Использование кэширования в службе автоматизации пользовательского интерфейса

В этом разделе показано, как реализовать кэширование AutomationElement свойств и шаблонов элементов управления.

Активация запроса кэша

1. Создайте CacheRequest.

2. Укажите свойства и шаблоны для кэширования с помощью Add.

3. Укажите область кэширования, задав свойство TreeScope.

4. Укажите представление поддерев, задав TreeFilter свойство.

5. Установите для свойства AutomationElementMode значение None, если вы хотите повысить эффективность за счет того, что не будете извлекать полные ссылки на объекты. (Это приведет к невозможности получения текущих значений из этих объектов.)

6. Активируйте запрос, используя Activate в using блоке (Using в Microsoft Visual Basic .NET).

После получения AutomationElement объектов или подписки на события деактивируйте запрос с помощью Pop (если Push он использовался) или удалите объект, созданный с помощью Activate. Используйте Activate в блоке using (Using в Microsoft Visual Basic .NET).

Свойства Cache AutomationElement

1. Когда объект CacheRequest активен, получите объекты с помощью AutomationElement или FindFirst, или получите AutomationElement в качестве источника события, зарегистрированного при активности CacheRequest. (Вы также можете создать кэш, передав CacheRequest в метод GetUpdatedCache или один из методов TreeWalker.)

2. Используйте GetCachedPropertyValue или извлеките свойство из свойства Cached объекта AutomationElement.

Получение кэшированных шаблонов и их свойств

1. Хотя CacheRequest активен, получите объекты с помощью FindFirst или FindAll; или получите AutomationElement в качестве источника события, зарегистрированного в то время, когда CacheRequest был активен. (Вы также можете создать кэш, передав CacheRequest в метод GetUpdatedCache или в один из TreeWalker методов.)

2. Используйте GetCachedPattern или TryGetCachedPattern, чтобы извлечь кэшированный шаблон.

3. Извлеките значения из свойств шаблона элемента управления Cached.

Пример 1

В следующем примере кода показаны различные аспекты кэширования, с использованием Activate для активирования CacheRequest.

/// <summary>
/// Caches and retrieves properties for a list item by using CacheRequest.Activate.
/// </summary>
/// <param name="elementList">Element from which to retrieve a child element.</param>
/// <remarks>
/// This code demonstrates various aspects of caching. It is not intended to be
/// an example of a useful method.
/// </remarks>
private void CachePropertiesByActivate(AutomationElement elementList)
{
    AutomationElement elementListItem;

    // Set up the request.
    CacheRequest cacheRequest = new CacheRequest();
    cacheRequest.Add(AutomationElement.NameProperty);
    cacheRequest.Add(AutomationElement.IsEnabledProperty);
    cacheRequest.Add(SelectionItemPattern.Pattern);
    cacheRequest.Add(SelectionItemPattern.SelectionContainerProperty);

    // Obtain an element and cache the requested items.
    using (cacheRequest.Activate())
    {
        Condition cond = new PropertyCondition(AutomationElement.IsSelectionItemPatternAvailableProperty, true);
        elementListItem = elementList.FindFirst(TreeScope.Children, cond);
    }
    // The CacheRequest is now inactive.

    // Retrieve the cached property and pattern.
    SelectionItemPattern pattern;
    String itemName;
    try
    {
        itemName = elementListItem.Cached.Name;
        pattern = elementListItem.GetCachedPattern(SelectionItemPattern.Pattern) as SelectionItemPattern;
    }
    catch (InvalidOperationException)
    {
        Console.WriteLine("Object was not in cache.");
        return;
    }
    // Alternatively, you can use TryGetCachedPattern to retrieve the cached pattern.
    object cachedPattern;
    if (true == elementListItem.TryGetCachedPattern(SelectionItemPattern.Pattern, out cachedPattern))
    {
        pattern = cachedPattern as SelectionItemPattern;
    }

    // Specified pattern properties are also in the cache.
    AutomationElement parentList = pattern.Cached.SelectionContainer;

    // The following line will raise an exception, because the HelpText property was not cached.
    /*** String itemHelp = elementListItem.Cached.HelpText; ***/

    // Similarly, pattern properties that were not specified in the CacheRequest cannot be
    // retrieved from the cache. This would raise an exception.
    /*** bool selected = pattern.Cached.IsSelected; ***/

    // This is still a valid call, even though the property is in the cache.
    // Of course, the cached value and the current value are not guaranteed to be the same.
    itemName = elementListItem.Current.Name;
}

''' <summary>
''' Caches and retrieves properties for a list item by using CacheRequest.Activate.
''' </summary>
''' <param name="elementList">Element from which to retrieve a child element.</param>
''' <remarks>
''' This code demonstrates various aspects of caching. It is not intended to be 
''' an example of a useful method.
''' </remarks>
Private Sub CachePropertiesByActivate(ByVal elementList As AutomationElement)

    ' Set up the request.
    Dim myCacheRequest As New CacheRequest()
    myCacheRequest.Add(AutomationElement.NameProperty)
    myCacheRequest.Add(AutomationElement.IsEnabledProperty)
    myCacheRequest.Add(SelectionItemPattern.Pattern)
    myCacheRequest.Add(SelectionItemPattern.SelectionContainerProperty)

    Dim elementListItem As AutomationElement

    ' Obtain an element and cache the requested items.
    Using myCacheRequest.Activate()
        Dim myCondition As New PropertyCondition( _
            AutomationElement.IsSelectionItemPatternAvailableProperty, True)
        elementListItem = elementList.FindFirst(TreeScope.Children, myCondition)
    End Using


    ' The CacheRequest is now inactive.
    ' Retrieve the cached property and pattern.
    Dim pattern As SelectionItemPattern
    Dim itemName As String
    Try
        itemName = elementListItem.Cached.Name
        pattern = DirectCast(elementListItem.GetCachedPattern(SelectionItemPattern.Pattern), _
            SelectionItemPattern)
    Catch ex As InvalidOperationException
        Console.WriteLine("Object was not in cache.")
        Return
    End Try
    ' Alternatively, you can use TryGetCachedPattern to retrieve the cached pattern.
    Dim cachedPattern As Object = Nothing
    If True = elementListItem.TryGetCachedPattern(SelectionItemPattern.Pattern, cachedPattern) Then
        pattern = DirectCast(cachedPattern, SelectionItemPattern)
    End If

    ' Specified pattern properties are also in the cache.
    Dim parentList As AutomationElement = pattern.Cached.SelectionContainer

    ' The following line will raise an exception, because the HelpText property was not cached.
    '** String itemHelp = elementListItem.Cached.HelpText; **

    ' Similarly, pattern properties that were not specified in the CacheRequest cannot be 
    ' retrieved from the cache. This would raise an exception.
    '** bool selected = pattern.Cached.IsSelected; **

    ' This is still a valid call, even though the property is in the cache.
    ' Of course, the cached value and the current value are not guaranteed to be the same.
    itemName = elementListItem.Current.Name
End Sub

Пример 2

В следующем примере кода показаны различные аспекты кэширования, используя Push для активации CacheRequest. За исключением случаев, когда вы хотите вкладывать запросы в кэш, предпочтительно использовать Activate.

/// <summary>
/// Caches and retrieves properties for a list item by using CacheRequest.Push.
/// </summary>
/// <param name="autoElement">Element from which to retrieve a child element.</param>
/// <remarks>
/// This code demonstrates various aspects of caching. It is not intended to be
/// an example of a useful method.
/// </remarks>
private void CachePropertiesByPush(AutomationElement elementList)
{
    // Set up the request.
    CacheRequest cacheRequest = new CacheRequest();

    // Do not get a full reference to the cached objects, only to their cached properties and patterns.
    cacheRequest.AutomationElementMode = AutomationElementMode.None;

    // Cache all elements, regardless of whether they are control or content elements.
    cacheRequest.TreeFilter = Automation.RawViewCondition;

    // Property and pattern to cache.
    cacheRequest.Add(AutomationElement.NameProperty);
    cacheRequest.Add(SelectionItemPattern.Pattern);

    // Activate the request.
    cacheRequest.Push();

    // Obtain an element and cache the requested items.
    Condition cond = new PropertyCondition(AutomationElement.IsSelectionItemPatternAvailableProperty, true);
    AutomationElement elementListItem = elementList.FindFirst(TreeScope.Children, cond);

    // At this point, you could call another method that creates a CacheRequest and calls Push/Pop.
    // While that method was retrieving automation elements, the CacheRequest set in this method
    // would not be active.

    // Deactivate the request.
    cacheRequest.Pop();

    // Retrieve the cached property and pattern.
    String itemName = elementListItem.Cached.Name;
    SelectionItemPattern pattern = elementListItem.GetCachedPattern(SelectionItemPattern.Pattern) as SelectionItemPattern;

    // The following is an alternative way of retrieving the Name property.
    itemName = elementListItem.GetCachedPropertyValue(AutomationElement.NameProperty) as String;

    // This is yet another way, which returns AutomationElement.NotSupported if the element does
    // not supply a value. If the second parameter is false, a default name is returned.
    object objName = elementListItem.GetCachedPropertyValue(AutomationElement.NameProperty, true);
    if (objName == AutomationElement.NotSupported)
    {
        itemName = "Unknown";
    }
    else
    {
        itemName = objName as String;
    }

    // The following call raises an exception, because only the cached properties are available,
    //  as specified by cacheRequest.AutomationElementMode. If AutomationElementMode had its
    //  default value (Full), this call would be valid.
    /*** bool enabled = elementListItem.Current.IsEnabled; ***/
}

''' <summary>
''' Caches and retrieves properties for a list item by using CacheRequest.Push.
''' </summary>
''' <param name="elementList">Element from which to retrieve a child element.</param>
''' <remarks>
''' This code demonstrates various aspects of caching. It is not intended to be 
''' an example of a useful method.
''' </remarks>
Private Sub CachePropertiesByPush(ByVal elementList As AutomationElement)
    ' Set up the request.
    Dim cacheRequest As New CacheRequest()

    ' Do not get a full reference to the cached objects, only to their cached properties and patterns.
    cacheRequest.AutomationElementMode = AutomationElementMode.None

    ' Cache all elements, regardless of whether they are control or content elements.
    cacheRequest.TreeFilter = Automation.RawViewCondition

    ' Property and pattern to cache.
    cacheRequest.Add(AutomationElement.NameProperty)
    cacheRequest.Add(SelectionItemPattern.Pattern)

    ' Activate the request.
    cacheRequest.Push()

    ' Obtain an element and cache the requested items.
    Dim myCondition As New PropertyCondition(AutomationElement.IsSelectionItemPatternAvailableProperty, _
        True)
    Dim elementListItem As AutomationElement = elementList.FindFirst(TreeScope.Children, myCondition)

    ' At this point, you could call another method that creates a CacheRequest and calls Push/Pop.
    ' While that method was retrieving automation elements, the CacheRequest set in this method 
    ' would not be active. 
    ' Deactivate the request.
    cacheRequest.Pop()

    ' Retrieve the cached property and pattern.
    Dim itemName As String = elementListItem.Cached.Name
    Dim pattern As SelectionItemPattern = _
        DirectCast(elementListItem.GetCachedPattern(SelectionItemPattern.Pattern), SelectionItemPattern)

    ' The following is an alternative way of retrieving the Name property.
    itemName = CStr(elementListItem.GetCachedPropertyValue(AutomationElement.NameProperty))

    ' This is yet another way, which returns AutomationElement.NotSupported if the element does
    ' not supply a value. If the second parameter is false, a default name is returned.
    Dim objName As Object = elementListItem.GetCachedPropertyValue(AutomationElement.NameProperty, True)
    If objName Is AutomationElement.NotSupported Then
        itemName = "Unknown"
    Else
        itemName = CStr(objName)
    End If
    ' The following call raises an exception, because only the cached properties are available, 
    '  as specified by cacheRequest.AutomationElementMode. If AutomationElementMode had its
    '  default value (Full), this call would be valid.
    '** bool enabled = elementListItem.Current.IsEnabled; **

End Sub

См. также

• Кэширование в клиентах автоматизации пользовательского интерфейса