Fibonacci 2.0

Using the Visual Studio integrated development environment and the C# programming language, we will develop a cross-platform mobile application to generate Fibonacci sequence numbers.

Information

In mathematics, the Fibonacci numbers form a sequence defined recursively as follows: it starts with 0 and 1, and each subsequent term is the sum of the previous two. The first Fibonacci numbers are: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …

• Source: Wikipedia

Start

1. Launch the Visual Studio integrated development environment.

2. Create a new project: Visual C# > Cross-Platform > Mobile App (Xamarin.Forms).

3. Name the project: Fibonacci 2.0.

MainPage.xaml

The MainPage.xaml file contains the source code for the application's user interface design and is written in XAML. Copy (Ctrl+C) and paste (Ctrl+V) the fragment below into your application

<!-- User Interface (UI): Fibonacci 2.0 -->
<StackLayout Padding="20">
        
    <!-- Title -->
    <Label Text="Fibonacci 2.0" FontSize="Large" />
        
    <!-- Limit -->
    <Label Text="Limit" />
    <Entry x:Name="boxLimit" Keyboard="Numeric" Text="1000" />
    <Button Text="Generate" Clicked="OnButtonClicked" />
        
    <!-- Numbers -->
    <ListView x:Name="boxNumbers" />
        
</StackLayout>

MainPage.xaml.cs

The MainPage.xaml.cs file contains the source code for the application's business logic and is written in C#. Copy (Ctrl+C) and paste (Ctrl+V) the fragment below into your application.

// Business Logic (BL): Fibonacci 2.0
public partial class MainPage : ContentPage
{
        // Constructor
        public MainPage()
        {
            InitializeComponent();
        }

        // Button Click Event Handler
        void OnButtonClicked(object sender, EventArgs args)
        {
            List<int> numbers = new List<int>();
            numbers.Add(1);
            numbers.Add(1);
            int limit = int.Parse(this.boxLimit.Text);
            int a = 1, b = 1, c = a + b;
            while (c < limit)
            {
                numbers.Add(c);
                a = b;
                b = c;
                c = a + b;
            }
            this.boxNumbers.ItemsSource = numbers;
        }
}

Demo

Run the application from the menu: Debug > Start Debugging or by pressing the F5 key.

Fig. 2.58 Testing the cross-platform mobile application for generating the Fibonacci sequence - Android Emulator 11 (API 30)