![]() Now some comments about the StatefulWidget code: The full code you can play with is available in the DartPad. Let’s see the sample code and produced GUI: This class maintains the actual state and it is now who provides the build() method’s implementation. Instead, it implements a createState() method, which creates the initial widget’s state (see below).Īpart from the main widget class, which itself is still “final” (or better said – immutable), you create a class extending State. Unlike StatelessWidgets, StatefulWidget doesn’t override the build() method. You do it by creating a Dart class extending StatefulWidget. When you want your widget to change over time and maintain its state (in most cases you do), you can create a stateful widget. StatelessWidget is simple, works and is just there □ Let’s see something more interesting now – StatefulWidgets. Notice the usage of a Container widget, which is very useful for grouping other widgets. As mentioned before, it overrides the build() method, which simply returns another widget tree. body of our Scaffold is our first own stateless widget – MyFirstWidget.Scaffold also gives us many things “for free”, e.g. It provides us with an appBar and body properties – setting them we’re getting this nice-looking application’s skeleton with entitled app bar and home for our widget. we used another material widget – a Scaffold.There’s a similar widget for Apple-oriented widgets called CupertinoApp, which allows using Cupertino widgets As soon as you use it, you can nest more material widgets from the widgets library. MaterialApp widget gives us material design for our app out of the box. as our main widget, we used MaterialApp and provided it to runApp() method.There are quite a few new things in the source code. You can play with it yourself in the DartPad. Here’s the sample source code and a view it generates: You create it by simply creating a class extending StatelessWidget. The simplest widget you can create is a stateless widget. However, each widget type does it a bit differently. The main purpose of each type of widget is to provide an implementation of a build() method which returns a Widget object. Depending on whether your widget actually manages any state and changes over time, you have two types of base classes to inherit from – StatelessWidget or StatefulWidget. Widget is just a Dart class which extends a proper base class. In Flutter, you can – and will – create your own widgets. After doing this, you can see the selected widget’s properties in the inspector. There’s a very handy feature “Select Widget Mode” which, when enabled, lets you select the widgets directly in your emulator or phone. It opens in a web browser and allows you to see the whole widgets tree in your app: Flutter Inspector (part of Dart DevTools) While in debug mode in Visual Studio Code, you can launch it by clicking the blue magnifier icon: A button for opening Flutter Widgets Inspector from VS Code SOLID also applies here □ Viewing Flutter widgets with Flutter InspectorĪs widgets tree may get big and quite heavily nested, there’s a very useful tool to easily view and explore it. ![]() Flutter widgets – as all reusable pieces of code – should not have too many responsibilities. If you have a few huge widgets without much nesting instead, it means that there’s something wrong with your implementation. However, as I mentioned in the previous post, don’t get discouraged by that □ Actually, having a lot of nested widgets in Flutter is a good practice. Widgets nesting sometimes makes simple Flutter apps having a lot of source code inside a single file. Flutter widgets can have their own properties, like textDirection.widgets can have a child or children – this is widgets nesting and it happens all the time and can be very deep.there are many built-in widgets, like Center and Text.This simple example shows us a few interesting facts: As expected, such a simple Flutter app shows a “Hello Flutter!” text at the center of the screen. In our case, it takes a Center widget, which has one child – a Text widget. The runApp() method takes a Widget as its argument. The most basic Flutter app might look as follows: The framework is said to do it efficiently by measuring what has changed in the widgets tree since the last rendering and re-paints only what’s necessary. In some cases, the state can be static and not change over time – see the section below about Flutter widget types for details.Īs soon as a widget’s state changes, Flutter rebuilds its outlook and in effect re-renders the GUI. Widgets define the user interface by their state. Widget is a reusable piece of code, which describes how your application’s UI looks like. Flutter widgets are directly inspired by this idea. If you ever worked with a web framework like React, you should know the concept of components. Viewing Flutter widgets with Flutter Inspector.
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