advanced_navigator 0.1.2+1
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Flutter's Navigator 2.0 as one easy-to-use widget with full page history manipulation operations, simplified pop event delegation and powerful nesting.

Advanced Navigator pub package license

This package aims at bringing the powerful capabilities of Navigator 2.0 to any Flutter app as one easy-to-use widget. The focus was to keep this package simple and familiar to people used to the standard navigator API while at the same time providing even low level customizability for very difficult and unusual navigation logic.


Quick Start #

To get started, create a MaterialApp or CupertinoApp and return an instance of AdvancedNavigator from its builder function:

MaterialApp(
  builder: (context, _) => AdvancedNavigator(
    ...
  ),
);

In the next step, create a map with your desired URIs for your app:

AdvancedNavigator(
  paths: {
    '/': (_) => [
      MaterialPage(key: ValueKey('home'), child: ViewHome()),
    ],
    '/followers': (_) => [
      MaterialPage(key: ValueKey('home'), child: ViewHome()),
      MaterialPage(key: ValueKey('followers'), child: ViewFollowers()),
    ],
    '/followers/{userId}': (args) => [
      MaterialPage(key: ValueKey('home'), child: ViewHome()),
      MaterialPage(key: ValueKey('followers'), child: ViewFollowers()),
      MaterialPage(key: ValueKey('profile${args['userId']}'), child: ViewProfile(args['userId'])),
    ],
  },
),

Now, you can open these paths from anywhere in your app with AdvancedNavigator.openNamed(context, <uri>). (see Paths)

Similarly, you can define named pages which can be pushed to and popped from the top of the navigators page stack with AdvancedNavigator.pushNamed(context, <page name>) and AdvancedNavigator.pop(context) respectively. (see Pages)

Examples #

URL syncing #

In this example, the navigators page stack will always stay in sync with the browsers url.

The following snippet is all you need for implementing the above navigation logic.

AdvancedNavigator(
  paths: {
    '/': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
    ],
    '/items': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
    ],
    '/items/{itemId}': (args) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
      CupertinoPage(key: ValueKey('item${args['itemId']}'), child: ViewItem(int.parse(args['itemId']))),
    ],
  },
);

This is how the navigation is performed from the list tile:

ListTile(
  ...
  onPressed: () => AdvancedNavigator.openNamed(context, '/items/$itemId');
),

Persistent Side Drawer #

// TODO

Encapsulated Navigation #

// TODO (view code)

Documentation #

This package is build to handle both, simple navigations without unnecessary code overhead as well as very complex navigations which require web-URL synching across nested navigators. At its core is the AdvancedNavigator widget. It looks similar to the standard navigator but provides easy access to the declarative API and adds other features without requiring custom router delegates or route information providers.

Overview #

Every navigation operation which can be applied to AdvancedNavigatior falls into one of three categories:

  1. Path Navigation: Replaces entire page stack with new list of pages
  2. Page Navigation: Adds or removes page to or from top of page stack
  3. Pageless Navigation: Attaches route to top-most page in page stack

A page is a blueprint for building a route. For more information, please go to the Navigator 2.0 introduction here.

Furthermore, a path navigations operation performed at a given navigator can also update the navigation state of all navigators nested inside it. This makes for a very useful pattern as it allows an app to be split into multiple loosely connected modules, each with their own navigator. When put together, the navigators will communicate with each other to function as one. (see Nesting)

Paths #

Paths are in most cases declared through the paths argument which provides a simple and clear interface for fully customizable page stack manipulations. It maps a set of URIs to path builder functions which will be invoked whenever AdvancedNavigator.openNamed(context, <uri>) with the associated URI is called. The returned path (list of pages) then replaces the navigators current page stack.

AdvancedNavigator expects each requested path name to be in the standard URI format and will parse it as such. Therefore, to take full advantage of this widget it is recommended to design path names with that format in mind.

There is built in argument parsing for extracting arguments such as id's directly from the provided URI. In the path name, arguments are marked with enclosing parentheses .../{argName}/... and can be read from the args argument in the path builder function to be used for building the page stack.

Query parameters as in /search?q=unicorn&res=50 will be extracted and passed on as well. However, path name arguments will take precidence in the event of a name collision.

AdvancedNavigator(
  paths: {
    '/': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
    ]
    '/items': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
    ],
    // example: '/items/ac9f0e80'
    '/items/{itemId}': (args) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
      CupertinoPage(key: ValueKey('item${args['itemId']}'), child: ViewItem(args['itemId']),
    ],
    // example: '/search?q=unicorn&res=50'
    '/search': (args) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
      CupertinoPage(key: ValueKey('search'), child: ViewSearch(args['q'], res: int.parse(args['res']))),
    ],
  }
);

It is worth noting that most use-cases will only need the paths argument for Path Navigation. However, there is the option to specify an onGeneratePath and onUnknownPath function for full customizability. These functions can work in tandem with paths and are used by the navigator as a fallback for requests paths is unable to handle.

AdvancedNavigator(
  onGeneratePath: (RouteInformation configuration) {
    // code here
  },
  onUnknownPath: (RouteInformation configuration) {
    // fallback code here
  }
),

Pages #

Page Navigation is more generative and can be implemented using the pages argument. Instead of replacing the entire page stack, pages are incrementally added to or removed from the top of the page stack. This allows for very long and flexible page histories but is also less predictable and might lead to undesired navigation flows.

paths defines a map of pages uniquely identified by a string (page name). Also, the string identifier is not required to comply with any format and can be chosen arbitrarily. Arguments are not contained in the name but are passed along as a separate parameter in the pushNamed() function. Calling pushNamed() will invoke the page builder function of the associated page name with the given arguments and add the returned page to the top of the page stack.

Example:

AdvancedNavigator(
  pages: {
    'post': (args) => CupertinoPage(key: ValueKey('post${args['postId']}'), child: ViewPost(args['postId'])),
    'profile': (args) => CupertinoPage(key: ValueKey('profile${args['userId']}'), child: ViewProfile(args['userId'])),
  }
);

Just like paths, pages can also be generated using generator functions. Correspondingly, they are being used as a fallback for named pages from the aforementioned pages map:

AdvancedNavigator(
  onGeneratePage: (RouteSettings configuration) {
    // code here
  },
  onUnknownPage: (RouteSettings configuration) {
    // fallback code here
  },
);

Important: Always be sure to assign a restorable key to every page before adding it to the page stack. Otherwise, there will be issues with path navigation operations as the navigator won't be able to tell whether a page has already been in the page stack before the request was made or not.

Routes #

Routes work nearly identical to pages, however with the difference that they are added to the navigator as a pageless route. Since they have not been inflated from a page, there is no page to be added to the page stack. Instead, they are attached to the current top-most page. Consequently, whenever that page is moved around the page stack or removed, so will this route.

Often it makes more sense to use pages instead as it leaves the app with more fine grained control over the navigator's route stack. However, routes with strict links to the last page such as dialogs and drop-down menus do benefit from being pageless.

Routes can be generated using the onGenerateRoute function and are added using attach() or attachNamed().

AdvancedNavigator(
  onGenerateRoute: (RouteSettings configuration) {
    // code here
  },
  onUnknownRoute: (RouteSettings configuration) {
    // fallback code here
  },
),

The advanced navigator implements an imperative API for remotely manipulating the page stack from anywhere in the widget tree. This new API exposes the following endpoints:

EndpointDescription
openReplaces current page stack with provided page stack
openNamedChecks if provided path name has reference in paths argument, otherwise generates path with onGeneratePath and replaces current page stack.
pushAdds provided page to top of page stack.
pushNamedChecks if provided page name has reference in pages argument and adds page to top of page stack.
attachAttaches provided pageless route to top-most paged route (= Navigator.push).
attachNamedGenerates route with onGenerateRoute and attaches it to top-most paged route (= Navigator.pushNamed).
popPops top-most route from navigator, regardless of whether route is pageless or not. If the navigator only has one route in its stack, the pop request is automatically forwarded to the nearest ancestor.

Since AdvancedNavigator also builds a standard Navigator as its child, all navigation operations from the old imperative API such as Navigator.popAndPushNamed(context, ...) will continue to work with AdvancedNavigator.

In practice, these functions can be invoked by calling them on an instance of AdvancedNavigatorState which can be obtained using AdvancedNavigator.of(context), assuming context contains an instance of AdvancedNavigator.

TextButton(
  child: ...,
  onPressed: () => AdvancedNavigator.of(context).openNamed('items/$itemId'),
),

Equally valid is this, more concise syntax where the context is passed directly to the navigation function:

TextButton(
  child: ...,
  onPressed: () => AdvancedNavigator.openNamed(context, 'items/$itemId'),
),

The of() function also provides the option to specify a skip parameter which allows you to access navigators which are further up in the widget tree above other navigators without having to pass down the build context.

Nesting #

AdvancedNavigator is built to be nested. It configures itself automatically based on whether there is an instance of AdvancedNavigator above itself in the widget tree and also maintains an active channel of communication with its parent navigator throughout its lifetime. This allows AdvancedNavigator to support global URI navigation, even across nested navigators.

To implement nested navigation, path names building nested navigators must be marked as nested by appending /... to the path name. That way, they are matched as a prefix against incoming path name requests and only need to match the first n segments and not the entire path name to the last segment. When then a navigator is unable to fully handle a navigation request, i.e. the requested path name matched a nested path name as longest name, it handles the request with the nested path and stores the remaining unused path segments. Now, other navigators (usually descendants) can set that navigator as their parent and listen to changes on that path remainder and open that path. Vice verca, when a navigation operation occurs in a navigatior which has a parent, that navigator updates the parent's nested path so it can then update its parent or the system navigator of the navigation.

Here is what that means in practice:

AdvancedNavigator(
  paths: {
    '/': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
    ],
    '/myArticles': (_) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
      CupertinoPage(key: ValueKey('myArticles'), child: ViewMyArticles()),
    ],
    '/myArticles/{articleId}/...': (args) => [
      CupertinoPage(key: ValueKey('home'), child: ViewHome()),
      CupertinoPage(key: ValueKey('myArticles'), child: ViewMyArticles()),
      CupertinoPage(key: ValueKey('article${args['articleId']}'), child: AppTextEditor(args['articleId'])),
    ],
  },
),


// inside AppTextEditor

AdvancedNavigator(
  parent: AdvancedNavigator.of(context),
  paths: {
    '/': (_) => [
      CupertinoPage(key: ValueKey('editor'), child: ViewTextEditor()),
    ],
    '/stats': (_) => [
      CupertinoPage(key: ValueKey('editor'), child: ViewTextEditor()),
      CupertinoPage(key: ValueKey('stats'), child: ViewArticleStats()),
    ],
    '/settings': (_) => [
      CupertinoPage(key: ValueKey('editor'), child: ViewTextEditor()),
      CupertinoPage(key: ValueKey('settings'), child: ViewArticleSettings()),
    ],
  },
),

With this setup the app will support the following navigation requests, both from inside the app through openNamed() or from an external source such as the web broswer url:

  • '/'
  • '/myArticles'
  • '/myArticles/9420ad99c0ec'
  • '/myArticles/9420ad99c0ec/stats'
  • '/myArticles/9420ad99c0ec/settings'

At the same time, navigation requests directed at the child navigator such as openNamed('/stats') will update the global URI as well, in this case to '/myArticles/9420ad99c0ec/stats'.

Nesting is extremely useful, not just for dealing with presistent UI components but also for capsulating components of an app. Given the example above, AppTextEditor can now be entirely separate from the rest of the app. The text editor pages are in a separate hirarchical layer which means all the presentation logic (e.g. BLoCs) can now behave as if there was only one article.

About #

Initially, I only created this package to easily port all of my Flutter projects to the new Navigator 2.0 without having to rewrite the same code over and over again and only spontaneously decided to make it open source. Consequently, there may be a few use cases which this library is not yet properly optimized for. In that case, feel free to create an issue with a feature request.

Issues and PRs are welcome.

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Flutter's Navigator 2.0 as one easy-to-use widget with full page history manipulation operations, simplified pop event delegation and powerful nesting.

Repository (GitHub)
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Documentation

API reference

Uploader

lucas.aschenbach@gmail.com

License

MIT (LICENSE)

Dependencies

flutter

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