将 SkiaSharp 的油漆表面与 Xamarin 形式和棱镜绑定

Question

我正在尝试使Skiasharp与Xamarin形式和棱镜一起工作。我将其与代码背后的以下页面一起工作

public partial class RoomLayoutPage : ContentPage 
{ 
SKCanvasView canvasView;
public RoomLayoutPage()
{
  InitializeComponent();
  canvasView = new SKCanvasView();
  canvasView.PaintSurface += OnCanvasViewPaintSurface;
  Content = canvasView;
}

private void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs e)
{
  SKSurface surface = e.Surface;
  SKCanvas canvas = surface.Canvas;
  canvas.Clear();
  SKPaint blackPaint = new SKPaint
  {
    Color = SKColors.Black,
  };
  canvas.DrawRect(0, 0, 100, 100, blackPaint);
}
}

，但是现在我想将其移至我的棱镜ViewModel。如果我移动它，则内容无效

1. 如何从ViewModel引用XAML元素？我宁愿不这样做，因为然后将我的ViewModel耦合到视图。

2. (优先方式(如果我在页面上放置了一个skcanvasview

我可以使用EventTocommandBehaviour

绑定到事件

    <forms:SKCanvasView>
  <forms:SKCanvasView.Behaviors>
    <behaviors:EventToCommandBehavior Command="{Binding OnCanvasViewPaintSurface}" EventName="PaintSurface"/>
  </forms:SKCanvasView.Behaviors>
</forms:SKCanvasView>

但我不确定如何绑定

的skpaintsurfaceeventargs

OnCanvasViewPaintSurface = new DelegateCommand<SKPaintSurfaceEventArgs>(OnCanvasViewPaintAction);

我假设这是此处的EventArgs选项之一https://prismlibrary.github.io/docs/xamarin-forms/eventtocommandbehavior.html？

谢谢

Answer 1

，因此使用值转换器求解它..

public class SkiaEventArgsConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
  var sKPaintSurfaceEventArgs = value as SKPaintSurfaceEventArgs;
  if (sKPaintSurfaceEventArgs == null)
  {
    throw new ArgumentException("Expected value to be of type SKPaintSurfaceEventArgs", nameof(value));
  }
  return sKPaintSurfaceEventArgs;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
  throw new NotImplementedException();
}
}

不完全确定为什么它不能自动转换，但起作用