Example for using ternary operator in Flutter.

ternary-operator-flutter.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool isLoading = true;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            isLoading ? CircularProgressIndicator() : Text("Loading Completed"),
            SizedBox(height: 100),
            Text("Click Button to Toggle Loading"),
             SizedBox(height: 50),
            ElevatedButton(
            onPressed: () {
              setState(() {
                isLoading = !isLoading;
              });
            },
            child: Text("Toggle Loading"),
          )
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            isLoading = !isLoading;
          });
        },
      ),
    );
  }
}