UIElement.ReleasePointerCapture(Pointer) 方法

定義

命名空間:

Windows.UI.Xaml

釋放指標擷取，以供這個 UIElement擷取一個特定指標。

public:
 virtual void ReleasePointerCapture(Pointer ^ value) = ReleasePointerCapture;

void ReleasePointerCapture(Pointer const& value);

public void ReleasePointerCapture(Pointer value);

function releasePointerCapture(value)

Public Sub ReleasePointerCapture (value As Pointer)

參數

value

Pointer

指標參考。 使用先前擷取或指標事件資料的已儲存參考來取得此參考。

範例

此範例示範如何根據處理 PointerReleased呼叫 ReleasePointerCapture。

它也會顯示一開始擷取指標的程式碼，以及追蹤和計算指標參考的模式。

int _pointerCount;

public Scenario2()
{
    this.InitializeComponent();
    bEnteredExited.PointerEntered += bEnteredExited_PointerEntered;
    bEnteredExited.PointerExited += bEnteredExited_PointerExited;
    bEnteredExited.PointerPressed += bEnteredExited_PointerPressed;
    bEnteredExited.PointerReleased += bEnteredExited_PointerReleased;
    bEnteredExited.PointerMoved += bEnteredExited_PointerMoved;

    // To code for multiple Pointers (that is, fingers), 
    // we track how many entered/exited.
    _pointerCount = 0;
}

private void bEnteredExited_PointerMoved(object sender, 
    PointerRoutedEventArgs e)
{
    Scenario2UpdateVisuals(sender as Border, "Moved");
}

private void bEnteredExited_PointerReleased(object sender, 
    PointerRoutedEventArgs e)
{
    ((Border)sender).ReleasePointerCapture(e.Pointer);
    txtCaptureStatus.Text = string.Empty;
}

//Can only get capture on PointerPressed (i.e. touch down, mouse click, pen press)
private void bEnteredExited_PointerPressed(object sender, 
    PointerRoutedEventArgs e)
{
    if (tbPointerCapture.IsOn)
    {
        bool _hasCapture = ((Border)sender).CapturePointer(e.Pointer);
        txtCaptureStatus.Text = "Got Capture: " + _hasCapture;
    }
}

private void bEnteredExited_PointerExited(object sender, 
    PointerRoutedEventArgs e)
{
    _pointerCount--;
    Scenario2UpdateVisuals(sender as Border, "Exited");
}

private void bEnteredExited_PointerEntered(object sender, 
    PointerRoutedEventArgs e)
{
    _pointerCount++;
    Scenario2UpdateVisuals(sender as Border, "Entered");
}

private void Scenario2UpdateVisuals(Border border, 
    String eventDescription)
{
    switch (eventDescription.ToLower())
    {
        case "exited":
            if (_pointerCount <= 0)
            {
                border.Background = new SolidColorBrush(Colors.Red);
                bEnteredExitedTextBlock.Text = eventDescription;
            }
            break;
        case "moved":
            RotateTransform rt = 
                (RotateTransform)bEnteredExitedTimer.RenderTransform;
            rt.Angle += 2;
            if (rt.Angle > 360) rt.Angle -= 360;
            break;
        default:
            border.Background = new SolidColorBrush(Colors.Green);
            bEnteredExitedTextBlock.Text = eventDescription;
            break;
    }
}

private void Scenario2Reset(object sender, RoutedEventArgs e)
{
    Scenario2Reset();
}

private void Scenario2Reset()
{
    bEnteredExited.Background = new SolidColorBrush(Colors.Green);
    bEnteredExitedTextBlock.Text = string.Empty;
}

Private _pointerCount As Integer

Public Sub New()
    Me.InitializeComponent()
    AddHandler bEnteredExited.PointerEntered, AddressOf bEnteredExited_PointerEntered
    AddHandler bEnteredExited.PointerExited, AddressOf bEnteredExited_PointerExited
    AddHandler bEnteredExited.PointerPressed, AddressOf bEnteredExited_PointerPressed
    AddHandler bEnteredExited.PointerReleased, AddressOf bEnteredExited_PointerReleased
    AddHandler bEnteredExited.PointerMoved, AddressOf bEnteredExited_PointerMoved

    'To code for multiple Pointers (i.e. Fingers) we track how many entered/exited.
    _pointerCount = 0
End Sub

''' <summary>
''' Invoked when this page is about to be displayed in a Frame.
''' </summary>
''' <param name="e">Event data that describes how this page was reached.  The Parameter
''' property is typically used to configure the page.</param>
Protected Overrides Sub OnNavigatedTo(e As NavigationEventArgs)
End Sub

Private Sub bEnteredExited_PointerMoved(sender As Object, e As PointerRoutedEventArgs)
    Scenario2UpdateVisuals(TryCast(sender, Border), "Moved")
End Sub

Private Sub bEnteredExited_PointerReleased(sender As Object, e As PointerRoutedEventArgs)
    DirectCast(sender, Border).ReleasePointerCapture(e.Pointer)
    txtCaptureStatus.Text = String.Empty
End Sub

'Can only get capture on PointerPressed (i.e. touch down, mouse click, pen press)
Private Sub bEnteredExited_PointerPressed(sender As Object, e As PointerRoutedEventArgs)
    If tbPointerCapture.IsOn Then
        Dim _hasCapture As Boolean = DirectCast(sender, Border).CapturePointer(e.Pointer)
        txtCaptureStatus.Text = "Got Capture: " & _hasCapture
    End If
End Sub

Private Sub bEnteredExited_PointerExited(sender As Object, e As PointerRoutedEventArgs)
    _pointerCount -= 1
    Scenario2UpdateVisuals(TryCast(sender, Border), "Exited")
End Sub

Private Sub bEnteredExited_PointerEntered(sender As Object, e As PointerRoutedEventArgs)
    _pointerCount += 1
    Scenario2UpdateVisuals(TryCast(sender, Border), "Entered")

End Sub

Private Sub Scenario2UpdateVisuals(border As Border, eventDescription As String)
    Select Case eventDescription.ToLower()
        Case "exited"
            If _pointerCount <= 0 Then
                border.Background = New SolidColorBrush(Colors.Red)
                bEnteredExitedTextBlock.Text = eventDescription
            End If
            Exit Select
        Case "moved"

            Dim rt As RotateTransform = DirectCast(bEnteredExitedTimer.RenderTransform, RotateTransform)
            rt.Angle += 2
            If rt.Angle > 360 Then
                rt.Angle -= 360
            End If
            Exit Select
        Case Else
            border.Background = New SolidColorBrush(Colors.Green)
            bEnteredExitedTextBlock.Text = eventDescription
            Exit Select

    End Select
End Sub

Private Sub Scenario2ResetMethod(sender As Object, e As RoutedEventArgs)
    Reset()
End Sub

Private Sub Reset()
    bEnteredExited.Background = New SolidColorBrush(Colors.Green)
    bEnteredExitedTextBlock.Text = String.Empty
End Sub

備註

以程式設計方式使用 ReleasePointerCapture 釋放指標擷取，不是元素可能會遺失指標擷取的唯一方式。 例如，使用者驅動事件，例如放開指標 (觸控點向上，放開滑鼠按鍵) 可能會導致指標擷取取消。

您可以接聽 PointerCaptureLost事件，以判斷何時發生此情況。

另一個可能會取消指標擷取的方式是，如果指標移出一個應用程式，並在兩個應用程式並存時移至另一個應用程式。

如果您的應用程式程式碼先前稱為 CapturePointer，而且具有您想要釋放指標擷取的特定 Pointer 實例參考，您應該只呼叫 ReleasePointerCapture。 您通常會透過PointerReleased或PointerMoved等事件取得指標參考。

您的應用程式程式碼可能會從具有任何目前指標擷取的不同UIElement呼叫CapturePointer。 如果是，則會取消先前由其他元素建立的任何指標擷取。

UIElement可以擷取多個指標來處理多個觸控點，例如用於操作，但應用程式中只有一個UIElement可以隨時擷取任何指標。 如需詳細資訊，請參閱 處理指標輸入。

另請參閱

• ReleasePointerCaptures()
• CapturePointer(Pointer)
• PointerReleased
• PointerCaptureLost
• 相對滑鼠移動和 CoreWindow
• 輸入範例