Flutter - Outputting Widgets Conditionally

import 'package:flutter/material.dart';

/// Entry point of the Flutter application
void main() => runApp(MyApp());

/// Root widget of the application
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'GeeksforGeeks',

      /// Hides the debug banner in the top-right corner
      debugShowCheckedModeBanner: false,

      /// Sets the primary color theme for the app
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),

      /// Sets the default home page of the app
      home: HomePage(),
    );
  }
}

/// HomePage widget that represents the main UI screen
class HomePage extends StatelessWidget {

  /// A boolean flag to conditionally display widgets
  final bool checked = true;

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(

        /// App bar with title
        appBar: AppBar(
          title: Text('GeeksforGeeks'),
        ),

        /// Body of the screen with vertical layout
        body: Column(
          children: <Widget>[
            
            /// Always visible text widget
            Text(
              'First Widget',
              style: TextStyle(
                fontSize: 18,
                fontWeight: FontWeight.bold,
              ),
            ),

            /// Conditionally renders this Text widget if [checked] is true
            if (checked)
              Text(
                'Second Widget',
                style: TextStyle(
                  fontSize: 18,
                  fontWeight: FontWeight.bold,
                ),
              ),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';

/// Entry point of the application
void main() => runApp(MyApp());

/// Root widget of the application
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'GeeksforGeeks',

      /// Hides the debug banner in the top-right corner of the screen
      debugShowCheckedModeBanner: false,

      /// Sets the primary theme color of the application
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),

      /// Sets the HomePage as the default screen
      home: HomePage(),
    );
  }
}

/// A stateless widget representing the home screen
class HomePage extends StatelessWidget {

  /// Boolean variable used to conditionally show a widget
  final bool checked = true;

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(

        /// App bar with title
        appBar: AppBar(
          title: Text('GeeksforGeeks'),
        ),

        /// Body content arranged vertically
        body: Column(
          children: <Widget>[
            
            /// Always visible text widget
            Text(
              'First Widget',
              style: TextStyle(
                fontSize: 18,
                fontWeight: FontWeight.bold,
              ),
            ),

            /// Conditionally renders 'Second Widget' if [checked] is true,
            /// otherwise renders an empty container (invisible placeholder)
            checked? Text(
                    'Second Widget',
                    style: TextStyle(
                      fontSize: 18,
                      fontWeight: FontWeight.bold,
                    ),
                  )
                : Container(),
          ],
        ),
      ),
    );
  }
}

import 'package:flutter/material.dart';

/// Entry point of the Flutter application
void main() => runApp(MyApp());

/// Root widget of the app
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'GeeksforGeeks',

      // Hide the debug banner on the top right
      debugShowCheckedModeBanner: false,

      // Set the app's theme
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),

      // Set the home page of the app
      home: HomePage(),
    );
  }
}

/// A stateless widget representing the home screen
class HomePage extends StatelessWidget {
  
  // A boolean variable used to control conditional rendering
  final checked = true;

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(

        /// AppBar with a title
        appBar: AppBar(
          title: Text('GeeksforGeeks'),
        ),

        /// Main content of the page
        body: Column(
          children: <Widget>[
            
            // A Text widget always shown
            Text(
              'First Widget',
              style: TextStyle(
                fontSize: 18,
                fontWeight: FontWeight.bold,
              ),
            ),

            // A custom function that returns a widget
            condition(),
          ],
        ),
      ),
    );
  }

  /// A method that returns a widget based on a condition.
  /// Uses a switch statement to decide which widget to show
  Widget condition() {
    // Declare a variable to hold the widget
    Widget widget;

    // Use a switch-case for conditional logic
    // Though a simple if-else is more suitable for booleans,
    // this demonstrates switch usage for clarity
    switch (checked) {
      case true:
        widget = Text(
          'Second Widget',
          style: TextStyle(
            fontSize: 18,
            fontWeight: FontWeight.bold,
          ),
        );
        break;
      case false:
        widget = Container(); // Return empty widget if condition is false
        break;
      default:
        widget = Container(); // Default case for safety
    }

    // Return the appropriate widget
    return widget;
  }
}

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

/// Root widget of the application
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'GeeksforGeeks',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.green,
      ),
      home: HomePage(),
    );
  }
}

/// StatefulWidget to toggle and show content conditionally
class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  bool _selected = false;

  /// Build method for the UI
  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          title: Text('GeeksforGeeks'),
        ),
        body: Padding(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            children: [
              /// Checkbox tile with toggle logic
              CheckboxListTile(
                title: Text(
                  'Data Structures',
                  style: TextStyle(fontSize: 18, fontWeight: FontWeight.w500),
                ),
                value: _selected,
                onChanged: (value) {
                  setState(() {
                    _selected = value ?? false;
                  });
                },
              ),

              SizedBox(height: 20),

              /// Show content if checkbox is selected
              if (_selected) ...[
                Expanded(
                  child: ListView(
                    children: [
                      _buildTopicItem('Arrays'),
                      _buildTopicItem('LinkedList'),
                      _buildTopicItem('Stack'),
                      _buildTopicItem('Tree'),
                    ],
                  ),
                ),
              ]
            ],
          ),
        ),
      ),
    );
  }

  /// A reusable widget to render each topic
  Widget _buildTopicItem(String title) {
    return Card(
      elevation: 2,
      margin: const EdgeInsets.symmetric(vertical: 6),
      child: ListTile(
        leading: Icon(Icons.bookmark),
        title: Text(
          title,
          style: TextStyle(fontSize: 16),
        ),
      ),
    );
  }
}