Advanced Styling

Using Images in Stylesheet

  • Let’s add a button to the application, with the MicroEJ logo as background.
  • Since this background will apply to a specific button, introduce a new class selector that will select this button.

Class Selector

  • Just like a class in CSS, it associates to every element that is from the same class.

  • Define a class for the button as follows:

    private static final int BUTTON = 600;
    
  • Bind the class BUTTON to the button widget:

    Button button = new Button("Click ME");
    button.addClassSelector(BUTTON);
    
  • Retrieve the style for this class from the stylesheet and edit the attributes:

    EditableStyle style = css.getSelectorStyle(new ClassSelector(BUTTON));
    
  • Finally, lets add an Image Background to this Button:

    style.setBackground(new ImageBackground(Image.getImage("/images/microej_logo.png")));
    
  • And the result should be as follows:

    public class Main {
       private static final int BUTTON = 600;
    
       public static void main(String[] args) {
          MicroUI.start();
          Desktop desktop = new Desktop();
          Button button = new Button("Click ME");
          button.addClassSelector(BUTTON);
    
          Flow flow = new Flow(LayoutOrientation.VERTICAL);
          flow.addChild(button);
    
          CascadingStylesheet css = new CascadingStylesheet();
          EditableStyle style = css.getSelectorStyle(new ClassSelector(BUTTON));
          style.setBackground(new ImageBackground(Image.getImage("/images/microej_logo.png")));
    
          desktop.setStylesheet(css);
          desktop.setWidget(flow);
          desktop.requestShow();
       }
    }
    
../../_images/imagebackgroundexample.png

Combinator and Conditional Style

  • It is possible to combine two or more selectors using combinators.

  • In this example the active state of the button will turn the text blue.

    CascadingStylesheet css = new CascadingStylesheet();
    Selector buttonSelector = new ClassSelector(BUTTON);
    EditableStyle style = css.getSelectorStyle(buttonSelector);
    style.setBackground(new ImageBackground(Image.getImage("/images/microej_logo.png")));
    Selector activeSelector = new StateSelector(Button.ACTIVE);
    EditableStyle styleActive = css.getSelectorStyle(new AndCombinator(buttonSelector, activeSelector));
    styleActive.setColor(Colors.BLUE);
    
  • The class selector for the button has been extracted as a locale to be combined with the button active state selector.

../../_images/classselectorexample.png