This implementation seems dynamic as it has 3 pages and on making changes on any of these pages the changes are reflected on the HomePage as well. Navigating to ModifyPage and when we return back setState is called to update the UI.Navigating to AddPage and whenever we return back to HomePage setState is invoked.Declare the list as a global variable so that its lifecycle is not bounded to the widget lifecycle and can be accessed from anywhere.This implementation also has some drawbacks which we will look into after the implementation: To resolve this issue in a straightforward manner what we can do is declare our List as a global variable and access it on various other screens. Lifting the State Up using Global Variables □Īs we just saw our list was bound to the lifecycle of the widget. This type of state that spans over two pages is called App State. While in most real-world applications, we persist the data along the screens to provide you with various functionalities, like modifying, deleting, adding, etc. It only has one page and can not persist/hold data across pages. While this code is able to add and show items, it is not much dynamic. This type of State is called Ephemeral State which is bound to a single page. Here, we simply display the contents of the list in a ListView.This is because as soon as we move from this page the to-do list will be disposed of. Here, the thing to note is that we can not redirect the user to another page to add an item. Inside the onPressed of FloatingActionButton, we add another item to the to-do list and call setState to update the current State.Now if we want to use this list out of this page, we can not use it, as it is bound to the lifecycle of the widgets. Please note that the Stateful Widget contains the declaration of the list, now it is a private state to this Stateful Widget. Firstly, we internally create a List to store our data.Let’s look at our traditional implementation first. You can read more about State in my post on State Management in Flutter. There are other packages that provide simple and effective State Management like GetX, BLoC, RiverPod, Provider, etc. The traditional solution to State Management in Flutter is setState however, it comes with some drawbacks like deep coupling, expensive rebuilds, etc. It is the responsibility of the widget implementer to ensure that the State is promptly notified when such state changes, using tState. State is information that can be read synchronously when the widget is built and might change during the lifetime of the widget. However, to use minimal resources, there’s a complete section of packages provided to achieve State Management in Flutter. Flutter is very efficient and can handle multiple state updates at a given time. To achieve dynamic pages and apps we rebuild State again and again as needed. The State remains constant however we in today’s world use dynamic apps. State in basic terms is the description of the app’s current instance. Ways to Consume ChangeNotifier in Flutter □īefore discussing the need for ChangeNotifier we need to have a basic understanding of State in Flutter.Lifting the State Up using Global Variables □.Import 'package:firebase_core/firebase_core. Import 'package:firebase_auth/firebase_auth.dart' Import 'package:cab_rider/widgets/TaxiButton.dart' Tried calling: showSnackBar(Instance of 'SnackBar')Īnd this is my code: import 'package:cab_rider/screens/loginpage.dart' The method 'showSnackBar' was called on null. The following NoSuchMethodError was thrown while handling a gesture: When i try to run this, i got this issue: = Exception caught by gesture = I'm trying to use the new way to show a SnackBar with ScaffoldMessenger instead of Scaffold.
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