Yellow lines under Text Widgets in Flutter?

Add Material widget as root element.

@override
  Widget build(BuildContext context) {
    return Material(
        type: MaterialType.transparency,
        child: new Container(

All you need to do is provide a Material widget, or a Scaffold which internally covers this widget. You can do that in the following ways:

• Use Material (simple and better):

  Material(
    color: Colors.transparent, // <-- Add this, if needed
    child: Text('Hello'),
  )
  

• Set Text.style property:

  Text(
    'Hello',
    style: TextStyle(decoration: TextDecoration.none), // Set this
  )
  

• Provide Scaffold:

  Scaffold(body: Text('Hello'))
  

Fixing yellow text issues when using Hero :

As aaronvargas mentioned, you can wrap your child in Material when using Hero on both sides. For example:

Hero(
  tag: 'fooTag',
  child: Material( // <--- Provide Material
    type: MaterialType.transparency,
    child: YourWidget(),
  ),
);

Text style has a decoration argument that can be set to none

Text("My Text",
  style: TextStyle(
    decoration: TextDecoration.none,
  )
);

Also, as others have mentioned, if your Text widget is in the tree of a Scaffold or Material widget you won't need the decoration text style.

Just adding another way I encounter to these answers.

Wrap the root Widget around a DefaultTextStyle widget. Altering each Text widget is not a necessity here.

DefaultTextStyle(
    style: TextStyle(decoration: TextDecoration.none), 
    child : Your_RootWidget
)

Hope it helps someone.

Also you can use decoration: TextDecoration.none to remove underline

You should add Material and Scaffold widgets in main.dart file

 MaterialApp(
  home: Scaffold(
    body: Text('Hello world'),
  ),
);

Before

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: [
        Center(
          child: Text(
            "21:34",
            style: TextStyle(fontSize: 50),
          ),
        ),
        Center(
          child: Text(
            "Wakey - wakey",
            style: TextStyle(fontSize: 20),
          ),
        )
      ],
    );
  }

After (Solution):

Here Wrap the current top or parent widget with Scaffold widget

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Center(
            child: Text(
              "21:34",
              style: TextStyle(fontSize: 50),
            ),
          ),
          Center(
            child: Text(
              "Wakey - wakey",
              style: TextStyle(fontSize: 20),
            ),
          )
        ],
      ),
    );
  }

Full code:Dartpad or Live code

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: sta()));

class sta extends StatefulWidget {
  const sta({Key? key}) : super(key: key);

  @override
  State<sta> createState() => _staState();
}

var isShow = false;


class _staState extends State<sta> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Center(
            child: Text(
              "21:34",
              style: TextStyle(fontSize: 50),
            ),
          ),
          Center(
            child: Text(
              "Wakey - wakey",
              style: TextStyle(fontSize: 20),
            ),
          )
        ],
      ),
    );
  }
}

You just need to add Material root widget.

      @override
       Widget build(BuildContext context) {
      return Material(
         child: new Container(),
        );
       }

There is an other solution for this , especially if you are using multiple pages wrapped under main.dart file You can do something like this:

  child: MaterialApp(
    home: Material(child: Wrapper()),
  ),

This will remove the yellow lines under text that is present in any pages referenced/used under wrapper.

problem: your widget doesn't have default text style,

solution: wrap it in one!

DefaultTextStyle(
    style: TextStyle(),
    child: yourWidget,
  );

remember if you dont set any color, default text color is white!

The yellow lines come from _errorTextStyle. The documentation states that you should define a DefaultTextStyle parent (or use Material, which does this for you):

MaterialApp uses this TextStyle as its DefaultTextStyle to encourage developers to be intentional about their DefaultTextStyle.

In Material Design, most Text widgets are contained in Material widgets, which sets a specific DefaultTextStyle. If you're seeing text that uses this text style, consider putting your text in a Material widget (or another widget that sets a DefaultTextStyle).

Developing Flutter apps without material is not something most people do, but if that's your use case, you should use DefaultTextStyle.

Contrary to the accepted answer, Theme does not set a DefaultTextStyle, so it does not solve your problem. Scaffold does solve the problem, as it contains Material, which in turn defines DefaultTextStyle, but Scaffold is a bit more than you need for a Dialog, Hero, etc.

To permanently solve this for your whole app, you could set the DefaultTextStyle in your MaterialApp builder. This solves the issue for all the components of your app, not just the current screen you're working on.

You can also have your scaffold as the home for your MaterialApp. This worked for me.

return MaterialApp(
  home: Scaffold(
    body: Container(
      child: SingleChildScrollView(child: Text('Test')),
    ),
  ),
);

I recommend this approach because you could do it once and it will override your whole app.

Add DefaultTextStyle under builder of our MaterialApp like so:

child: MaterialApp(      
  ...
  ...
  theme: yourThemeData,
  builder: (context, child) => DefaultTextStyle(
    style: yourThemeData.textTheme.bodyText1,
    child: child,
  ),
),

By doing so we don't need to specify a style or having DefaultTextTheme every time we want to use showDialog or Overlay.

Use a DefaultTextStyle() widget to set the textstyle of your text.

DefaultTextStyle(
  style: kTempTextStyle,
  child: Text('Hello world'),
)

you can give your own textstyle as you want.

const kTempTextStyle = TextStyle(
  fontFamily: 'Spartan MB',
  fontSize: 100.0,
  decoration: null,
);

If you get this problem in you main page, do not forget to wrap with scaffold. But if you are getting those underlines in your alert dialog or in a pop up page (where you can't wrap with scaffold), just add decoration to your text widget.

   decoration: TextDecoration.none, 

The text has a hidden default text style .The problem arises because you can't provide this to any parent widget like Scaffold. Text widget takes the default style. for your solution either you can change the DefaultTextStyle like this.

DefaultTextStyle(
    style: TextStyle(),
    child: yourTextWidget,
  );

or just wrap into Scaffold, Scaffold is a widget. that provides scaffolding for pages in your app. like this

 MaterialApp(
  home: Scaffold(
    body: Text('Wakey Wakey!'),
  ),
);

for more info just walk through this Flutter Official video.

Yellow underline text | Decoding Flutter

wrap your build widget with Material widget

@override Widget build(BuildContext context) { return Material ( ... );

it will fix the text yellow underline issue

It could also happen if you add MaterialApp more than once. Example is when you have MaterialApp in the Main widget and also in a sub widget. The sub widget will have to problem talked about but the main widget will display text as normal.

Try wrapping your widget with Material widget like a below:

Material(color: Colors.white, child: YourWidget())