The lifecycle

The CrossFly lifecycle has three levels: the application, the window (screen), and the component.

Level 1 — application: the bootstrap (Main)

Main is libGDX’s ApplicationListener. When the platform comes up, libGDX calls Main.create() on the paint thread, and Main:

1. detects the platform and initializes the runtime and the device configuration;
2. resolves the name of the main window (from a classname argument or from getMainWindow());
3. instantiates that window by reflection (Class.forName(...) → newInstance()) and calls its onShow().

After that, libGDX calls render() (on each rendered frame) and resize() — always on the paint thread.

Level 2 — window: onShow()

Each screen is a subclass of Window that builds its UI in onShow() (with super.onShow()):

public class TelaHome extends Window {
   @Override public void onShow() throws Exception {
      super.onShow();
      setLayout(new VerticalLayout());
      add(LAY_AUTO, new Label("Início"));
   }
}

Why onShow() and not the constructor? In the constructor, the bounds and hierarchy are not yet ready — Screen.width/height and the window size are only valid afterward. Building the UI too early leads to wrong measurements. (The window stack and navigation are in The window stack.)

Level 3 — component: onAdd(firstTime) / onRemove()

When a component enters the tree, the framework calls onAdd(boolean firstTime); when it leaves, onRemove(). This is where you initialize and release resources:

public class Relogio extends Component {
   private Timer timer;
   @Override public void onAdd(boolean firstTime) throws Exception {
      super.onAdd(firstTime);
      if (firstTime) timer = iniciarTimer();   // resources that must exist only once
   }
   @Override public void onRemove() {
      if (timer != null) timer.cancel();        // always release on exit
      super.onRemove();
   }
}

What does firstTime distinguish? A component can be added, removed, and re-added. firstTime == true only the first time — use it for setup that should not repeat. onRemove() is the cleanup counterpart: cancel timers, listeners, cursors.

General rule: do not initialize UI/resources in the constructor. Use onShow() (window) and onAdd(firstTime) (component), where bounds and hierarchy are already valid.

See also

• Apply: Navigate between screens
• Next: State and data flow