How to Retrieve a Virtualized Item

This topic contains example code that shows how to find and retrieve UI information about virtualized items in a control.

The following example searches a container for an item that has the specified name and retrieves the IUIAutomationElement interface for the item. The example looks in the UI Automation subtree first. If the item is not there, the example uses the container IUIAutomationItemContainerPattern interface to find the item, and then uses the item IUIAutomationVirtualizedItemPattern interface to realize the item.

HRESULT GetContainerItem (BSTR bstrItemName, IUIAutomationElement *pContainerElement, 
                          IUIAutomationElement **ppItemElement)                                  
{
    HRESULT hr;
    VARIANT varNameStr;
    IUIAutomationCondition *pNamePropertyCond = NULL;
    IUIAutomationElement *pFoundElement = NULL;
    IUIAutomationItemContainerPattern *pItemContainer = NULL;

    // Make sure the pointers are valid.
    if (ppItemElement == NULL || pContainerElement == NULL || bstrItemName == NULL)
        return E_INVALIDARG;
    
    *ppItemElement = NULL;

    // Try to find the item in the UI Automation tree. This attempt will fail if the
    // item is virtualized. Note: g_pAutomation is a global pointer to the IUIAutomation interface.
    varNameStr.vt = VT_BSTR;
    varNameStr.bstrVal = SysAllocString(bstrItemName);
    hr = g_pAutomation->CreatePropertyCondition(UIA_NamePropertyId, varNameStr, &pNamePropertyCond);
    if (pNamePropertyCond == NULL)
        goto cleanup;

    hr = pContainerElement->FindFirst(TreeScope_Subtree, pNamePropertyCond, &pFoundElement);
    if (pFoundElement == NULL) { 

        // The item is not in the UI Automation tree, so it may be virtualized. Try
        // using the ItemContainer control pattern to find the item.
        hr = pContainerElement->GetCurrentPatternAs(UIA_ItemContainerPatternId, 
                                                    __uuidof(IUIAutomationItemContainerPattern), 
                                                    (void**)&pItemContainer);
        if (pItemContainer == NULL)
            goto cleanup;

        hr = pItemContainer->FindItemByProperty(NULL, UIA_NamePropertyId, varNameStr, &pFoundElement);
        if (pFoundElement == NULL) // container has no item with the specified name
            goto cleanup;
    }

    // Attempt to get the name property. The attempt will fail with 
    // UIA_E_ELEMENTNOTAVAILABLE if the item is virtualized. 
    BSTR bstrName; 
    hr = pFoundElement->get_CurrentName(&bstrName);
    if (hr == UIA_E_ELEMENTNOTAVAILABLE) 
    {
        // The item might be virtualized. Use the VirtualizedItem control pattern to 
        // realize the item. 
        IUIAutomationVirtualizedItemPattern *pVirtualizedItem;
        hr = pFoundElement->GetCurrentPatternAs(UIA_VirtualizedItemPatternId, 
                    __uuidof(IUIAutomationVirtualizedItemPattern), (void**)&pVirtualizedItem);
        if (pVirtualizedItem == NULL)
            goto cleanup;

        hr = pVirtualizedItem->Realize();
        pVirtualizedItem->Release();

        if (hr != S_OK)
            goto cleanup;

        // Try to get the name again. 
        hr = pFoundElement->get_CurrentName(&bstrName);
    }    

    if (SUCCEEDED(hr))
    {
        // Make sure the item is the one we're looking for.
        if (wcscmp(bstrName, bstrItemName) == 0)
        {
            *ppItemElement = pFoundElement;
            pFoundElement = NULL;
        }
    }


cleanup:
        VariantClear(&varNameStr);

        if (pNamePropertyCond != NULL) pNamePropertyCond->Release();
        if (pFoundElement != NULL) pFoundElement->Release();
        if (pItemContainer != NULL) pItemContainer->Release();

        return hr;
}

Related topics

Conceptual

Working with Virtualized Items

How-To Topics for UI Automation Clients