JSON Reader 2.0

Using the Visual Studio integrated development environment and the C# programming language, we will develop a cross-platform mobile application for downloading Chuck Norris jokes in JSON format.

Information

JSON (JavaScript Object Notation) is a text-based open standard designed for human-readable data interchange. It originates from the JavaScript scripting language to represent simple data structures and associative arrays called objects.

• 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: JSON Reader 2.0.

Add additional packages to the project by installing Newtonsoft.Json from: Tools > NuGet Package Manager > Package Manager Console, by running the following command in the console:

PM> Install-Package Newtonsoft.Json -Version 13.0.1

Root.cs

Add a new class Root.cs that will be used to deserialize the data returned by the service.

public class Root
{
    public List<object> categories { get; set; }

    public string created_at { get; set; }

    public string icon_url { get; set; }

    public string id { get; set; }

    public string updated_at { get; set; }

    public string url { get; set; }

    public string value { get; set; }
}

Note

1. Load and copy an example JSON from: https://api.chucknorris.io/jokes/random

2. Generate the C# class for the selected JSON from: http://json2csharp.com/

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): JSON Reader 2.0 -->
<StackLayout Padding="50">

        <!-- Title -->
        <Label Text="JSON Reader 2.0" FontSize="Large" FontAttributes="Bold" />

        <!-- Buttons -->
        <StackLayout Orientation="Horizontal">
            <Button Text="New Joke" Clicked="NewJokeButtonClickedEventHandler" />
            <Button Text="Tell Joke" Clicked="TellJokeButtonClickedEventHandler" />
        </StackLayout>
        
        <!-- Joke -->
        <Label x:Name="JOKE" FontSize="Large" />

</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): JSON Reader 2.0
public partial class MainPage : ContentPage
{
        /// <summary>
        /// Constructor
        /// </summary>
        public MainPage()
        {
            InitializeComponent(); 
        }

        /// <summary>
        /// New Joke Button Clicked Event Handler
        /// </summary>
        private async void NewJokeButtonClickedEventHandler(object sender, EventArgs e)
        {
            // 1. Http Client
            HttpClient client = new HttpClient();

            // 2. Http Request to Receive JSON Response
            string json = await client.GetStringAsync(new Uri("https://api.chucknorris.io/jokes/random"));

            // 3. Deserialize JSON to Object
            Joke joke = JsonConvert.DeserializeObject<Joke>(json);

            // 4. Show the Joke in the UI
            JOKE.Text = joke.value;
        }

        /// <summary>
        /// Tell Joke Button Clicked Event Handler
        /// </summary>
        private async void TellJokeButtonClickedEventHandler(object sender, EventArgs e)
        {
            var joke = JOKE.Text;
            if (joke != "")
            {
                await TextToSpeech.SpeakAsync(joke);
            }
        }
}

Demo

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

Fig. 2.63. Demonstration of the cross-platform mobile application for downloading Chuck Norris jokes