Why skia looks so poorly on Android?

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i use avalonia, and I'm trying to make an Android app. There's no native Controls for rendering by skia. So i make one by myself.
This is how my program shows on Desktop:

And this is how it shows on Android real phone

I create my SkiaControl, following the example
There's a really obvious contrast of definition between the graphics on these two platforms. \
i think the problem can't result from antialias, but because of dpi? But i can't find any dpi properties on SKCanvas or SKSurface. Dpi of my phone is about 260, but the dpi how skia renders must be far less than 260.
Then i use WritableBitmap and immediatedrawingcontext of avalonia, then the definition is improved. So the problem may not be led by avalonia i think.
i have found an issue, talking about the strange problem on Android, but it didn't offer any useful suggestions
Thank you