title property
final
This widget is the home page of your application. It is stateful, meaning that it has a State object (defined below) that contains fields that affect how it looks.
This class is the configuration for the state. It holds the values (in this case the title) provided by the parent (in this case the App widget) and used by the build method of the State. Fields in a Widget subclass are always marked "final".
Implementation
final String title;