TouchFrameEventArgs.GetPrimaryTouchPoint(IInputElement) 方法

public:
 System::Windows::Input::TouchPoint ^ GetPrimaryTouchPoint(System::Windows::IInputElement ^ relativeTo);

public System.Windows.Input.TouchPoint GetPrimaryTouchPoint(System.Windows.IInputElement relativeTo);

member this.GetPrimaryTouchPoint : System.Windows.IInputElement -> System.Windows.Input.TouchPoint

Public Function GetPrimaryTouchPoint (relativeTo As IInputElement) As TouchPoint

參數

傳回

主節點 TouchDevice 相對於指定元件的當前位置;或 null 是主節點 TouchDevice 未啟用時。

範例

以下程式碼處理從 TouchFrameEventArgs中擷取的觸點。 當在 上按下 Canvas時，會 TouchDevice 被捕捉到 Canvas。 當觸感被抬起時，就會釋放。TouchDevice 當觸控移動到 Canvas時 Id ，會被檢查。 若 與 Id 主要接觸點的 相 Id 符，表示首次觸碰，則會記錄其位置。 若移動來自第二次觸球，則會從第一次觸球的位置畫一條線到第二次觸球的位置。

這個範例是類別概述中另一個較大範例 Touch 的一部分。

foreach (TouchPoint _touchPoint in e.GetTouchPoints(this.canvas1))
{
    if (_touchPoint.Action == TouchAction.Down)
    {
        // Clear the canvas and capture the touch to it.
        this.canvas1.Children.Clear();
        _touchPoint.TouchDevice.Capture(this.canvas1);
    }

    else if (_touchPoint.Action == TouchAction.Move && e.GetPrimaryTouchPoint(this.canvas1) != null)
    {   
        // This is the first (primary) touch point. Just record its position.
        if (_touchPoint.TouchDevice.Id == e.GetPrimaryTouchPoint(this.canvas1).TouchDevice.Id)
        {
            pt1.X = _touchPoint.Position.X;
            pt1.Y = _touchPoint.Position.Y;
        }

        // This is not the first touch point. Draw a line from the first point to this one.
        else if (_touchPoint.TouchDevice.Id != e.GetPrimaryTouchPoint(this.canvas1).TouchDevice.Id)
        {
            pt2.X = _touchPoint.Position.X;
            pt2.Y = _touchPoint.Position.Y;

            Line _line = new Line();
            _line.Stroke = new RadialGradientBrush(Colors.White, Colors.Black);
            _line.X1 = pt1.X;
            _line.X2 = pt2.X;
            _line.Y1 = pt1.Y;
            _line.Y2 = pt2.Y;
            _line.StrokeThickness = 2;
            this.canvas1.Children.Add(_line);
        }
    }

    else if (_touchPoint.Action == TouchAction.Up)
    {
        // If this touch is captured to the canvas, release it.
        if (_touchPoint.TouchDevice.Captured == this.canvas1)
        {
            this.canvas1.ReleaseTouchCapture(_touchPoint.TouchDevice);
        }
    }
}

For Each _touchPoint In e.GetTouchPoints(Me.canvas1)

    If _touchPoint.Action = TouchAction.Down Then
        ' Clear the canvas and capture the touch to it.
        canvas1.Children.Clear()
        _touchPoint.TouchDevice.Capture(canvas1)

    ElseIf _touchPoint.Action = TouchAction.Move Then
        ' This is the first (primary) touch point. Just record its position.
        If _touchPoint.TouchDevice.Id = e.GetPrimaryTouchPoint(Me.canvas1).TouchDevice.Id Then
            pt1.X = _touchPoint.Position.X
            pt1.Y = _touchPoint.Position.Y

            ' This is not the first touch point; draw a line from the first point to this one.
        ElseIf _touchPoint.TouchDevice.Id <> e.GetPrimaryTouchPoint(Me.canvas1).TouchDevice.Id Then
            pt2.X = _touchPoint.Position.X
            pt2.Y = _touchPoint.Position.Y

            Dim _line As New Line()
            _line.Stroke = New RadialGradientBrush(Colors.White, Colors.Black)
            _line.X1 = pt1.X
            _line.X2 = pt2.X
            _line.Y1 = pt1.Y
            _line.Y2 = pt2.Y

            _line.StrokeThickness = 2
            Me.canvas1.Children.Add(_line)
        End If

    ElseIf _touchPoint.Action = TouchAction.Up Then
        ' If this touch is captured to the canvas, release it.
        If (_touchPoint.TouchDevice.Captured Is canvas1) Then
            canvas1.ReleaseTouchCapture(_touchPoint.TouchDevice)
        End If
    End If
Next

備註

在一組主動式觸控裝置中，第一個成為 Activated 觸控裝置的裝置是主要的觸控裝置。 例如，如果兩根手指同時觸碰螢幕，第一根手指朝下時，主要觸控裝置會代表。 如果在第二根手指仍放下時，第一根手指被抬起，主要觸控裝置就會變成 null。