AutomationPropertyChangedEventHandler Делегат

Определение

Представляет метод, реализованный в клиентском приложении модели автоматизации пользовательского интерфейса для обработки событий, вызываемых поставщиком модели автоматизации пользовательского интерфейса при изменении свойства.Represents the method implemented by the UI Automation client application to handle the event raised by a UI Automation provider when a property has changed.

public delegate void AutomationPropertyChangedEventHandler(System::Object ^ sender, AutomationPropertyChangedEventArgs ^ e);
public delegate void AutomationPropertyChangedEventHandler(object sender, AutomationPropertyChangedEventArgs e);
type AutomationPropertyChangedEventHandler = delegate of obj * AutomationPropertyChangedEventArgs -> unit
Public Delegate Sub AutomationPropertyChangedEventHandler(sender As Object, e As AutomationPropertyChangedEventArgs)

Параметры

sender
Object

Объект, вызвавший событие.The object that raised the event.

e
AutomationPropertyChangedEventArgs

Сведения о событии.Information about the event.

Наследование
AutomationPropertyChangedEventHandler

Примеры

В следующем примере обрабатываются изменения IsEnabled свойства элементов, на которые оформлена подписка.In the following example, changes in the IsEnabled property of subscribed elements are handled.


AutomationPropertyChangedEventHandler propChangeHandler;
/// <summary>
/// Adds a handler for property-changed event; in particular, a change in the enabled state.
/// </summary>
/// <param name="element">The UI Automation element whose state is being monitored.</param>
public void SubscribePropertyChange(AutomationElement element)
{
    Automation.AddAutomationPropertyChangedEventHandler(element, 
        TreeScope.Element, 
        propChangeHandler = new AutomationPropertyChangedEventHandler(OnPropertyChange),
        AutomationElement.IsEnabledProperty);

}

/// <summary>
/// Handler for property changes.
/// </summary>
/// <param name="src">The source whose properties changed.</param>
/// <param name="e">Event arguments.</param>
private void OnPropertyChange(object src, AutomationPropertyChangedEventArgs e)
{
    AutomationElement sourceElement = src as AutomationElement;
    if (e.Property == AutomationElement.IsEnabledProperty)
    {
        bool enabled = (bool)e.NewValue;
        // TODO: Do something with the new value. 
        // The element that raised the event can be identified by its runtime ID property.
    }
    else
    { 
        // TODO: Handle other property-changed events.
    }
}

public void UnsubscribePropertyChange(AutomationElement element)
{
    if (propChangeHandler != null)
    {
        Automation.RemoveAutomationPropertyChangedEventHandler(element, propChangeHandler);
    }
}

Dim propChangeHandler As AutomationPropertyChangedEventHandler

''' <summary>
''' Adds a handler for property-changed event; in particular, a change in the enabled state.
''' </summary>
''' <param name="element">The UI Automation element whose state is being monitored.</param>
Public Sub SubscribePropertyChange(ByVal element As AutomationElement)
    propChangeHandler = _
        New AutomationPropertyChangedEventHandler(AddressOf OnPropertyChange)
    Automation.AddAutomationPropertyChangedEventHandler(element, TreeScope.Element, _
        propChangeHandler, AutomationElement.IsEnabledProperty)

End Sub



''' <summary>
''' Handler for property changes.
''' </summary>
''' <param name="src">The source whose properties changed.</param>
''' <param name="e">Event arguments.</param>
Private Sub OnPropertyChange(ByVal src As Object, ByVal e As AutomationPropertyChangedEventArgs) 
    Dim sourceElement As AutomationElement = DirectCast(src, AutomationElement)
    If e.Property Is AutomationElement.IsEnabledProperty Then
        Dim enabled As Boolean = CBool(e.NewValue)
        ' TODO: Do something with the new value. 
        ' The element that raised the event can be identified by its runtime ID property.
    Else
    End If
 ' TODO: Handle other property-changed events.
End Sub


Public Sub UnsubscribePropertyChange(ByVal element As AutomationElement)
    If (propChangeHandler IsNot Nothing) Then
        Automation.RemoveAutomationPropertyChangedEventHandler(element, propChangeHandler)
    End If

End Sub

Комментарии

Объект AutomationElement , представленный с помощью sender , может не иметь кэшированных свойств или шаблонов в зависимости от того, подписано ли приложение CacheRequest на это событие, когда оно было активно.The AutomationElement represented by sender might not have any cached properties or patterns, depending on whether the application subscribed to this event while a CacheRequest was active.

В зависимости от реализации поставщика событие изменения свойства не обязательно означает, что значение свойства отличается; Это может означать, что свойство было задано даже для того же значения.Depending on the provider implementation, a property-changed event does not necessarily signify that the property value is different; it might just mean that the property was set, even to the same value. Если приложению нужно ответить только на фактические изменения, вы обязаны следить за состоянием свойства.If your application needs to respond only to actual changes, it is your responsibility to track the state of the property.

Методы расширения

GetMethodInfo(Delegate)

Получает объект, представляющий метод, представленный указанным делегатом.Gets an object that represents the method represented by the specified delegate.

Применяется к

Дополнительно