2022-2-17 触摸屏幕移动

#region 鼠标
        private void canvas_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            targetElement = Mouse.DirectlyOver as UIElement;
            if (targetElement != null)
            {
                targetPoint = e.GetPosition(NGEntry);
            }
        }

        private void canvas_PreviewMouseMove(object sender, MouseEventArgs e)
        {
            if (e.LeftButton == MouseButtonState.Pressed && targetElement != null)
            {
                var pCanvas = e.GetPosition(borderName);

                //double gridtop = Convert.ToDouble(NGEntry.GetValue(Canvas.TopProperty));

                //NGEntry.SetValue(Canvas.TopProperty, pCanvas.Y - targetPoint.Y);
                //Translate.Y = pCanvas.Y - targetPoint.Y;
                var y = pCanvas.Y - targetPoint.Y;
                Viewer.ScrollToVerticalOffset(Viewer.VerticalOffset - y);
            }
        }

        private void canvas_PreviewMouseUp(object sender, MouseButtonEventArgs e)
        {
            double gridtop = -Viewer.VerticalOffset;
            double gridh = NGEntry.ActualHeight;
            double viewh = Viewer.ActualHeight;
            if (gridtop > 0)
            {
                //NGEntry.SetValue(Canvas.TopProperty, 0d);
                //Translate.Y = 0d;
                Viewer.ScrollToVerticalOffset(0d);
            }
            if (viewh + (Math.Abs(gridtop)) > gridh)
            {
                //NGEntry.SetValue(Canvas.TopProperty, viewh - gridh);
                //Translate.Y = viewh - gridh;
                Viewer.ScrollToVerticalOffset(viewh - gridh);
            }
        }
        #endregion

        #region 触摸
        private void canvas_TouchDown(object sender, TouchEventArgs e)
        {
            targetElement = Mouse.DirectlyOver as UIElement;
            if (targetElement != null)
            {
                targetPoint = e.GetTouchPoint(NGEntry).Position;
            }
        }

        private void canvas_TouchUp(object sender, TouchEventArgs e)
        {
            double gridtop = -Viewer.VerticalOffset;
            double gridh = NGEntry.ActualHeight;
            double viewh = Viewer.ActualHeight;
            if (gridtop > 0)
            {
                //NGEntry.SetValue(Canvas.TopProperty, 0d);
                //Translate.Y = 0d;
                Viewer.ScrollToVerticalOffset(0d);
            }
            if (viewh + (Math.Abs(gridtop)) > gridh)
            {
                //NGEntry.SetValue(Canvas.TopProperty, viewh - gridh);
                //Translate.Y = viewh - gridh;
                Viewer.ScrollToVerticalOffset(viewh - gridh);
            }
        }

        private void canvas_TouchMove(object sender, TouchEventArgs e)
        {
            if (targetElement != null)
            {
                var pCanvas = e.GetTouchPoint(borderName).Position;

                //double gridtop = Convert.ToDouble(NGEntry.GetValue(Canvas.TopProperty));

                //NGEntry.SetValue(Canvas.TopProperty, pCanvas.Y - targetPoint.Y);
                //Translate.Y = pCanvas.Y - targetPoint.Y;
                var y = pCanvas.Y - targetPoint.Y;
                Viewer.ScrollToVerticalOffset(Viewer.VerticalOffset - y);
            }
        }
        #endregion