Event sent when the screen controller and all its declaratively defined components are created, and dependency
injection is completed. Nested fragments are not initialized yet. Some visual components are not fully
initialized, for example buttons are not linked with actions.
In this event listener, you can create visual and data components, for example:
@Subscribe
protected void onInit(InitEvent event) {
Label<String> label = uiComponents.create(Label.TYPE_STRING);
label.setValue("Hello World");
getWindow().add(label);
}