GoogleFont-Weight issue on copyWith - flutter

Question

I'm creating a text-style model and using getter to have the text-Style that use google_fonts. The issue occurs when I provide fontWeight: property. Also, the fontWeight is not providing similar look as GoogleFont.
I've tested on another project, rebuilding the project, using html renderer. I've checked this question but it is not working.
Comparison between styles
But Looks from GoogleFont
flutter doctor -v no issue
Flutter (Channel stable, 2.5.2, on Microsoft Windows [Version
10.0.19043.1288], locale en-US)
• Flutter version 2.5.2 at C:\Tools\flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision 3595343e20 (3 weeks ago), 2021-09-30 12:58:18
-0700
• Engine revision 6ac856380f
• Dart version 2.14.3
Model class
class AppTextStyles {
static TextStyle get normalMidBlod => const TextStyle(
fontWeight: FontWeight.bold,
fontSize: 33,
);
static TextStyle get latoMidBlod => GoogleFonts.lato(
fontWeight: FontWeight.bold, //this one
color: Colors.black,
fontSize: 33,
);
static TextStyle get lato => GoogleFonts.lato(
color: Colors.black,
fontSize: 33,
);
}
Test Widget
class Test extends StatelessWidget {
const Test({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Row(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.center,
children: [
Column(
children: const [
Text("style: TextStyle.."),
Text(
"w100",
style: TextStyle(fontWeight: FontWeight.w100, fontSize: 33),
),
Text(
"w200",
style: TextStyle(fontWeight: FontWeight.w200, fontSize: 33),
),
Text(
"w300",
style: TextStyle(fontWeight: FontWeight.w300, fontSize: 33),
),
Text(
"w400",
style: TextStyle(fontWeight: FontWeight.w400, fontSize: 33),
),
Text(
" w500",
style: TextStyle(fontWeight: FontWeight.w500, fontSize: 33),
),
Text(
" w600",
style: TextStyle(fontWeight: FontWeight.w600, fontSize: 33),
),
Text(
" w700",
style: TextStyle(fontWeight: FontWeight.w700, fontSize: 33),
),
Text(
" w800",
style: TextStyle(fontWeight: FontWeight.w800, fontSize: 33),
),
Text(
" w900",
style: TextStyle(fontWeight: FontWeight.w900, fontSize: 33),
),
],
),
const SizedBox(
width: 30,
),
Column(
children: [
Text("normalMidBlod.copyWith"),
Text(
"w100",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w100),
),
Text(
"w200",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w200),
),
Text(
"w300",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w300),
),
Text(
"w400",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w400),
),
Text(
" w500",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w500),
),
Text(
" w600",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w600),
),
Text(
" w700",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w700),
),
Text(
" w800",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w800),
),
Text(
" w900",
style: AppTextStyles.normalMidBlod
.copyWith(fontWeight: FontWeight.w900),
),
],
),
const SizedBox(
width: 30,
),
RichText(
text: TextSpan(
children: [
TextSpan(text: "latoBold.copyWith \n"),
TextSpan(
text: "w100 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w100),
),
TextSpan(
text: "w200 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w200),
),
TextSpan(
text: "w300 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w300),
),
TextSpan(
text: "w400 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w400),
),
TextSpan(
text: " w500 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w500),
),
TextSpan(
text: " w600 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w600),
),
TextSpan(
text: " w700 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w700),
),
TextSpan(
text: " w800 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w800),
),
TextSpan(
text: " w900 \n",
style: AppTextStyles.latoMidBlod
.copyWith(fontWeight: FontWeight.w900),
),
],
),
),
const SizedBox(
width: 30,
),
RichText(
text: TextSpan(
children: [
TextSpan(text: "lato.copyWith \n"),
TextSpan(
text: "w100 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w100),
),
TextSpan(
text: "w200 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w200),
),
TextSpan(
text: "w300 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w300),
),
TextSpan(
text: "w400 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w400),
),
TextSpan(
text: " w500 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w500),
),
TextSpan(
text: " w600 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w600),
),
TextSpan(
text: " w700 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w700),
),
TextSpan(
text: " w800 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w800),
),
TextSpan(
text: " w900 \n",
style:
AppTextStyles.lato.copyWith(fontWeight: FontWeight.w900),
),
],
),
)
],
),
);
}
}

Answer 1

Only certain fonts support one ttf file with different weights. If you notice the alphabet g it looks different in each weight. You may have to download the full font family from Google fonts and include that in your pubspec.yaml under assets. It should work.
Check https://pub.dev/packages/google_fonts bundling font in application assets section.

Answer 2

There is a bug on the google_fonts_flutter package repo that talks about this: https://github.com/material-foundation/google-fonts-flutter/issues/141
To summarize, when you create a Google Font TextStyle, the fontFamily is set to the original weight you specified (ex. 'poppins-w400') instead of the general fontFamily name ('poppins').
You can fix this by specifying the fontFamily in your copyWith method.
TextSpan(
text: " w900 \n",
style: AppTextStyles.latoMidBlod
.copyWith(
fontWeight: FontWeight.w900,
fontFamily: GoogleFonts.poppins().fontFamily,
),
),