Event Handling

MicroUI generates integer-based events that encode the low-level input type and some data. The application can handle these events in the handleEvent() method.

The handleEvent Method

• Every class that extends Widget inherits the handleEvent() method.

• Add custom event handling by overriding the handleEvent() method of a widget.

• As an example, here is the event handling of the Button class:

  @Override
  public boolean handleEvent(int event) {
          int type = Event.getType(event);
          if (type == Pointer.EVENT_TYPE) {
                  int action = Pointer.getAction(event);
                  if (action == Pointer.PRESSED) {
                          setPressed(true);
                  } else if (action == Pointer.RELEASED) {
                          setPressed(false);
                          handleClick();
                          return true;
                  }
          } else if (type == DesktopEventGenerator.EVENT_TYPE) {
                  int action = DesktopEventGenerator.getAction(event);
                  if (action == PointerEventDispatcher.EXITED) {
                          setPressed(false);
                  }
          }
          return super.handleEvent(event);
  }
  

• It’s important to note that only widgets that are “enabled” will receive input events. One can enable a widget by calling setEnabled(true).

• In the Button class, the click triggers an action defined by the registered OnClickListener.

Using Events with Buttons

As an example of usage of the Button class we reuse the code created in the previous step, and add a simple action to the button by adding a OnClickListener.

button.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick() {
        System.out.println("Clicked!");
    }
});

When running the modified sample, this is shown in the console:

=============== [ Initialization Stage ] ===============
=============== [ Converting fonts ] ===============
=============== [ Converting images ] ===============
=============== [ Launching on Simulator ] ===============
Clicked!
Clicked!
Clicked!
Clicked!
Clicked!

Next step: Fonts