我需要如果用户用一根手指触摸画布控件，绘图过程必须开始，如果用户用两根手指触摸画布控件，画布区域必须滚动/平移。我怎么能这样做？
由于
答案 0 :(得分：1)
我们可以使用指针事件来检测UWP中的多个手指输入。例如：
func scrollViewDidScroll(scrollView: UIScrollView) {
if tb_time1 == scrollView {
tb_time2.contentOffset = tb_time1.contentOffset
}else if tb_time2 == scrollView {
tb_time1.contentOffset = tb_time2.contentOffset
}
}
如您所见，我将<ScrollViewer x:Name="scrollViewer" VerticalScrollBarVisibility="Hidden" HorizontalScrollBarVisibility="Hidden"
VerticalScrollMode="Disabled" HorizontalScrollMode="Disabled">
<canvas:CanvasControl x:Name="canvasControl" Draw="CanvasControl_Draw" CreateResources="canvasControl_CreateResources" ClearColor="CornflowerBlue"
PointerPressed="canvasControl_PointerPressed" PointerReleased="canvasControl_PointerReleased" PointerExited="canvasControl_PointerReleased"
PointerCanceled="canvasControl_PointerPressed"
PointerMoved="canvasControl_PointerMoved" Width="1200">
</canvas:CanvasControl>
</ScrollViewer>
放出ScrollViewer，因此画布也可以滚动。代码背后：
canvas:CanvasControl当用一根手指绘制时，在我的演示中，画布将仅在指针释放时更新其布局。您可以更改代码，以便在每次移动指针时更新画布。但我认为，为此，您需要将private CanvasRenderTarget renderTarget;
private async void CanvasControl_Draw(Microsoft.Graphics.Canvas.UI.Xaml.CanvasControl sender, Microsoft.Graphics.Canvas.UI.Xaml.CanvasDrawEventArgs args)
{
args.DrawingSession.DrawImage(renderTarget);
}
private void canvasControl_CreateResources(CanvasControl sender, Microsoft.Graphics.Canvas.UI.CanvasCreateResourcesEventArgs args)
{
renderTarget = new CanvasRenderTarget(sender, (float)sender.ActualWidth, (float)sender.ActualHeight);
}
private List<PointerPoint> m_pt = new List<PointerPoint>();
private void canvasControl_PointerPressed(object sender, PointerRoutedEventArgs e)
{
PointerPoint cp = e.GetCurrentPoint(canvasControl);
m_pt.Add(cp);
if (m_pt.Count == 2)
{
scrollViewer.HorizontalScrollMode = ScrollMode.Enabled;
scrollViewer.VerticalScrollMode = ScrollMode.Enabled;
}
}
private void canvasControl_PointerReleased(object sender, PointerRoutedEventArgs e)
{
if (m_pt.Count == 1)
canvasControl.Invalidate();
scrollViewer.HorizontalScrollMode = ScrollMode.Disabled;
scrollViewer.VerticalScrollMode = ScrollMode.Disabled;
m_pt.Clear();
}
private void canvasControl_PointerMoved(object sender, PointerRoutedEventArgs e)
{
if (m_pt.Count == 1)
{
var pt = e.GetCurrentPoint(canvasControl);
using (var ds = renderTarget.CreateDrawingSession())
{
ds.DrawCircle(new Vector2((float)pt.Position.X, (float)pt.Position.Y), 2, Colors.Black);
}
}
else
{
if (m_pt.Count > 2)
m_pt.Clear();
}
}
替换为另一个Win2D控件，有关详细信息，请参阅CanvasControl.Invalidate Method。