AutomationElement.GetCachedPropertyValue 方法
定义
重要
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从 AutomationElement 检索指定属性的缓存值。
重载
GetCachedPropertyValue(AutomationProperty) |
从此 AutomationElement 的缓存中检索指定属性的值。 对于目标用户界面 (UI) 元素未显式支持的属性,将返回属性类型的相应默认值。 |
GetCachedPropertyValue(AutomationProperty, Boolean) |
从此 AutomationElement 的缓存中检索指定属性的值,还可以选择忽略任何默认属性。 |
注解
GetCachedPropertyValue 从 的 AutomationElement缓存中检索指定的属性。 若要检索当前属性,请调用 GetCurrentPropertyValue。
GetCachedPropertyValue(AutomationProperty)
从此 AutomationElement 的缓存中检索指定属性的值。 对于目标用户界面 (UI) 元素未显式支持的属性,将返回属性类型的相应默认值。
public:
System::Object ^ GetCachedPropertyValue(System::Windows::Automation::AutomationProperty ^ property);
public object GetCachedPropertyValue (System.Windows.Automation.AutomationProperty property);
member this.GetCachedPropertyValue : System.Windows.Automation.AutomationProperty -> obj
Public Function GetCachedPropertyValue (property As AutomationProperty) As Object
参数
- property
- AutomationProperty
要检索的属性的标识符。
返回
一个包含指定属性的值的对象。
例外
请求的属性不在缓存中。
的用户界面 (UI) AutomationElement 不再存在。
示例
下面演示如何使用此方法检索缓存的属性。
/// <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
注解
如果元素本身的 UI 自动化提供程序支持 属性,则返回 属性的值。 否则,将返回由 UI 自动化指定的默认属性。 有关默认属性的信息,请参阅 的属性 AutomationElement标识符字段,例如 AcceleratorKeyProperty。
GetCachedPropertyValue 从 AutomationElement的缓存中检索指定的属性。 若要检索指定属性的当前对象,请调用 GetCurrentPropertyValue。
如果以前未缓存请求的属性,此方法将引发异常。
适用于
GetCachedPropertyValue(AutomationProperty, Boolean)
从此 AutomationElement 的缓存中检索指定属性的值,还可以选择忽略任何默认属性。
public:
System::Object ^ GetCachedPropertyValue(System::Windows::Automation::AutomationProperty ^ property, bool ignoreDefaultValue);
public object GetCachedPropertyValue (System.Windows.Automation.AutomationProperty property, bool ignoreDefaultValue);
member this.GetCachedPropertyValue : System.Windows.Automation.AutomationProperty * bool -> obj
Public Function GetCachedPropertyValue (property As AutomationProperty, ignoreDefaultValue As Boolean) As Object
参数
- property
- AutomationProperty
要检索的属性的标识符。
- ignoreDefaultValue
- Boolean
一个值,该值指定如果不支持指定的属性,是否应忽略默认值。
返回
一个包含指定属性的值的对象,如果该元素未提供值并且 NotSupported 为 ignoreDefaultValue
,则为 true
。
例外
请求的属性不在缓存中。
AutomationElement 的 UI 不再存在。
示例
以下示例演示如何使用此方法检索缓存的属性。
/// <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
注解
GetCachedPropertyValue 从 的缓存 AutomationElement中检索指定的属性。 若要检索当前属性,请调用 GetCurrentPropertyValue。
传入 false
ignoreDefaultValue
等效于调用 AutomationElement.GetCachedPropertyValue(AutomationProperty)。
如果元素本身的 UI 自动化提供程序支持 属性,则返回 属性的值。 否则,如果 ignoreDefaultValue
为 false
,则返回由 UI 自动化指定的默认属性。 有关默认属性的信息,请参阅 的属性 AutomationElement标识符字段,例如 AcceleratorKeyProperty。
如果以前未缓存请求的属性,此方法将引发异常。