Xamarin Xam.Plugins.Forms.Svg更改SvgPath以重新呈现图像

Question

I use Xam.Plugins.Forms.Svg to support svg images. I need to change the image, so I tried:

binding in xaml :

<abstractions:SvgImage
    SvgPath="{Binding CurrentWeather.IconSource, StringFormat='Umbrella.Images.{0:F0}.svg'}"
    ....
    />

to change it directly from C#:

icon.SvgPath = "Umbrella.Images." + currentWeather.IconSource + ".svg";

The SvgPath attribute does change, but the image doesn't rerender.

Is there any solution to this?

Answer 1

It is an issue in the way the renderers are written, you would need to create a new SvgImage object and replace the current on in your page the way the renderers work in order for the static Image to be updated from a new SVG file.

You can patch the renderers by overriding the OnElementPropertyChanged event and respond to SvgPath PropertyName changes:

iOS Example:

protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
    base.OnElementPropertyChanged(sender, e);
    if (e.PropertyName == "SvgPath")
    {
        var svgStream = _formsControl.SvgAssembly.GetManifestResourceStream(_formsControl.SvgPath);
        var reader = new SvgReader(new StreamReader(svgStream), new StylesParser(new ValuesParser()), new ValuesParser());
        var graphics = reader.Graphic;
        var canvas = new ApplePlatform().CreateImageCanvas(graphics.Size);
        graphics.Draw(canvas);
        var image = canvas.GetImage();
        var uiImage = image.GetUIImage();
        Control.Image = uiImage;
    }
}

Ref: https://github.com/paulpatarinski/Xamarin.Forms.Plugins/blob/eab230fcf4158a288387727c15903a954e01cdaa/SVG/SVG/SVG.Forms.Plugin.Android/SvgImageRenderer.cs

Ref: https://github.com/paulpatarinski/Xamarin.Forms.Plugins/blob/eab230fcf4158a288387727c15903a954e01cdaa/SVG/SVG/SVG.Forms.Plugin.iOS/SvgImageRenderer.cs