You need to provide child and onPressed parameter in order to render the widget, else it won’t render, which results in non working UI.

Check out the code i modified :

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(scaffoldBackgroundColor: darkBlue),
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: SafeArea(
      child: Scaffold(
        body: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            FlatButton(
              color: Colors.red,
              onPressed:()=>printData(),
              child: Text("click"),
            ),
            FlatButton(
              color: Colors.green,
              onPressed:()=>printData(),
              child: Text("click"),
            ),
            FlatButton(
              color: Colors.blue,
              onPressed:()=>printData(),
              child: Text("click"),
            ),
          ],
        ),
      ),
    ));
  }
}

void printData(){
  print('Hello');
}

Have a look at the @required fields of the FlatButton Constructor without which it would not render.

This is a Flat button with required fields. Add your desired color to this to render it.
Without a color it renders with black text and white background.

FlatButton(
  onPressed: () {
    /*...*/
  },
  child: Text(
    "Flat Button",
  ),
)

I was having same problem. I just added “disabledColor : Colors.red”
Check screenshot.

enter image description here

In flutter App I’m trying to set color for the FlatButton But it’s not working. find the source code below.

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: SafeArea(
      child: Scaffold(
        body: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            FlatButton(
              color: Colors.red,
            ),
            FlatButton(
              color: Colors.green,
            ),
            FlatButton(
              color: Colors.blue,
            ),
          ],
        ),
      ),
    ));
  }
}

Output:

I’m flutter Beginner, Any Idea What is the issue in my code?

Thanks In Advance