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GetX – Open screens/snackbars/dialogs/bottomSheets without context, manage states and inject dependencies

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Languages: English (this file), Brazilian Portuguese, Spanish,Polish.

About Get 

In addition, the entire development process can be completely automated, both on the server and on the front end with Get CLI.

In addition, to further increase your productivity, we have the extension to VSCode and the extension to Android Studio/Intellij

GetX Community channels:

GetX has a highly active and helpful community. If you have questions, or would like any assistance regarding the use of this framework, please join our community channels, your question will be answered more quickly, and it will be the most suitable place. This repository is exclusive for opening issues, and requesting resources, but feel free to be part of GetX Community.

Installing 

Add Get to your pubspec.yaml file:

dependencies:
  get:

Import get in files that it will be used:

import 'package:get/get.dart';

Counter App with GetX 

The “counter” project created by default on new project on Flutter has over 100 lines (with comments). To show the power of Get, I will demonstrate how to make a “counter” changing the state with each click, switching between pages and sharing the state between screens, all in an organized way, separating the business logic from the view, in ONLY 26 LINES CODE INCLUDING COMMENTS.

void main() => runApp(GetMaterialApp(home: Home()));

class Controller extends GetxController{
  var count = 0.obs;
  increment() => count++;
}

class Home extends StatelessWidget {

  // Instantiate your class using Get.put() to make it available for all "child" routes there.
  final Controller c = Get.put(Controller());

  @override
  Widget build(context) => Scaffold(
      // Use Obx(()=> to update Text() whenever count is changed.
      appBar: AppBar(title: Obx(() => Text("Clicks: ${c.count}"))),

      // Replace the 8 lines Navigator.push by a simple Get.to(). You don't need context
      body: Center(child: RaisedButton(
              child: Text("Go to Other"), onPressed: () => Get.to(Other()))),
      floatingActionButton:
          FloatingActionButton(child: Icon(Icons.add), onPressed: c.increment));
}

class Other extends StatelessWidget {
  // You can ask Get to find a Controller that is being used by another page and redirect you to it.
  final Controller c = Get.find();

  @override
  Widget build(context){
     // Access the updated count variable
     return Scaffold(body: Center(child: Text("${c.count}")));
  }
}

Result:

This is a simple project but it already makes clear how powerful Get is. As your project grows, this difference will become more significant.

Get was designed to work with teams, but it makes the job of an individual developer simple.

Improve your deadlines, deliver everything on time without losing performance. Get is not for everyone, but if you identified with that phrase, Get is for you!

The Three pillars 

State management 

There are currently several state managers for Flutter. However, most of them involve using ChangeNotifier to update widgets and this is a bad and very bad approach to performance of medium or large applications. You can check in the official Flutter documentation that ChangeNotifier should be used with 1 or a maximum of 2 listeners, making it practically unusable for any application medium or large.

Get isn’t better or worse than any other state manager, but that you should analyze these points as well as the points below to choose between using Get in pure form (Vanilla), or using it in conjunction with another state manager.

Definitely, Get is not the enemy of any other state manager, because Get is a microframework, not just a state manager, and can be used either alone or in conjunction with them.

Get has two different state managers: the simple state manager (we’ll call it GetBuilder) and the reactive state manager (who has the package name, GetX)

Reactive State Manager 

Reactive programming can alienate many people because it is said to be complicated. GetX turns reactive programming into something quite simple:

Reactive programming with Get is as easy as using setState.

Let’s imagine that you have a name variable and want that every time you change it, all widgets that use it are automatically changed.

This is your count variable:

var name = 'Jonatas Borges';

To make it observable, you just need to add “.obs” to the end of it:

var name = 'Jonatas Borges'.obs;

And in the UI, when you want to show that value and update the screen whenever tha values changes, simply do this:

Obx(() => Text("${controller.name}"));

That’s all. It’s that simple.

More details about state management 

See an more in-depth explanation of state management here. There you will see more examples and also the difference between the simple stage manager and the reactive state manager

Video explanation about state management 

Amateur Coder did an awesome video about state management! Link: Complete GetX State Management

You will get a good idea of GetX power.

Route management 

If you are going to use routes/snackbars/dialogs/bottomsheets without context, GetX is excellent for you too, just see it:

Add “Get” before your MaterialApp, turning it into GetMaterialApp

GetMaterialApp( // Before: MaterialApp(
  home: MyHome(),
)

Navigate to new screen:


Get.to(NextScreen());

To close snackbars, dialogs, bottomsheets, or anything you would normally close with Navigator.pop(context);

Get.back();

To go to the next screen and no option to go back to the previous screen (for use in SplashScreens, login screens and etc.)

Get.off(NextScreen());

To go to the next screen and cancel all previous routes (useful in shopping carts, polls, and tests)

Get.offAll(NextScreen());

Noticed that you didn’t had to use context to do any of these things? That’s one of the biggest advantages of using Get route management. With this, you can execute all these methods from within your controller class, without worries.

More details about route management 

Get work with named routes and also offer a lower level control over your routes! There is a in-depth documentation here

Video Explanation 

Amateur Coder did an excellent video that cover route management with Get! here is the link: Complete Getx Navigation

Dependency management 

Get has a simple and powerful dependency manager that allows you to retrieve the same class as your Bloc or Controller with just 1 lines of code, no Provider context, no inheritedWidget:

Controller controller = Get.put(Controller()); // Rather Controller controller = Controller();

Instead of instantiating your class within the class you are using, you are instantiating it within the Get instance, which will make it available throughout your App. So you can use your controller (or class Bloc) normally

Tip: Get dependency management is decloupled from other parts of the package, so if for example your app is already using a state manager (any one, it doesn’t matter), you don’t need to rewrite it all, you can use this dependency injection with no problems at all

controller.fetchApi();

Imagine that you have navigated through numerous routes, and you need a data that was left behind in your controller, you would need a state manager combined with the Provider or Get_it, correct? Not with Get. You just need to ask Get to “find” for your controller, you don’t need any additional dependencies:

Controller controller = Get.find();
//Yes, it looks like Magic, Get will find your controller, and will deliver it to you. You can have 1 million controllers instantiated, Get will always give you the right controller.

And then you will be able to recover your controller data that was obtained back there:

Text(controller.textFromApi);

More details about dependency management 

See a more in-depth explanation of dependency management here

How to contribute 

Want to contribute to the project? We will be proud to highlight you as one of our collaborators. Here are some points where you can contribute and make Get (and Flutter) even better.

Any contribution is welcome!

Utils 

Internationalization 

Translations 

Translations are kept as a simple key-value dictionary map. To add custom translations, create a class and extend Translations.

import 'package:get/get.dart';

class Messages extends Translations {
  @override
  Map<String, Map<String, String>> get keys => {
        'en_US': {
          'hello': 'Hello World',
        },
        'de_DE': {
          'hello': 'Hallo Welt',
        }
      };
}

Using translations

Just append .tr to the specified key and it will be translated, using the current value of Get.locale and Get.fallbackLocale.

Text('title'.tr);

Locales 

Pass parameters to GetMaterialApp to define the locale and translations.

return GetMaterialApp(
    translations: Messages(), // your translations
    locale: Locale('en', 'US'), // translations will be displayed in that locale
    fallbackLocale: Locale('en', 'UK'), // specify the fallback locale in case an invalid locale is selected.  
    supportedLocales: <Locale>[Locale('en', 'UK'),  Locale('en', 'US'), Locale('de','DE')] // specify the supported locales
);

Change locale

Call Get.updateLocale(locale) to update the locale. Translations then automatically use the new locale.

var locale = Locale('en', 'US');
Get.updateLocale(locale);

System locale

To read the system locale, you could use window.locale.

import 'dart:ui' as ui;

return GetMaterialApp(
    locale: ui.window.locale,
);

Change Theme 

Please do not use any higher level widget than GetMaterialApp in order to update it. This can trigger duplicate keys. A lot of people are used to the prehistoric approach of creating a “ThemeProvider” widget just to change the theme of your app, and this is definitely NOT necessary with GetX™.

You can create your custom theme and simply add it within Get.changeTheme without any boilerplate for that:

Get.changeTheme(ThemeData.light());

If you want to create something like a button that changes the Theme in onTap, you can combine two GetX™ APIs for that:

Get.changeTheme(Get.isDarkMode? ThemeData.light(): ThemeData.dark());

When .darkmode is activated, it will switch to the light theme, and when the light theme becomes active, it will change to dark theme.

If you want to know in depth how to change the Theme, you can follow this tutorial on Medium which even teaches the persistence of the theme using GetX™:

Other Advanced APIs 

// give the current args from currentScreen
Get.arguments

// give arguments of previous route
Get.previousArguments

// give name of previous route
Get.previousRoute

// give the raw route to access for example, rawRoute.isFirst()
Get.rawRoute

// give access to Rounting API from GetObserver
Get.routing

// check if snackbar is open
Get.isSnackbarOpen

// check if dialog is open
Get.isDialogOpen

// check if bottomsheet is open
Get.isBottomSheetOpen

// remove one route.
Get.removeRoute()

// back repeatedly until the predicate returns true.
Get.until()

// go to next route and remove all the previous routes until the predicate returns true.
Get.offUntil()

// go to next named route and remove all the previous routes until the predicate returns true.
Get.offNamedUntil()

//Check in what platform the app is running
GetPlatform.isAndroid
GetPlatform.isIOS
GetPlatform.isMacOS
GetPlatform.isWindows
GetPlatform.isLinux
GetPlatform.isFuchsia

//Check the device type
GetPlatform.isMobile
GetPlatform.isDesktop
//All platforms are supported independently in web!
//You can tell if you are running inside a browser
//on Windows, iOS, OSX, Android, etc.
GetPlatform.isWeb


// Equivalent to : MediaQuery.of(context).size.height, 
// but immutable.
Get.height
Get.width

// Gives the current context of the Navigator.
Get.context

// Gives the context of the snackbar/dialog/bottomsheet in the foreground, anywhere in your code.
Get.contextOverlay

// Note: the following methods are extensions on context. Since you
// have access to context in any place of your UI, you can use it anywhere in the UI code

// If you need a changeable height/width (like Desktop or browser windows that can be scaled) you will need to use context.
context.width
context.height
 
// Gives you the power to define half the screen, a third of it and so on.
// Useful for responsive applications.
// param dividedBy (double) optional - default: 1
// param reducedBy (double) optional - default: 0
context.heightTransformer()
context.widthTransformer()

/// Similar to MediaQuery.of(context).size
context.mediaQuerySize()

/// Similar to MediaQuery.of(context).padding
context.mediaQueryPadding()

/// Similar to MediaQuery.of(context).viewPadding
context.mediaQueryViewPadding()

/// Similar to MediaQuery.of(context).viewInsets;
context.mediaQueryViewInsets()

/// Similar to MediaQuery.of(context).orientation;
context.orientation()

/// Check if device is on landscape mode
context.isLandscape()

/// Check if device is on portrait mode
context.isPortrait()

/// Similar to MediaQuery.of(context).devicePixelRatio;
context.devicePixelRatio()

/// Similar to MediaQuery.of(context).textScaleFactor;
context.textScaleFactor()

/// Get the shortestSide from screen
context.mediaQueryShortestSide()

/// True if width be larger than 800
context.showNavbar()

/// True if the shortestSide is smaller than 600p
context.isPhone()

/// True if the shortestSide is largest than 600p
context.isSmallTablet()

/// True if the shortestSide is largest than 720p
context.isLargeTablet()

/// True if the current device is Tablet
context.isTablet()

/// Returns a value<T> according to the screen size
/// can give value for:
/// watch: if the shortestSide is smaller than 300
/// mobile: if the shortestSide is smaller than 600
/// tablet: if the shortestSide is smaller than 1200
/// desktop: if width is largest than 1200  
context.responsiveValue<T>()

Optional Global Settings and Manual configurations 

GetMaterialApp configures everything for you, but if you want to configure Get manually.

MaterialApp(
  navigatorKey: Get.key,
  navigatorObservers: [GetObserver()],
);

You will also be able to use your own Middleware within GetObserver, this will not influence anything.

MaterialApp(
  navigatorKey: Get.key,
  navigatorObservers: [
    GetObserver(MiddleWare.observer) // Here
  ],
);

You can create Global Settings for Get. Just add Get.config to your code before pushing any route. Or do it directly in your GetMaterialApp

GetMaterialApp(
  enableLog: true,
  defaultTransition: Transition.fade,
  opaqueRoute: Get.isOpaqueRouteDefault,
  popGesture: Get.isPopGestureEnable,
  transitionDuration: Get.defaultDurationTransition,
  defaultGlobalState: Get.defaultGlobalState,
);

Get.config(
  enableLog = true,
  defaultPopGesture = true,
  defaultTransition = Transitions.cupertino
)

You can optionally redirect all the logging messages from Get. If you want to use your own, favourite logging package, and want to capture the logs there:

GetMaterialApp(
  enableLog: true,
  logWriterCallback: localLogWriter,
);

void localLogWriter(String text, {bool isError = false}) {
  // pass the message to your favourite logging package here
  // please note that even if enableLog: false log messages will be pushed in this callback
  // you get check the flag if you want through GetConfig.isLogEnable
}

Local State Widgets 

These Widgets allows you to manage a single value, and keep the state ephemeral and locally. We have flavours for Reactive and Simple. For instance, you might use them to toggle obscureText in a TextField, maybe create a custom Expandable Panel, or maybe modify the current index in BottomNavigationBar while changing the content of the body in a Scaffold.

ValueBuilder

A simplification of StatefulWidget that works with a .setState callback that takes the updated value.

ValueBuilder<bool>(
  initialValue: false,
  builder: (value, updateFn) => Switch(
    value: value,
    onChanged: updateFn, // same signature! you could use ( newValue ) => updateFn( newValue )
  ),
  // if you need to call something outside the builder method.
  onUpdate: (value) => print("Value updated: $value"),
  onDispose: () => print("Widget unmounted"),   
),

ObxValue

Similar to ValueBuilder, but this is the Reactive version, you pass a Rx instance (remember the magical .obs?) and updates automatically… isn’t it awesome?

ObxValue((data) => Switch(
        value: data.value,
        onChanged: data, // Rx has a _callable_ function! You could use (flag) => data.value = flag,
    ),
    false.obs,
),

Useful tips 

.observables (also known as Rx Types) have a wide variety of internal methods and operators.

Is very common to believe that a property with .obs IS the actual value… but make no mistake! We avoid the Type declaration of the variable, because Dart’s compiler is smart enough, and the code looks cleaner, but:

var message = 'Hello world'.obs;
print( 'Message "$message" has Type ${message.runtimeType}');

Even if message prints the actual String value, the Type is RxString!

So, you can’t do message.substring( 0, 4 ). You have to access the real value inside the observable: The most “used way” is .value, but, did you know that you can also use…

final name = 'GetX'.obs;
// only "updates" the stream, if the value is different from the current one. 
name.value = 'Hey';

// this weird (and kinda cool) assignment, updates the stream no matter what
// it takes nulls, or same value... but rebuilds the observers.
name << 'Hey'; // !

// All Rx properties are "callable" and returns the new value.
// but this approach does not accepts `null`, the UI will not rebuild.
name('Hello');

// is like a getter, prints 'Hello'.
name() ;

/// numbers:

final count = 0.obs; 

// you can just most basic operators acts on the property!
count + 1;
 
// Watch out! this is only valid if `count` is not final, but var
count += 1;

// You can also compare against values:
count > 2;

/// booleans:

final flag = false.obs;

// switches the value between true/false
flag.toggle();


/// all types:

// Sets the `value` to null.
flag.nil();

// All toString(), toJson() operations are passed down to the `value`
print( count ); // calls `toString()` inside  for RxInt

final abc = [0,1,2].obs;
// Converts the value to a json Array, prints RxList
// Json is supported by all Rx types!
print('json: ${jsonEncode(abc)}, type: ${abc.runtimeType}'); 

// RxMap, RxList and RxSet are special Rx types, that extends their native types.
// but you can work with a List as a regular list, although is reactive!
abc.add(12); // pushes 12 to the list, and UPDATES the stream.
abc[3]; // like Lists, reads the index 3.


// equality works with the Rx and the value, but hashCode is always taken from the value
final number = 12.obs;
print( number == 12 ); // prints > true

/// Custom Rx Models:

// toJson(), toString() are deferred to the child, so you can implement override on them, and print() the observable directly. 

class User {
    String name, last;
    int age;
    User({this.name, this.last, this.age});
    
    @override
    String toString() => '$name $last, $age years old';
}

final user = User(name: 'John', last: 'Doe', age: 33).obs;

// `user` is "reactive", but the properties inside ARE NOT!
// So, if we change some variable inside of it...
user.value.name = 'Roi';
// The widget will not rebuild!,
// `Rx` don't have any clue when you change something inside user.
// So, for custom classes, we need to manually "notify" the change.
user.refresh();

// or we can use the `update()` method!
user.update((value){
  value.name='Roi';
});

print( user );

// this also works.
user << user.value;

GetView

I love this Widget, is so simple, yet, so useful!

Is a const Stateless Widget that has a getter controller for a registered Controller, that’s all.

 class AwesomeController extends GetxController {
   final String title = 'My Awesome View';
 }
  
  // ALWAYS remember to pass the `Type` you used to register your controller!
 class AwesomeView extends GetView<AwesomeController> {
   @override
   Widget build(BuildContext context) {
     return Container(
       padding: EdgeInsets.all(20),
       child: Text( controller.title ), // just call `controller.something`
     );
   }
 }

GetWidget

Most people have no idea about this Widget, or totally confuse the usage of it. The use case is very rare, but very specific: It caches a Controller. Because of the cache, can’t be a const Stateless.

So, when do you need to “cache” a Controller?

If you use, another “not so common” feature of GetX: Get.create().

Get.create(()=>Controller()) will generate a new Controller each time you call Get.find<Controller>(),

That’s where GetWidget shines… as you can use it, for example, to keep a list of Todo items. So, if the widget gets “rebuilt”, it will keep the same controller instance.

GetxService

This class is like a GetxController, it shares the same lifecycle ( onInit(), onReady(), onClose()). But has no “logic” inside of it. It just notifies GetX Dependency Injection system, that this subclass can not be removed from memory.

So is super useful to keep your “Services” always reachable and active with Get.find(). Like: ApiService, StorageService, CacheService.

Future<void> main() async {
  await initServices(); /// AWAIT SERVICES INITIALIZATION.
  runApp(SomeApp());
}

/// Is a smart move to make your Services intiialize before you run the Flutter app.
/// as you can control the execution flow (maybe you need to load some Theme configuration, 
/// apiKey, language defined by the User... so load SettingService before running ApiService.
/// so GetMaterialApp() doesnt have to rebuild, and takes the values directly.    
void initServices() async {
  print('starting services ...');
  /// Here is where you put get_storage, hive, shared_pref initialization.
  /// or moor connection, or whatever that's async.
  await Get.putAsync(() => DbService().init());
  await Get.putAsync(SettingsService()).init();
  print('All services started...');
}

class DbService extends GetxService {
  Future<DbService> init() async {
    print('$runtimeType delays 2 sec');
    await 2.delay();
    print('$runtimeType ready!');
    return this;
  }
}

class SettingsService extends GetxService {
  void init() async {
    print('$runtimeType delays 1 sec');
    await 1.delay();
    print('$runtimeType ready!');
  }
}

The only way to actually delete a GetxService, is with Get.reset() which is like a “Hot Reboot” of your app. So remember, if you need absolute persistance of a class instance during the lifetime of your app, use GetxService.

Video explanation of Other GetX Features 

Amateur Coder did an awesome video about utils, storage, bindings and other features! Link: GetX Other Features

Breaking changes from 2.0 

1- Rx types:

BeforeAfter
StringXRxString
IntXRxInt
MapXRxMap
ListXRxList
NumXRxNum
DoubleXRxDouble

RxController and GetBuilder now have merged, you no longer need to memorize which controller you want to use, just use GetxController, it will work for simple state management and for reactive as well.

2- NamedRoutes Before:

GetMaterialApp(
  namedRoutes: {
    '/': GetRoute(page: Home()),
  }
)

Now:

GetMaterialApp(
  getPages: [
    GetPage(name: '/', page: () => Home()),
  ]
)

Why this change? Often, it may be necessary to decide which page will be displayed from a parameter, or a login token, the previous approach was inflexible, as it did not allow this. Inserting the page into a function has significantly reduced the RAM consumption, since the routes will not be allocated in memory since the app was started, and it also allowed to do this type of approach:


GetStorage box = GetStorage();

GetMaterialApp(
  getPages: [
    GetPage(name: '/', page:(){  
      return box.hasData('token') ? Home() : Login();
    })
  ]
)

Why Getx? 

1- Many times after a Flutter update, many of your packages will break. Sometimes compilation errors happen, errors often appear that there are still no answers about, and the developer needs to know where the error came from, track the error, only then try to open an issue in the corresponding repository, and see its problem solved. Get centralizes the main resources for development (State, dependency and route management), allowing you to add a single package to your pubspec, and start working. After a Flutter update, the only thing you need to do is update the Get dependency, and get to work. Get also resolves compatibility issues. How many times a version of a package is not compatible with the version of another, because one uses a dependency in one version, and the other in another version? This is also not a concern using Get, as everything is in the same package and is fully compatible.

2- Flutter is easy, Flutter is incredible, but Flutter still has some boilerplate that may be unwanted for most developers, such as Navigator.of(context).push (context, builder [...]. Get simplifies development. Instead of writing 8 lines of code to just call a route, you can just do it: Get.to(Home()) and you’re done, you’ll go to the next page. Dynamic web urls are a really painful thing to do with Flutter currently, and that with GetX is stupidly simple. Managing states in Flutter, and managing dependencies is also something that generates a lot of discussion, as there are hundreds of patterns in the pub. But there is nothing as easy as adding a “.obs” at the end of your variable, and place your widget inside an Obx, and that’s it, all updates to that variable will be automatically updated on the screen.

3- Ease without worrying about performance. Flutter’s performance is already amazing, but imagine that you use a state manager, and a locator to distribute your blocs/stores/controllers/ etc. classes. You will have to manually call the exclusion of that dependency when you don’t need it. But have you ever thought of simply using your controller, and when it was no longer being used by anyone, it would simply be deleted from memory? That’s what GetX does. With SmartManagement, everything that is not being used is deleted from memory, and you shouldn’t have to worry about anything but programming. You will be assured that you are consuming the minimum necessary resources, without even having created a logic for this.

4- Actual decoupling. You may have heard the concept “separate the view from the business logic”. This is not a peculiarity of BLoC, MVC, MVVM, and any other standard on the market has this concept. However, this concept can often be mitigated in Flutter due to the use of context. If you need context to find an InheritedWidget, you need it in the view, or pass the context by parameter. I particularly find this solution very ugly, and to work in teams we will always have a dependence on View’s business logic. Getx is unorthodox with the standard approach, and while it does not completely ban the use of StatefulWidgets, InitState, etc., it always has a similar approach that can be cleaner. Controllers have life cycles, and when you need to make an APIREST request for example, you don’t depend on anything in the view. You can use onInit to initiate the http call, and when the data arrives, the variables will be populated. As GetX is fully reactive (really, and works under streams), once the items are filled, all widgets that use that variable will be automatically updated in the view. This allows people with UI expertise to work only with widgets, and not have to send anything to business logic other than user events (like clicking a button), while people working with business logic will be free to create and test the business logic separately.

This library will always be updated and implementing new features. Feel free to offer PRs and contribute to them.

How to contribute

Want to contribute to the project? We will be proud to highlight you as one of our collaborators. Here are some points where you can contribute and make Get (and Flutter) even better.

Any contribution is welcome!

Download GetX opensource code on GitHub

https://github.com/jonataslaw/getx

Check out the GetX implementation details on Pub

https://pub.dev/packages/get

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