```dart
import 'package:flutter/material.dart';
// Main entry point of the application
void main() {
runApp(MyApp());
}
// The root widget of the application
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Add Two Numbers', // Title of the application
theme: ThemeData(
primarySwatch: Colors.blue, // Set the primary color theme
),
home: MyHomePage(), // The main page of the app
);
}
}
// A stateful widget to handle the dynamic behavior of the main page
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
// The state for MyHomePage
class _MyHomePageState extends State<MyHomePage> {
// Controllers to handle text input for the two numbers
final TextEditingController _controller1 = TextEditingController();
final TextEditingController _controller2 = TextEditingController();
// Variable to store the result of the addition
String _result = '';
// Method to add the two numbers and update the result
void _addNumbers() {
// Parse the input texts to integers, defaulting to 0 if parsing fails
final int num1 = int.tryParse(_controller1.text) ?? 0;
final int num2 = int.tryParse(_controller2.text) ?? 0;
// Add the two numbers
final int sum = num1 + num2;
// Update the result state
setState(() {
_result = 'Result: $sum';
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Add Two Numbers'), // Title in the app bar
),
body: Padding(
padding: const EdgeInsets.all(16.0), // Padding around the content
child: Column(
children: <Widget>[
// Text field for the first number
TextField(
controller: _controller1,
keyboardType: TextInputType.number, // Set the keyboard type to number
decoration: InputDecoration(
labelText: 'Enter first number', // Label for the text field
),
),
// Text field for the second number
TextField(
controller: _controller2,
keyboardType: TextInputType.number, // Set the keyboard type to number
decoration: InputDecoration(
labelText: 'Enter second number', // Label for the text field
),
),
SizedBox(height: 20), // Add some space between the text fields and the button
// Button to trigger the addition
ElevatedButton(
onPressed: _addNumbers, // Set the onPressed callback
child: Text('Add'), // Text on the button
),
SizedBox(height: 20), // Add some space between the button and the result text
// Text widget to display the result
Text(
_result,
style: TextStyle(fontSize: 20), // Set the text size
),
],
),
),
);
}
}
```
### Explanation of Comments:
- **General Structure**: Comments explain the purpose of each major section (e.g., `main()`, `MyApp`, `MyHomePage`, etc.).
- **UI Elements**: Comments describe the purpose of each widget (e.g., `TextField`, `ElevatedButton`, `Text`, etc.).
- **Logic**: Comments within the `_addNumbers` method explain how the input is parsed and the sum is calculated.
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