registerScreen method
void
registerScreen()
Call registerScreen multiple times to specify the relationship between
screenKey and screens built by the WidgetBuilder
Implementation
void registerScreen(AFScreenID screenKey, AFConnectedUIBuilderDelegate screenBuilder, AFScreenConfig config) {
assert(_isValidBuilder<AFConnectedScreen>(screenBuilder));
_screens[screenKey] = screenBuilder;
_screenConfigs[screenKey] = config;
}