The Java Color Picker was a project created for Comptuer Languages and Implemention course. The project demonstrates use of Java, Java File I/O, and the Swing User Interface library to create a Color Sampler application. The application uses the Model-View-Controller (MVC) Design Pattern to encapsulate the application's business logic and user interface componenets for maintainability of the application. Figure 1 represents a comparison between tasked assignment and developed application.

Fig. 1. Side-by-side comparison of described homework problem and developed application.

The business logic of the application is encapsulated within the application_model class and user interface components are encapsulated in the application_view class. For now on within the documentation the business logic will be referred as Model and the user interface components will be referred as View. The application_controller class is used by the View and Model to communicate events between the two classes. Figure 2 represents the relationship between the three classes.

Fig. 2. UML of the application.

Components the View wishes to open to the Model for processing of events such as mouse-clicks must be exposed through getter methods. Once the View component is exposed, the component must be registered with the application's application_controller class in which the event is defined with the event behaviour. The event behaviour is defined by a called method within the application Model. Every time a event occurs such as a mouse-click, the appropriate function from Model is called. Model data changed must be reflected within the View by updating relevant View component(s) within the defined event behaviour.

When a mouse-click for increasing the blue value via the "+" button occurs the application_controller calls the appropriate registered event behaviour withing the class being make_blue_lighter() function. Within the function make_blue_lighter(), the appropriate function from the Model to change RGB data and increase the blue value is model.increment_blue().

The View must reflect changes from the Model data. The registered event behaviour uses the getter methods to acquire the necssary exposed components of the View which in this includes: the main window, the color viewer, and the blue textfield value. The Controller calls upon view.get_main_window(),view.get_color_viewer(), and view.get_bluePalette_field() to do the conduct the necessary visual changes to the user interface.

Figure 3 shows the process of reacting to a user initiating a mouse-click on a button to increase the blue value in the Color Sampler.

void make_blue_lighter() {

  // Update the blue value within the Model data.
  model.increment_blue();
  
  // Update window title bar to show new text.
  view.get_main_window().setTitle(model.update_window_title());
  // Update color viewer to display new color.
  view.get_color_viewer().setBackground(new Color(model.get_preview_color().get_red(), model.get_preview_color().get_green(), model.get_preview_color().get_blue()));
  // Update text field to show new blue value.
  view.get_bluePalette_field().setText(String.valueOf(model.get_preview_color().get_blue()));

}

Fig. 3. The defined registered event behaviour wtihin the Controller class.