Eine detaillierte Aufschlüsselung der Navigation in Flutter

Flutter wird bei Entwicklern immer beliebter. Die meisten Ansätze zum Erstellen von Anwendungen wurden bereits etabliert und werden täglich bei der Entwicklung von E-Commerce-Anwendungen verwendet. Das Thema Navigation wird auf den Hintergrund oder den dritten Plan reduziert. Welche Navigations-API bietet das Framework? Welche Ansätze wurden entwickelt? Wie werden diese Ansätze verwendet und wozu sind sie gut?

Einführung

Beginnen wir mit dem, was Navigation ist. Die Navigation ist eine Methode, mit der Sie mit bestimmten Parametern zwischen der Benutzeroberfläche navigieren können.

In der IOS-Welt organisiert der UIViewController beispielsweise die Navigation und in Android die Navigationskomponente. Was bietet Flutter?

Navigator

Bildschirme in Flutter werden als Route bezeichnet. Für die Navigation zwischen Routen gibt es eine Navigator-Klasse mit einer umfangreichen API zum Implementieren verschiedener Navigationstypen.

Navigieren zu und Zurückkehren von einer neuen Route

Fangen wir einfach an. Die Navigation zu einem neuen Bildschirm (Route) wird von der push () -Methode aufgerufen, die ein Argument akzeptiert - dies ist Route.

Navigator.push(MaterialPageRoute(builder: (BuildContext context) => MyPage()));

Schauen wir uns den Aufruf der Push-Methode genauer an:

Navigator — , .

Navigator.push() — route   .

MaterialPageRoute() — route,   .

builder — MaterialPageRoute, .

MyPage — Stateful/Stateless Widget

route

pop().

Navigator.pop();

builder . Navigator, build.

Navigator.push(context, MaterialPageRoute(builder: (context) => MyPage(someData: data)));

MyPage ( ).

pop() .

Navigator.pop(data);

Navigator State

Navigator, MaterialApp/CupertinoApp/WidgetsApp. State API .

Stack. "call flow" NavigatorState.

vs

. route, .

:

, — ?

: , . .

, — ?

: , .

Imperative vs Declarative Programming

. . Route. Flutter route, MaterialPageRoute CupertinoPageRoute. CupertinoPageRoute title, settings.

:

Navigator.push(
    context,
    CupertinoPageRoute<T>(
        title: "Setting",
        builder: (BuildContext context) => MyPage(),
        settings: RouteSettings(name:"my_page"),
    ),
);

route   ViewModel/Controller/BLoC/… .

MyPage CupertinoPageRoute. push .

:

, route .

. .

:

Navigator.pushNamed(context, '/my_page');

. " " .

MaterialApp/CupertinoApp/WidgetsApp. 2 onGenerateRoute onUnknownRoute .

:

MaterialApp(
    onUnknownRoute: (settings) => CupertinoPageRoute(
      builder: (context) {
                return UndefinedView(name: settings.name);
            }
    ),
  onGenerateRoute: (settings) {
    if (settings.name == '\my_page') {
      return CupertinoPageRoute(
                title: "MyPage",
                settings: settings,
        builder: (context) => MyPage(),
      );
    }
        //     
  },
);

:

onGenerateRoute — Navigator.pushNamed(). route.

onUnknownRoute — onGenerateRoute null. route, web — 404 page.

. , .

. .

:

• showAboutDialog
• showBottomSheet
• showDatePicker
• showGeneralDialog
• showMenu
• showModalBottomSheet
• showSearch
• showTimePicker
• showCupertinoDialog
• showDialog
• showLicensePage
• showCupertinoModalPopup

. API, .

?

, showGeneralDialog.

:

Future<T> showGeneralDialog<T>({
  @required BuildContext context,
  @required RoutePageBuilder pageBuilder,
  bool barrierDismissible,
  String barrierLabel,
  Color barrierColor,
  Duration transitionDuration,
  RouteTransitionsBuilder transitionBuilder,
  bool useRootNavigator = true,
  RouteSettings routeSettings,
}) {
  assert(pageBuilder != null);
  assert(useRootNavigator != null);
  assert(!barrierDismissible || barrierLabel != null);
  return Navigator.of(context, rootNavigator: useRootNavigator).push<T>(_DialogRoute<T>(
    pageBuilder: pageBuilder,
    barrierDismissible: barrierDismissible,
    barrierLabel: barrierLabel,
    barrierColor: barrierColor,
    transitionDuration: transitionDuration,
    transitionBuilder: transitionBuilder,
    settings: routeSettings,
  ));
}

. showGeneralDialog push NavigatorState _DialogRoute(). , .

— route .

route

 "every thins is a route", . , route .

route Flutter — PageRoute PopupRoute.

PageRoute — route, .

PopupRoute — route, route.

PageRoute:

• MaterialPageRoute
• CupertinoPageRoute
• _SearchPageRoute
• PageRouteBuilder

PopupRoute:

• _ContexMenuRoute
• _DialogRoute
• _ModalBottomSheetRoute
• _CupertinoModalPopupRoute
• _PopupMenuRoute

PopupRoute , .

:

, .

Best practices

, " ?". , API , . .

:

• .
• BuildContext ( , BuildContext).
• . route, CupertinoPageRoute, BottomSheetRoute, DialogRoute ..

:

abstract class IRouter {
  Future<T> routeTo<T extends Object>(RouteBundle bundle);
  Future<bool> back<T extends Object>({T data, bool rootNavigator});
  GlobalKey<NavigatorState> rootNavigatorKey;
}

:

routeTo - .

back — .

rootNavigatorKey — GlobalKey NavigatorState.

, .

class Router implements IRouter {
    @override
  GlobalKey<NavigatorState> rootNavigatorKey = GlobalKey<NavigatorState>();

    @override
  Future<T> routeTo<T>(RouteBundle bundle) async {
   // Push logic here
  }

    @override
  Future<bool> back<T>({T data, bool rootNavigator = false}) async {
        // Back logic here
    }
}

 , routeTo().

@override
  Future<T> routeTo<T>(RouteBundle bundle) async {
        assert(bundle != null, "The bundle [RouteBundle.bundle] is null");
    NavigatorState rootState = rootNavigatorKey.currentState;
    assert(rootState != null, 'rootState [NavigatorState] is null');

    switch (bundle.route) {
      case "/routeExample":
        return await rootState.push(
          _buildRoute<T>(
            bundle: bundle,
            child: RouteExample(),
          ),
        );

      case "/my_page":
        return await rootState.push(
          _buildRoute<T>(
            bundle: bundle,
            child: MyPage(),
          ),
        );
      default:
        throw Exception('Route is not found');
    }
  }

root NavigatorState ( WidgetsApp) push RouteBundle .

RouteBundle. , .

enum ContainerType {
  /// The parent type is [Scaffold].
  ///
  /// In IOS route with an iOS transition [CupertinoPageRoute].
  /// In Android route with an Android transition [MaterialPageRoute].
  ///
  scaffold,

  /// Used for show child in dialog.
  ///
  /// Route with [DialogRoute].
  dialog,

  /// Used for show child in [BottomSheet].
  ///
  /// Route with [ModalBottomSheetRoute].
  bottomSheet,

  /// Used for show child only.
  /// [AppBar] and other features is not implemented.
  window,
}
class RouteBundle {
  /// Creates a bundle that can be used for [Router].
  RouteBundle({
    this.route,
    this.containerType,
  });

  /// The route for current navigation.
  ///
  /// See [Routes] for details.
  final String route;

  /// The current status of this animation.
  final ContainerType containerType;
}

enum ContainerType — , .

RouteBundle — - route.

_buildRoute. , route .

Route<T> _buildRoute<T>({@required RouteBundle bundle, @required Widget child}) {
    assert(bundle.containerType != null, "The bundle.containerType [RouteBundle.containerType] is null");

    switch (bundle.containerType) {
      case ContainerType.scaffold:
        return CupertinoPageRoute<T>(
          title: bundle.title,
          builder: (BuildContext context) => child,
          settings: RouteSettings(name: bundle.route),
        );
      case ContainerType.dialog:
        return DialogRoute<T>(
          title: '123',
          settings: RouteSettings(name: bundle.route),
          pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) {
                        return child;
                    },
        );
      case ContainerType.bottomSheet:
        return ModalBottomSheetRoute<T>(
          settings: RouteSettings(name: bundle.route),
          isScrollControlled: true,
          builder: (BuildContext context) => child,
        );
      case ContainerType.window:
        return CupertinoPageRoute<T>(
          settings: RouteSettings(name: bundle.route),
          builder: (BuildContext context) => child,
        );
      default:
        throw Exception('ContainerType is not found');
    }
  }

ModalBottomSheetRoute DialogRoute, . route Material Flutter.

back.

@override
Future<bool> back<T>({T data, bool rootNavigator = false}) async {
    NavigatorState rootState = rootNavigatorKey.currentState;
  return await (rootState).maybePop<T>(data);
}

rootNavigatorKey App :

MaterialApp(
    navigatorKey: widget.router.rootNavigatorKey,
    home: Home()
);

, route. - "" , , Dependency Injection.

router.routeTo(RouteBundle(route: '/my_page', containerType: ContainerType.window));

, :

• BuildContext GlobalKey
• route View

Flutter , .

:



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