TouchFrameEventArgs.GetPrimaryTouchPoint(IInputElement) Metode

Definisi

Ruang nama:

System.Windows.Input

Rakitan:

PresentationCore.dll

Mengembalikan titik sentuh saat ini dari perangkat sentuh utama relatif terhadap elemen yang ditentukan.

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

Parameter

relativeTo

IInputElement

Elemen yang menentukan ruang koordinat. Untuk menggunakan koordinat absolut WPF, tentukan relativeTo sebagai null.

Mengembalikan

TouchPoint

Posisi primer TouchDevice saat ini relatif terhadap elemen yang ditentukan; atau null jika primer TouchDevice tidak aktif.

Contoh

Kode berikut memproses titik sentuh yang diambil dari TouchFrameEventArgs. Ketika sentuhan ditekan pada Canvas, TouchDevice diambil ke Canvas. Ketika sentuhan diangkat, dilepaskan TouchDevice . Ketika sentuhan bergerak melintasi Canvas, Id dicentang. Id Jika cocok dengan Id titik sentuh utama, yang menunjukkan sentuhan pertama, lokasinya akan direkam. Jika gerakan berasal dari sentuhan kedua, garis digambar dari posisi sentuhan pertama ke posisi sentuhan kedua.

Contoh ini adalah bagian dari contoh yang lebih besar yang tersedia dalam Touch gambaran umum kelas.

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

Keterangan

Dalam satu set perangkat sentuh aktif, perangkat pertama yang akan menjadi Activated perangkat sentuh utama. Misalnya, jika dua jari menyentuh layar, jari pertama yang turun diwakili oleh perangkat sentuh utama. Jika jari pertama diangkat saat jari kedua masih turun, perangkat sentuh utama menjadi null.