how to change background for inputs in UnderlineDecoration?

[OlegBrony]

is there a prop about changing background color for UnderlineDecoration? I want to make something like this

I tried to make it with BoxLooseDecoration and solid color, but I can't change border to make it only on bottom.

[TinoGuo]

you can use solidColor since 3.0.4, because this lib initial purpose only for pin and i ignored the underlineDecoration. anyway, you can use it now.