initState method

  1. @override
void initState ()

Called when this object is inserted into the tree.

The framework will call this method exactly once for each State object it creates.

Override this method to perform initialization that depends on the location at which this object was inserted into the tree (i.e., context) or on the widget used to configure this object (i.e., widget).

If a State's build method depends on an object that can itself change state, for example a ChangeNotifier or Stream, or some other object to which one can subscribe to receive notifications, then be sure to subscribe and unsubscribe properly in initState, didUpdateWidget, and dispose:

If you override this, make sure your method starts with a call to super.initState().


void initState() {
  for (NavigatorObserver observer in widget.observers) {
    assert(observer.navigator == null);
    observer._navigator = this;
  String initialRouteName = widget.initialRoute ?? Navigator.defaultRouteName;
  if (initialRouteName.startsWith('/') && initialRouteName.length > 1) {
    initialRouteName = initialRouteName.substring(1); // strip leading '/'
    assert(Navigator.defaultRouteName == '/');
    final List<Route<dynamic>> plannedInitialRoutes = <Route<dynamic>>[
      _routeNamed<dynamic>(Navigator.defaultRouteName, allowNull: true, arguments: null),
    final List<String> routeParts = initialRouteName.split('/');
    if (initialRouteName.isNotEmpty) {
      String routeName = '';
      for (String part in routeParts) {
        routeName += '/$part';
        plannedInitialRoutes.add(_routeNamed<dynamic>(routeName, allowNull: true, arguments: null));
    if (plannedInitialRoutes.last == null) {
      assert(() {
              'Could not navigate to initial route.\n'
              'The requested route name was: "/$initialRouteName"\n'
              'There was no corresponding route in the app, and therefore the initial route specified will be '
              'ignored and "${Navigator.defaultRouteName}" will be used instead.'
        return true;
      push(_routeNamed<Object>(Navigator.defaultRouteName, arguments: null));
    } else {
      plannedInitialRoutes.where((Route<dynamic> route) => route != null).forEach(push);
  } else {
    Route<Object> route;
    if (initialRouteName != Navigator.defaultRouteName)
      route = _routeNamed<Object>(initialRouteName, allowNull: true, arguments: null);
    route ??= _routeNamed<Object>(Navigator.defaultRouteName, arguments: null);
  for (Route<dynamic> route in _history)