为什么 UI 自动化条件无法通过 UIA_IsScrollPatternAvailablePropertyId 找到元素？

Question

我想在允许滚动的主窗口句柄中找到元素。因此，我不想找到滚动条，然后是滚动条的所有者，我只想返回允许通过 ScrollPattern 滚动的项目，所以我设置了条件，但什么也没找到。如果我搜索滚动条所有者窗口，然后获取 ScrollPattern 它可以工作。为什么我不能只找到具有可用滚动模式的元素？

这是通用代码：

BOOL CUIAutomateScroller::FindWindow(HWND hwnd, IUIAutomationElement **windowelement)
{
  BOOL result=FALSE;
  // make sure init completed
  if (m_pClientUIA) {
    // get window element
    HRESULT hr=m_pClientUIA->ElementFromHandle(hwnd, windowelement);
    // check result
    result=SUCCEEDED(hr);
    // output debug info
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("ElementFromHandle error: %d\n"), hr);
    }
    else {
      _ASSERT(*windowelement!=NULL);
    }
  }
  return result;
}

BOOL CUIAutomateScroller::FindContainerWindowElement(const long controltype, IUIAutomationElement **pelement)
{
  // Create search condition
  VARIANT varprop;
  varprop.vt=VT_I4;
  varprop.uintVal=controltype;

  CComPtr<IUIAutomationCondition> pcondition;
  HRESULT hr=m_pClientUIA->CreatePropertyCondition(UIA_ControlTypePropertyId, varprop, &pcondition);
  if (FAILED(hr)) {
    CDebugPrint::DebugPrint(_T("CreatePropertyCondition error: %d\n"), hr);
    return NULL;
  }

  // find the control based on condition
  CComPtr<IUIAutomationElementArray> pcontrolelementarr;
  hr=m_pWindowElement->FindAll(TreeScope_Subtree, pcondition, &pcontrolelementarr);
  if (FAILED(hr)) {
    CDebugPrint::DebugPrint(_T("CreatePropertyCondition error: %d\n"), hr);
    return NULL;
  }

  // get number of controls found
  int numfound;
  pcontrolelementarr->get_Length(&numfound);
  CDebugPrint::DebugPrint(_T("Controls Found: %d\n"), numfound);

  // process controls found, but really we exit earily if container window found
  for (int i=0; i < numfound; i++) {
    // get individual control element
    CComPtr<IUIAutomationElement> pcontrolelement;
    hr=pcontrolelementarr->GetElement(i, &pcontrolelement);
    if (FAILED(hr)) {
      // skip element unable to be retreived
      CDebugPrint::DebugPrint(_T("GetElement error: %d\n"), hr);
      continue;
    }

    // output debug information
    CComBSTR name;
    hr=pcontrolelement->get_CurrentName(&name);
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("GetCurrentName error: %d\n"), hr);
    }
    CDebugPrint::DebugPrint(_T("Control Name: %s\n"), name);
    name.Empty();

    hr=pcontrolelement->get_CurrentClassName(&name);
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("GetCurrentClass error: %d\n"), hr);
    }
    CDebugPrint::DebugPrint(_T("Class Name: %s\n"), name);
    name.Empty();

    CComPtr<IUIAutomationTreeWalker> pcontentwalker=NULL;
    hr=m_pClientUIA->get_ContentViewWalker(&pcontentwalker);
    if (pcontentwalker == NULL) {
      return NULL;
    }

    // Get ancestor element nearest to the scrollbar UI Automation element in the tree view
    hr=pcontentwalker->NormalizeElement(pcontrolelement, pelement);
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("NormalizeElement error: %d\n"), hr);
      return NULL;
    }

    // output debug information
    hr=(*pelement)->get_CurrentName(&name);
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("get_CurrentName error: %d\n"), hr);
    }
    CDebugPrint::DebugPrint(_T("Ancestor Name: %s\n"), name);
    name.Empty();

    return TRUE;
  }

  return FALSE;
}

这不起作用（它没有找到任何东西）：

  // get main window
  if (FindWindow(hwnd, &m_pWindowElement)) {
    HRESULT hr;
    VARIANT varprop;
      
    // create condition for elements that have UIA_IsScrollPatternAvailablePropertyId available
    CComPtr<IUIAutomationCondition> pscrollpatterncondition;
    varprop.vt=VT_BOOL;
    varprop.boolVal=TRUE;
    hr=m_pClientUIA->CreatePropertyCondition(UIA_IsScrollPatternAvailablePropertyId, varprop, &pscrollpatterncondition);
    // check result
    if (FAILED(hr)) {
      CDebugPrint::DebugPrint(_T("CreatePropertyCondition for ScrollPattern Error: %d\n"), hr);
    }
    else {
      // find the matching element
      CComPtr<IUIAutomationElementArray> pscrollpatternarr;
      hr=m_pWindowElement->FindAll(TreeScope_Subtree, pscrollpatterncondition, &pscrollpatternarr);
      // check result (normal is success with empty array if not found)
      if (FAILED(hr)) {
        CDebugPrint::DebugPrint(_T("FindAll Error: %d\n"), hr);
      }
      else {
        // get number of elements in array
        int numfound=0;
        pscrollpatternarr->get_Length(&numfound);
        // make sure we only get one scrollable area - in the future we could figure out the rect
        // **numfound is 0**

这确实有效：

  // get main window
  if (FindWindow(hwnd, &m_pWindowElement)) {
    // get scrollable window element based on scrollbar
    if (FindContainerWindowElement(UIA_ScrollBarControlTypeId, &m_pScrollableElement)) {
      HRESULT hr;
      // get the scroll pattern
      hr=m_pScrollableElement->GetCurrentPattern(UIA_ScrollPatternId, (IUnknown**) &m_pScrollPattern);
      if (FAILED(hr)) {
        CDebugPrint::DebugPrint(_T("GetCurrentPattern for Scroll Pattern Error %d:\n"), hr);
      }
      else if (m_pScrollPattern!=NULL) {
        // **we're good!!**

Answer 1

为什么我不能只找到具有滚动模式的元素 可用吗？

正如@HansPassant 指出的那样，使用VARIANT_TRUE (-1) 而不是TRUE (1)。

在更正上述错误后，以下代码适用于我查找具有可用滚动模式 (IUIAutomationScrollPattern) 和 scrolling（垂直滚动条）的元素。

    VARIANT varprop;

    // create condition for elements that have UIA_IsScrollPatternAvailablePropertyId available
    CComPtr<IUIAutomationCondition> pscrollpatterncondition;
    varprop.vt = VT_BOOL;
    varprop.boolVal = VARIANT_TRUE;
    hr = m_pClientUIA->CreatePropertyCondition(UIA_IsScrollPatternAvailablePropertyId, varprop, &pscrollpatterncondition);
    // check result
    if (FAILED(hr)) {
    }
    else {
        // find the matching element
        CComPtr<IUIAutomationElementArray> pscrollpatternarr;
        hr = m_pWindowElement->FindAll(TreeScope_Subtree, pscrollpatterncondition, &pscrollpatternarr);
        // check result (normal is success with empty array if not found)
        if (FAILED(hr)) {
        }
        else {
            // get number of elements in array
            numfound = 0;
            pscrollpatternarr->get_Length(&numfound);
            for (int i = 0; i < numfound; i++)
            {
                IUIAutomationElement *element = NULL;
                pscrollpatternarr->GetElement(i, &element);

                IUIAutomationScrollPattern  *m_pScrollPattern = NULL;
                hr = element->GetCurrentPattern(UIA_ScrollPatternId, (IUnknown**)&m_pScrollPattern);
                if (FAILED(hr)) {
                }
                else if (m_pScrollPattern != NULL) {
                    // Scroll vertical scrollbar
                    m_pScrollPattern->Scroll(ScrollAmount_NoAmount, ScrollAmount_LargeIncrement);
                }
            }
        }
    }