I want to know the definition of sealed class in Dart

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Flutter: inherit from abstract stateless widget

I have a class that has to take a custom widget. This one can have two different implementations, so I would like to have an abstract class as interface and create two...

How can I get an extension method to change the original object in Dart?

I have <code>bounds</code>. bounds should be extended with new LatLng. <pre><code>var bounds = LatLngBounds(); for (var latlng in _list) bounds.extend(latlng); </c...

How custom json data can be generated in Dart?

I want to generate custom json from this Model: <pre><code>class Book { List&lt;Route&gt; routes; double distance; int rateId; List&lt;int&gt; optionsIds;...

How to create new widget with extending custom widget in flutter?

In the flutter, I have a very complex widget and its working fine. but for the different part of the app, I want to slightly modify the widget, To achieve tha...

Passing a value (age) from a widget to another

Through textfield inputs, age of user is obtained with the following code (truncated for simplicity): <pre><code>onChanged: (valueYear) {...

Flutter : App Build Failed, ProcessException - gradlew.bat exited abnormally:

I have upgraded flutter to Flutter version 1.2.1. After upgrading when I try to build my application, the following error occurs. Cannot find a solution to this yet. A...

Default values of an optional parameter must be constant flutter / dart

I'm trying to organize some Site class data in an Event class, but I'm getting a "The default value of an optional parameter must be constant" and I've been struggling...

Flutter &amp; Dart, Constructor before the properties

I was watching a course and the instructor always write the constructor first, then the properties, in java, c# and other OOP languages the properties are written firs...

Why does the identityHashCode function not work for the built-in type int in Dart?

The documentation of the identityHashCode says: <img src="https://i.stack.imgur.com/G19tU.png" alt="documentation" /> And it indeed works for my custom type 'In...

How can I access global data from another class in Flutter?

I have a simple class like; <pre><code>import 'dart:io'; class IDCardClass { File frontImageFile; File backImageFile; } </code></pre> From <code>front_tes...

flutter text color not changing by class

I am new to flutter. I have created class for Textstyle. But its color is not changed. I have created two classes, one for color variable and other for textstyle. but...

constructor doesnt work properly on flutter

I have create a class called Size <ul> <li>Class name: Size</li> </ul> enter code <pre><code>import 'package:flutter/material.dart'; import 'package:firstap...

Passing data from another class to anothers class onPressed Flutter

I'm trying to pass a data from class A to another class B. Class B would accept it and pass the data to Screen C through onPressed(in class B). Below is how I p...

Flutter: Optional method implementation in child class

I have abstract class . Inside A class I have for example 3 methods: <pre><code>abstract class A { @protected void method1() @protected void method2() @prot...