacheRequest, &pFound);
    
cleanup:
    if (pCondition != NULL)
        pCondition->Release();

    if (pCacheRequest != NULL)
        pCacheRequest->Release();

    return pFound;
}

從快取擷取屬性和控制項模式

下列程式碼示範如何從快取擷取屬性和控制模式。 它會擷取清單專案的 SelectionItem 控制項模式和 Name 屬性。

// Demonstrates retrieval of cached properties from a list item
// obtained in FindAndCacheListItems.
HRESULT GetCachedListItem(IUIAutomationElement* pItem)
{           
    if (pItem == NULL)
    {
        return E_INVALIDARG;
    }

    IUIAutomationSelectionItemPattern* pSelectionItemPattern;
    HRESULT hr = pItem->GetCachedPatternAs(UIA_SelectionItemPatternId, 
        IID_IUIAutomationSelectionItemPattern, (void**)&pSelectionItemPattern);
    if (pSelectionItemPattern != NULL)
    {
        // ... To do: Do something with the pattern.

        pSelectionItemPattern->Release();
    }

    // Retrieve a cached property.
    BSTR bstrName;
    hr = pItem->get_CachedName(&bstrName);
    if (SUCCEEDED(hr))
    {
        // ... To do: Do something with the property.

        // Clean up when done with name.
        SysFreeString(bstrName);
        bstrName = NULL;
    }

    BOOL isControl;

    // The following returns E_INVALIDARG because the property was not cached.
    // hr = pItem->get_CachedIsControlElement(&isControl);

    // The following is valid because we have a full reference to the object, therefore
    // we can get current properties. If the cache request had been made with 
    // AutomationElementMode_None, no current properties would be available from
    // this IUIAutomationElement.
    hr = pItem->get_CurrentIsControlElement(&isControl);
    return hr;
}

概念

快取消費者介面自動化屬性和控制模式

消費者介面自動化用戶端的操作說明主題