attach method
Attaches a new widget by creating its transition state and triggering animation.
Implementation
void attach(Widget widget) {
final T newState = createState(widget);
if (states.isEmpty) {
context.initialAnimation
? newState.fadeIn()
: newState.ensureFadeInCompleted();
} else {
// Subsequent widgets: always fade-in animation.
newState.fadeIn();
}
states[widget.key!] = newState;
}