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如何浏览 UI 自动化树

  • 项目

本主题包含演示如何使用 IUIAutomationTreeWalker 接口演练和检查 Microsoft UI 自动化树中的元素的示例代码。 讨论以下主题：

遍历元素的子代

下面的代码示例是一个递归函数，它遍历 UI 元素的所有子代，并在分层列表中显示其控件类型。

// CAUTION: Do not pass in the root (desktop) element. Traversing the entire subtree
// of the desktop could take a very long time and even lead to a stack overflow.
void ListDescendants(IUIAutomationElement* pParent, int indent)
{
    if (pParent == NULL)
        return;

    IUIAutomationTreeWalker* pControlWalker = NULL;
    IUIAutomationElement* pNode = NULL;

    g_pAutomation->get_ControlViewWalker(&pControlWalker);
    if (pControlWalker == NULL)
        goto cleanup;

    pControlWalker->GetFirstChildElement(pParent, &pNode);
    if (pNode == NULL)
        goto cleanup;

    while (pNode)
    {
        BSTR desc;
        pNode->get_CurrentLocalizedControlType(&desc);
        for (int x = 0; x <= indent; x++)
        {
            std::wcout << L"   ";
        }
        std::wcout << desc << L"\n";
        SysFreeString(desc);

        ListDescendants(pNode, indent+1);
        IUIAutomationElement* pNext;
        pControlWalker->GetNextSiblingElement(pNode, &pNext);
        pNode->Release();
        pNode = pNext;
    }

cleanup:
    if (pControlWalker != NULL)
        pControlWalker->Release();

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

    return;
}

遍历上级元素

下面的代码示例是一个函数，它遍历元素的上级以标识父元素。 当你需要标识控件的父窗口时，这非常有用。 该函数为顶级元素返回 NULL；即父元素为桌面的元素。

IUIAutomationElement* GetContainingWindow(IUIAutomationElement* pChild)
{

    if (pChild == NULL)
        return NULL;

    IUIAutomationElement* pDesktop = NULL;
    HRESULT hr = g_pAutomation->GetRootElement(&pDesktop);
    if (FAILED(hr))
        return NULL;

    BOOL same;
    g_pAutomation->CompareElements(pChild, pDesktop, &same);
    if (same)
    {
        pDesktop->Release();
        return NULL; // No parent, so return NULL.
    }

    IUIAutomationElement* pParent = NULL;
    IUIAutomationElement* pNode = pChild;

    // Create the treewalker.
    IUIAutomationTreeWalker* pWalker = NULL;
    g_pAutomation->get_ControlViewWalker(&pWalker);
    if (pWalker == NULL)
        goto cleanup;

    // Walk up the tree.
    while (TRUE)
    {
        hr = pWalker->GetParentElement(pNode, &pParent);
        if (FAILED(hr) || pParent == NULL)
        {
            break;
        }
        g_pAutomation->CompareElements(pParent, pDesktop, &same);
        if (same)
        {
            pDesktop->Release();
            pParent->Release();
            pWalker->Release();
            // Reached desktop, so return next element below it.
            return pNode;
        }
        if (pNode != pChild) // Do not release the in-param.
            pNode->Release();
        pNode = pParent;
    }

cleanup:
    if ((pNode != NULL) && (pNode != pChild)) 
        pNode->Release();

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

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

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

    return NULL;  
}

Conceptual

获取 UI 自动化元素

UI 自动化客户端的操作指南主题