The topic shows how to create and display a “Hello World” text using a text label. It also demonstrates how you can react to touch events on the application screen.

To build and run the application, you must use Visual Studio on Windows® or Visual Studio Code on Linux.

Figure: Hello World

To create an application that displays the “Hello World” text label:

1. Declare the required system and NUI namespaces:

   using System;
   using System.Runtime.InteropServices;
   using Tizen.NUI;
   using Tizen.NUI.UIComponents;
   using Tizen.NUI.BaseComponents;
   using Tizen.NUI.Constants;
   

2. Scope the application to the HelloTest namespace:

   namespace HelloTest
   

3. Derive the application from the Tizen.NUI.NUIApplication class:

   class Example : NUIApplication
   

   The Tizen.NUI.NUIApplication class includes constructors that allow you to create applications with various stylesheets and window modes.

4. To handle behavior when the application is launched, override the OnCreate() method of the Tizen.NUI.NUIApplication class and call the initialization method:

   protected override void OnCreate()
   {
       base.OnCreate();
       Initialize();
   }
   

   Note To invoke the Created event of the Tizen.Applications.Core​Application class, you must call the base.OnCreate() method inside the override.
5. Within the Initialize() method, set the text label properties:
   1. Create the text label object from the Tizen.NUI.BaseComponents.TextLabel class:

      _text = new TextLabel("Hello World");
      

   2. Position the text in the center of the application window. The ParentOrigin property defines a point within the parent view area. If the text label size is not specified, the text label is at least as wide as the screen.

      _text.ParentOrigin = ParentOrigin.CenterLeft;
      

   3. Align the text horizontally to the center of the available area:

      _text.HorizontalAlignment = HorizontalAlignment.Center;
      

   4. To illustrate the label width, set the label background color:

      _text.BackgroundColor = Color.Red;
      

   5. Define the text size in points:

      _text.PointSize = 32.0f;
      

   For more information on the key properties of the Tizen.NUI.BaseComponents.TextLabel class, see TextLabel.

6. Implement the main application window:
   1. Create the window and add an event handler for the TouchEvent event of the Tizen.​NUI.Window class. This event handler is invoked whenever the application window is clicked.

      Window window = Window.Instance;
      window.TouchEvent += WindowTouched;
      

   2. Add the text label to the window’s root layer:

      window.Add(_text);
      

7. Define the event handler to change the label text:

   private void WindowTouched(object sender, Window.TouchEventArgs e)
   {
       _text.Text = "I have been touched!";
   }
   

8. To handle behavior when the window close button is clicked and the application is about to terminate, override the OnTerminate() method of the Tizen.NUI.NUIApplication class:

   protected override void OnTerminate()
   {
       base.OnTerminate();
       _text = null;
   }
   

   Note To invoke the Terminated event of the Tizen.​Applications.Core​Application class, you must call the base.OnTerminate() method inside the override.
9. Implement the Main() method:
   1. Create the application through the default constructor:

      Example example = new Example();
      

   2. Start the application main loop.

      This ensures that images are displayed, and that events and signals are dispatched and captured.

      In this simple tutorial, the Main() method resides within the class. For significant application development, the Main() method must be placed in a separate .cs file.

      example.Run(args);
      

The following example shows the full source code of the tutorial application described above.

using System;
using System.Runtime.InteropServices;
using Tizen.NUI;
using Tizen.NUI.UIComponents;
using Tizen.NUI.BaseComponents;
using Tizen.NUI.Constants;

namespace HelloTest
{
    class Example : NUIApplication
    {
        TextLabel _text;

        protected override void OnCreate()
        {
            base.OnCreate();
            Initialize();
        }

        private void Initialize()
        {
            /// Add a simple text label to the main window
            _text = new TextLabel("Hello World");
            _text.ParentOrigin = ParentOrigin.CenterLeft;
            _text.HorizontalAlignment = HorizontalAlignment.Center;
            _text.BackgroundColor = Color.Red;
            _text.PointSize = 32.0f;

            /// Add the touch signal event handler
            Window window = Window.Instance;
            window.TouchEvent += WindowTouched;

            window.Add(_text);
        }

        /// Event handler for window touched signal
        private void WindowTouched(object sender, Window.TouchEventArgs e)
        {
            _text.Text = "I have been touched!";
        }

        protected override void OnTerminate()
        {
            base.OnTerminate();
            _text = null;
        }

        static void Main(string[] args)
        {
            Example example = new Example();
            example.Run(args);
        }
    }
}