theseus_navigator

Description:

theseus navigator

Theseus Navigator #
  
Theseus Navigator package aims to simplify implementing a navigation in your app, and supports the following features:

Declarative navigation scheme
Strongly-typed parameters
Deep links
Nested navigation
Dynamic upward navigation
Redirections
Persisting of navigation state
Common navigation widgets

It provides a simple API, does not require code generation and uses Flutter's Router / Navigator 2.0 under the hood.

Note: The package is still in progress, and APIs might change. Any feedback, like missing features, better API suggestions, bug reports and other is appreciated.
You can check all supported features in the Theseus Navigator Demo app.
Overview #
The starting point of using Theseus Navigator is to define your app's navigation scheme.
It might look like this:

Destinations defines all possible UI endpoints in your app that users could reach using navigation.
NavigationController is responsible for managing the app navigation state within the scope of its destinations. It performs navigation actions, like goTo(destination) and goBack(), and builds the navigation stack.
The NavigationScheme is an entry point to navigation, it orchestrates all destinations and navigation controllers. It has a root navigation controller that manages top-level destinations, and, optionally, additional navigators to support nested navigation.
Here is an example of usage:

Define destinations and navigation scheme

final homeDestination = Destination(
path: 'home',
isHome: true,
builder: (context, parameters) => HomeScreen(),
);
final catalogDestination = Destination(
path: 'catalog',
builder: (context, parameters) => CatalogScreen(),
);
final settingsDestination = Destination(
path: 'settings',
builder: (context, parameters) => SettingsScreen(),
);
final navigationScheme = NavigationScheme(
destinations: [
homeDestination,
catalogDestination,
settingsDestination,
],
);
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Setup a Router with your navigation scheme

@override
Widget build(BuildContext context) {
return MaterialApp.router(
//...
routerConfig: navigationScheme.config,
);
}
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Somewhere in the app to navigate

onTap: () => navigationScheme.goTo(ordersDestination)
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Destination #
The Destination is a model of UI endpoint that user can navigate in your app.
Generally, you define a destination like this:
final homeDestination = Destination(
path: 'home',
builder: (context, parameters) => HomeScreen(),
);
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It is a final destination, which directly displays the content returned by provided builder function.
Nested navigation
For nested navigation, instead of builder parameter you should provide a navigator, which is a NavigationController.
It manages its own destinations, which could be either final ones and build the content or transit ones and provide another nested navigator.
final mainDestination = Destination(
path: '/',
navigator: mainNavigator,
);

final mainNavigator = NavigationController(
destinations:[
homeDestination,
catalogDestination,
settingsDestination,
],
);
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The NavigatorController is described in next sections.
By using Destination.transit() constructor it is also possible to wrap the nested navigation UI in some additional widget subtree.
final mainDestination = Destination.transit(
path: '/',
navigator: mainNavigator,
builder: (context, parameters, childBuilder) {
return Column(
children: [
const Text('Parent destination'),
Expanded(child: childBuilder(context)),
],
);
}
);
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This constructor has an optional builder parameter with additional childBuilder argument, which represents the nested content and must be included in the resulting widget tree.
Path
The destination is defined by its uri, which is built from the destination path and parameters.
The path might contains placeholders for path parameters. The last path parameter is optional. Arbitrary query parameters are also supported.
Example of destination path:
/categories/{categoryId}
The following specific URIs will match that destination path:
/categories
/categories/1
/categories?q=someQuery
/categories/1?q=someQuery
Two last URIs contains a query parameter as well, and still match the specified destination path.
Parameters
Default parameters handling
By default, destination parameters, both path and query, are extracted from the destination's URI into the DestinationParameters class. It stores them as Map<String, String>.
In this case you don't need specify a destination parser, the DefaultDestinationParser implementation is used implicitly.
final categoriesDestination = Destination(
path: 'categories',
builder: (context, params) => CategoryListScreen(
parentCategoryId: params?['parentId'],
),
);
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For example above, the following URI categories?parentId=2 would be parsed to a destination object that would build a CategoryListScreen with parentCategoryId: 2.
Custom type parameters
To use destination parameters of a certain type, you have to do the following:

Create a class that extends DestinationParameters like this:

class CategoriesDestinationParameters extends DestinationParameters {
CategoriesDestinationParameters({
this.parentCategory,
}) : super();

final Category? parentCategory;
}
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Implement destination parser specific for your parameters type:

class CategoriesDestinationParser extends DestinationParser<CategoriesDestinationParameters> {
CategoriesDestinationParser({
required this.categoryRepository,
});

final CategoryRepository categoryRepository;

@override
Future<CategoriesDestinationParameters> parametersFromMap(Map<String, String> map) async {
final category = await categoryRepository.getCategory(map['parentCategoryId'] ?? '');
return CategoriesDestinationParameters(
parentCategory: category,
);
}

@override
Map<String, String> parametersToMap(CategoryListParameters parameters) {
final result = <String, String>{};
if (parameters.parentCategory != null) {
result['parentCategoryId'] = parameters.parentCategory!.id;
}
return result;
}
}
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After that you will create your destination like:

final categoriesDestination = Destination<CategoriesDestinationParameters>(
path: 'categories',
builder: (context, params) => CategoryListScreen(
parentCategory: params?.parentCategory,
),
parser: CategoriesDestinationParser(
categoryRepository: CategoryRepository(),
),
);
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Settings
The DestinationSettings contains attributes that are used to determine a logic and behavior of updating the navigation state with the destination.
transitionMethod - defines how the navigation stack will be changed on navigation to the destination, can be push or replace.
transition - animations that would apply when the destination content appears, can be material, custom, or none.
In case of custom transition, you have to provide transitionBuilder as well.
There are two pre-defined factory methods:

material() - returns a settings to pushes a destination to the stack with a standard Material animations.
dialog() - display a destination as a modal dialog.
quite() - replace the current destination with a new one without any animations.

final catalogDestination = Destination(
path: 'catalog',
builder: (context, parameters) => CatalogScreen(),
settings: const DestinationSettings.quiet(),
);
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NavigationController #
The NavigationController is a core component of the package, which manages the state of navigation.
It maintains the navigation stack of destinations and offers methods to update it, like goTo(destination) and goBack().
Navigation controller is a ChangeNotifier, and notifies the NavigationScheme on any update of its navigation stack.
You have an access to the whole navigation stack, and to the top most destination in the stack using currentDestination property.
This example shows creation of the navigator that would wrap destinations with standard Flutter's Navigator widget:
final mainNavigator = NavigationController(
destinations: [
homeDestination,
catalogDestination,
settingsDestination,
],
tag = 'Main',
);
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The tag attribute value is used as a key of the Navigator widget, and also allows to find logs related to this NavigationController instance.
Navigator Builder
NavigationController allows you to wrap destinations with your custom navigation UI.
This is required when you would like to navigate destinations through the BottomNavigationBar, TabBar, Drawer or some other way.
To do this, you have to extend the NavigatorBuilder class and override its build method:
class CustomNavigatorBuilder extends NavigatorBuilder {
const CustomNavigatorBuilder() : super();

@override
Widget build(BuildContext context, NavigationController navigator) {
// Your implementation of wrapper widget is here.
// You have an access a navigator's stack and current destination.
}
}
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Then you should specify the builder in the navigator instance:
final mainNavigator = NavigationController(
destinations: [
homeDestination,
catalogDestination,
settingsDestination,
],
builder: CustomNavigatorBuilder(),
tag: 'Main',
);
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Navigation via Bottom navigation bar, Drawer and Tab bar
The package includes implementations of NavigatorBuilder for most common cases:

BottomNavigationBuilder - uses Flutter's Scaffold with BottomNavigationBar or Material 3 NavigationBar to wrap the current destination content and to switch destinations.
DrawerNavigationBuilder - allows to navigate using Drawer widget.
TabsNavigationBuilder - uses TabBar to navigate destinations

fore example, adding the bottom navigation to your app is simple as following:
final navigationScheme = NavigationScheme(
navigator: NavigationController(
destinations: [
homeDestination,
catalogDestination,
settingsDestination,
],
builder: BottomNavigationBuilder(
bottomNavigationItems: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.home_rounded),
label: 'Home',
),
BottomNavigationBarItem(
icon: Icon(Icons.list_rounded),
label: 'Catalog',
),
BottomNavigationBarItem(
icon: Icon(Icons.more_horiz_rounded),
label: 'Settings',
),
],
),
tag = 'Main',
),
);
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The styling of the BottomNavigationBar widget is supported by using optional parameters argument of the BottomNavigationBuilder.
You can use DrawerNavigationBuilder and TabsNavigationBuilder the same way.
Upward navigation
Sometimes, on reverse navigation from a destination that user accessed bypassing underlay destinations, we need to restore a missed destination hierarchy.
For example, user open an app by a deep link that leads to a category screen somewhere in the categories hierarchy. On navigating back from this screen we would like to show the upper level category screen, and so on until the root of categories.
The package support this behavior, when you define upwardDestinationBuilder parameter of destination.
It might look like this:
final categoriesDestination = Destination<CategoryListParameters>(
path: 'categories',
builder: (context, params) => CategoryListScreen(
parentCategory: params?.category,
),
upwardDestinationBuilder: (destination) =>
destination.parameters?.parentCategory == null
? null
: destination.copyWithParameters(CategoriesDestinationParameters(
parentCategory:
destination.parameters?.parentCategory!.parent)),
parser: CategoriesDestinationParser(
categoryRepository: CategoryRepository(),
),
);
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Deep-links #
When a destination is requested by a platform, the following is happened for each navigator in the hierarchy from the current destination up to the root:


Current destination is updated according to requested deep-link destination.


If the upwardDestinationBuilder parameter is provided for the current destination, the navigator's stack is cleared before adding new destination. Otherwise the current destination is pushed to existing stack.


Redirections #
Sometimes we need to redirect user to another screen before displaying the requested content.
The basic example is that some screen should be shown only for signed in users.
The package provides Redirection class to support this behavior. You can specify a list of redirections for destinations that should be validated before navigation.
final settingsDestination = Destination(
path: 'settings',
builder: (context, parameters) => SettingsScreen(),
redirections: [
Redirection(
validator: (destination) => SynchronousFuture(isLoggedIn),
destination: loginDestination,
)
]
);
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In the example above, when the user navigates to Settings screen, first the validator function of specified redirection will be called. If it return false, then user will be redirected to the Login screen.
Validator function in redirection could be asynchronous. In case it runs for a long time, the waiting overlay widget is displayed until the destination resolved. You can customize the waiting overlay by providing waitingOverlayBuilder parameter of NavigationScheme.
It is also possible to dynamically identify a destination for redirection by providing resolver function instead of fixed destination.
Error handling #
If the errorDestination is specified in the NavigationScheme, user wil be redirected to this destination when trying to navigate to nonexistent screen.
final navigationScheme = NavigationScheme(
destinations: [
//...
],
errorDestination: Destination(
path: '/error',
builder: (context, parameters) => ErrorScreen(),
)
);
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The following errors are currently supported:

Navigation to a destination that is not in the NavigationScheme (requested destination path does not match any destination in the scheme)
The requested destination is found in the scheme, but its parameters could not be resolved by the destination's parser.

Other #
Examples
For more detailed code samples, please see the example project which contains the working demo app.
Useful Links
Material Design - Understanding Navigation
Routing packages research report