Flutter Circular Progress Bar

To create a circular progress bar in Flutter, you can use the CircularProgressIndicator widget. Below is a simple example of how to implement it:
Basic Circular Progress Bar

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Circular Progress Bar Example'),
        ),
        body: Center(
          child: CircularProgressIndicator(),
        ),
      ),
    );
  }
}

Customized Circular Progress Bar
You can customize the progress bar with different colors, thickness, and more:

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Circular Progress Bar Example'),
        ),
        body: Center(
          child: CircularProgressIndicator(
            valueColor: AlwaysStoppedAnimation<Color>(Colors.blue),
            backgroundColor: Colors.grey[300],
            strokeWidth: 8.0,
          ),
        ),
      ),
    );
  }
}

Circular Progress Bar with Percentage
If you want to show a circular progress bar that displays progress (e.g., a percentage):

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  double progressValue = 0.0;

  void updateProgress() {
    setState(() {
      progressValue += 0.1;
      if (progressValue > 1.0) {
        progressValue = 0.0;
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Circular Progress Bar with Percentage'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              CircularProgressIndicator(
                value: progressValue,
                valueColor: AlwaysStoppedAnimation<Color>(Colors.blue),
                backgroundColor: Colors.grey[300],
                strokeWidth: 8.0,
              ),
              SizedBox(height: 20),
              ElevatedButton(
                onPressed: updateProgress,
                child: Text('Increase Progress'),
              ),
              SizedBox(height: 20),
              Text('${(progressValue * 100).round()}%'),
            ],
          ),
        ),
      ),
    );
  }
}

Explanation:

• CircularProgressIndicator(): A widget that displays a circular progress indicator.
• valueColor: Specifies the color of the progress indicator.
• backgroundColor: Specifies the color of the track behind the progress indicator.
• strokeWidth: Sets the thickness of the progress indicator's stroke.
• value: If null, the progress indicator shows an indeterminate spinner. If a value is provided, it represents the completion percentage of the task, where 1.0 means 100%.