使用 Xamarin Forms 和 Prism 绑定 SkiaSharp 的 PaintSurface

Question

我正在尝试让 SkiaSharp 与 Xamarin Forms 和 Prism 一起工作。我让它在代码

后面的页面上工作

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);
}
}

但现在我想将其移至我的 Prism ViewModel。如果我移动它，则内容无效

如何从 ViewModel 引用 xaml 元素？我不想这样做，因为我的 ViewModel 然后与视图耦合。
（首选方式）如果我在我的页面上放置一个 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>

但我不确定如何为

绑定 SKPaintSurfaceEventArgs

OnCanvasViewPaintSurface = new DelegateCommand<SKPaintSurfaceEventArgs>(OnCanvasViewPaintAction);

我假设它是此处的 EventArgs 选项之一 https://prismlibrary.github.io/docs/xamarin-forms/EventToCommandBehavior.html ?

谢谢

Answer 1

所以使用值转换器解决了它..

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它但它有效

使用 Xamarin Forms 和 Prism 绑定 SkiaSharp 的 PaintSurface

Binding SkiaSharp's PaintSurface with Xamarin Forms and Prism

prism

xamarin

skiasharp