UIElement.ReleasePointerCapture(Pointer) Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
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)Parameters
- value
- Pointer
The pointer reference. Use either saved references from previous captures, or pointer event data, to obtain this reference.
Examples
This example shows calling ReleasePointerCapture based on handling PointerReleased.
It also shows code for capturing the pointer initially, and a pattern for tracking and counting pointer references.
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
Remarks
Programmatically releasing the pointer capture with ReleasePointerCapture is not the only way that an element might lose pointer capture. For example, user-driven events such as releasing the pointer (touch point up, mouse button released) can cause the pointer capture to be canceled.
You can listen for the PointerCaptureLostevent to determine when this happens.
Another way that pointer capture might be canceled is if a pointer moves out of one app and into another app while the two apps are side-by-side.
You should only call ReleasePointerCapture if your app code has previously called CapturePointer, and has a reference to the particular Pointer instance where you want to release the pointer capture. You'd typically get that Pointer reference through an event such as PointerReleased or perhaps PointerMoved.
Your app code might call CapturePointer from a different UIElement than the one that has any current pointer capture. If so, that cancels any pointer capture previously made by other elements.
A UIElementcan capture multiple pointers to handle multiple touch points such as for manipulations, but only one UIElementin an app can have any pointer captures at any one time. For more info, see Handle pointer input.