UIElement.ReleasePointerCapture(Pointer) 方法
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
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 ReleasePointerCapture
根據處理 PointerReleased呼叫。
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;
}
備註
以程式設計方式釋放指標擷取,不是元素可能會遺失指標擷取 ReleasePointerCapture
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。
只有當您的應用程式程式碼先前稱為CapturePointer,而且具有您要釋放指標擷取的特定Pointer實例參考時,才應該呼叫 ReleasePointerCapture
。 您通常會透過PointerReleased或PointerMoved等事件取得該 Pointer
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
指標可以一次擷取任何指標。 如需詳細資訊,請參閱 處理指標輸入。