MVVM (Prism), SKCanvasView and Canvas in Xamarin Forms.

[Surfrat]

Hi,

I am trying to get the canvas in the PaintSurfaceCommand. How do I do this?

I have tried the following:

XAML:

skiaSharp:SKCanvasView
                        x:Name="CanvasView"
                        EnableTouchEvents="True" >

                        <skiaSharp:SKCanvasView.Behaviors>
                            <prism:EventToCommandBehavior EventName="PaintSurface"
                                                          Command="{Binding PaintSurfaceCommand}"
                                                          CommandParameter="{x:Reference CanvasView}"/>
                        </skiaSharp:SKCanvasView.Behaviors>

                    </skiaSharp:SKCanvasView>

View|Model.cs:

#region Command PaintSurfaceCommand

        private DelegateCommand<object> _paintSurfaceCommand;

        public DelegateCommand<object> PaintSurfaceCommand => _paintSurfaceCommand ??= new      DelegateCommand<object>(ExecutePaintSurfaceCommand);

        private void ExecutePaintSurfaceCommand(object obj)
        {
            //if (Bitmap != null)
            //{
            //    float scale = Math.Min((float)info.Width / libraryBitmap.Width,
            //        info.Height / 3f / libraryBitmap.Height);

            //    float left = (info.Width - scale * libraryBitmap.Width) / 2;
            //    float top = (info.Height / 3 - scale * libraryBitmap.Height) / 2;
            //    float right = left + scale * libraryBitmap.Width;
            //    float bottom = top + scale * libraryBitmap.Height;
            //    SKRect rect = new SKRect(left, top, right, bottom);
            //    rect.Offset(0, 2 * info.Height / 3);

            //    canvas.DrawBitmap(libraryBitmap, rect);
            //}
        }

        #endregion

Thanks

Mark.

[Surfrat]

Here is the solution:

XAML:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:prism="http://prismlibrary.com"
             prism:ViewModelLocator.AutowireViewModel="True"  
             xmlns:button="clr-namespace:Syncfusion.XForms.Buttons;assembly=Syncfusion.Buttons.XForms"
             xmlns:skiaSharp="clr-namespace:SkiaSharp.Views.Forms;assembly=SkiaSharp.Views.Forms"
             xmlns:converters="clr-namespace:DressMe.Converters;assembly=DressMe"
             Title="Create"
             BackgroundColor="{StaticResource PageBackgroundColor}"
             x:Class="DressMe.Views.Create"
             x:Name="CreateXaml">

    <ContentPage.Resources>
        <ResourceDictionary>
            <converters:PaintSurfaceEventArgsConverter x:Key="PaintSurfaceEventArgsConverter" />
        </ResourceDictionary>
    </ContentPage.Resources>

<skiaSharp:SKCanvasView
                        EnableTouchEvents="True" >

                        <skiaSharp:SKCanvasView.Behaviors>
                            <prism:EventToCommandBehavior EventName="PaintSurface"
                                                          Command="{Binding PaintSurfaceCommand}"
                                                          EventArgsConverter="{StaticResource PaintSurfaceEventArgsConverter}"
                                                          EventArgsConverterParameter="TestParam"/>
                        </skiaSharp:SKCanvasView.Behaviors>

                    </skiaSharp:SKCanvasView>

PaintSurfaceEventArgsConverter.cs:

namespace DressMe.Converters
{
    public class PaintSurfaceEventArgsConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            SKPaintSurfaceEventArgs eventArgs = value as SKPaintSurfaceEventArgs;
            Dictionary<string, object> eventArgsResult = new Dictionary<string, object>();

            if (eventArgs != null)
            {
                eventArgsResult.Add("EventArgs", eventArgs);
                eventArgsResult.Add("Parameter", parameter);
            }

            return eventArgsResult;
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }

}

ViewModel:

#region Command PaintSurfaceCommand

        private DelegateCommand<Dictionary<string, object>> _paintSurfaceCommand;

        public DelegateCommand<Dictionary<string, object>> PaintSurfaceCommand => _paintSurfaceCommand ??=
            new DelegateCommand<Dictionary<string, object>>(ExecutePaintSurfaceCommand);

        private void ExecutePaintSurfaceCommand(Dictionary<string, object> eventArgsResult)
        {

            SKPaintSurfaceEventArgs eventArgs = (SKPaintSurfaceEventArgs)eventArgsResult["EventArgs"];
            string parameter = (string)eventArgsResult["Parameter"];

            if (eventArgs != null)
            {
                SKImageInfo imageInfo = eventArgs.Info;
                SKSurface surface = eventArgs.Surface;
                SKCanvas canvas = surface.Canvas;

                int width = imageInfo.Width;
                int height = imageInfo.Height;
            }

        }

        #endregion

Thanks

Mark.