AutomationPropertyChangedEventHandler 代理人

定義

代表使用者介面自動化用戶端應用程式實作的方法,該方法用來處理使用者介面自動化提供者在屬性已變更時所引發之事件。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)

參數

sender
Object

引發事件的物件。The object that raised the event.

e
AutomationPropertyChangedEventArgs

事件相關資訊。Information about the event.

範例

在下列範例中, IsEnabled 會處理已訂閱專案的屬性變更。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

備註

AutomationElement 表示的 sender 可能不會有任何快取的屬性或模式,這取決於應用程式在作用中時是否訂閱此事件 CacheRequestThe 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.

視提供者的執行而定,屬性變更事件不一定表示屬性值不相同。它可能只表示屬性已設定,甚至是相同的值。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. 如果您的應用程式只需要回應實際變更,您就必須負責追蹤屬性的狀態。If your application needs to respond only to actual changes, it is your responsibility to track the state of the property.

擴充方法

GetMethodInfo(Delegate)

取得表示特定委派所代表之方法的物件。Gets an object that represents the method represented by the specified delegate.

適用於

另請參閱