How to Build a Custom Flutter Widget from Scratch

Are you tired of using the same old widgets in your Flutter app? Do you want to add some customized functionality to your app? Then, building your own custom widget is the way to go!

In this tutorial, we'll be going through the step-by-step process of building a custom Flutter widget from scratch. We'll cover everything from creating the widget class to adding it to our app.

So, let's dive in!

Requirements

Before we get started, let's set up our development environment. In order to follow along with this tutorial, you'll need to have the following installed:

• Flutter SDK
• Android Studio or any other IDE
• Basic knowledge of Dart

If you don't already have Flutter installed, you can download it from the official Flutter website.

Creating the Widget Class

The first step in building our custom Flutter widget is to create a new widget class. In Flutter, every widget is a class, and our custom widget will be no different.

To create a new widget class, we'll start by creating a new Dart file in our project directory. Let's call it custom_widget.dart. Then, we'll create a new class within this file called CustomWidget.

import 'package:flutter/material.dart';

class CustomWidget extends StatelessWidget {

}

As you can see, we've imported the material.dart library which contains all the widgets and utilities we'll need for our app.

Next, we'll add some properties to our CustomWidget class. For this tutorial, we'll be creating a widget that displays a custom text message, so we'll add a property called text to our class.

import 'package:flutter/material.dart';

class CustomWidget extends StatelessWidget {
  final String text;

  CustomWidget({@required this.text});

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Text(
        text,
        style: TextStyle(fontSize: 24.0),
      ),
    );
  }
}

In the code above, we've added a required string property called text to our class. We've also added a constructor for our class that takes in a required text parameter.

Finally, we've overridden the build method of the StatelessWidget class to return a Container widget that displays our custom text message.

Adding the Widget to our App

Now that we've created our custom widget, let's add it to our app. To do this, we'll create a new Scaffold widget in our main.dart file and add our custom widget to it.

import 'package:flutter/material.dart';
import 'custom_widget.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Custom Widget Demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Custom Widget Demo'),
        ),
        body: Center(
          child: CustomWidget(text: 'Hello World!'),
        ),
      ),
    );
  }
}

In the code above, we've imported our CustomWidget class and added it to the body of our Scaffold widget. We've also added an appBar to our Scaffold to give our app a title.

If you run your app now, you should see your custom widget being displayed in the center of the screen with the text 'Hello World!'.

Customizing the Widget

Now that we know how to create and add our custom widget to our app, let's explore some ways to customize it further.

Adding Custom Properties

One way to customize our custom widget is to add more properties to it. For example, we might want to change the font color or size of our text message.

Let's add a new property called color to our CustomWidget class that allows us to change the font color of our text.

import 'package:flutter/material.dart';

class CustomWidget extends StatelessWidget {
  final String text;
  final Color color;

  CustomWidget({@required this.text, this.color});

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Text(
        text,
        style: TextStyle(fontSize: 24.0, color: color),
      ),
    );
  }
}

We've added a new optional property called color to our class, and we've updated our build method to use this property to change the font color of our text.

Next, let's add our custom widget to our app again and use the new color property to change the font color of our text.

import 'package:flutter/material.dart';
import 'custom_widget.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Custom Widget Demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Custom Widget Demo'),
        ),
        body: Center(
          child: CustomWidget(
            text: 'Hello World!',
            color: Colors.blue,
          ),
        ),
      ),
    );
  }
}

In the code above, we've added a new color property to our custom widget and used it to change the font color of our text to blue.

If you run your app now, you should see the font color of your text change to blue.

Adding Custom Functionality

Another way to customize our custom widget is to add custom functionality to it. For example, we might want to add a button to our widget that performs a custom action when pressed.

Let's add a new method called onPressed to our CustomWidget class that performs a custom action when called.

import 'package:flutter/material.dart';

class CustomWidget extends StatelessWidget {
  final String text;
  final Color color;
  final VoidCallback onPressed;

  CustomWidget({@required this.text, this.color, this.onPressed});

  @override
  Widget build(BuildContext context) {
    return Container(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Text(
            text,
            style: TextStyle(fontSize: 24.0, color: color),
          ),
          RaisedButton(
            onPressed: onPressed,
            child: Text('Press me!'),
          ),
        ],
      ),
    );
  }
}

We've added a new optional property called onPressed to our class, and we've updated our build method to use this property to add a RaisedButton widget to our custom widget. When this button is pressed, it will call the onPressed method we defined.

Next, let's add our custom widget to our app again and use the new onPressed property to perform a custom action.

import 'package:flutter/material.dart';
import 'custom_widget.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Custom Widget Demo',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Custom Widget Demo'),
        ),
        body: Center(
          child: CustomWidget(
            text: 'Hello World!',
            color: Colors.blue,
            onPressed: () {
              print('Button pressed!');
            },
          ),
        ),
      ),
    );
  }
}

In the code above, we've added a new onPressed property to our custom widget and used it to print a message to the console when the button is pressed.

If you run your app now and press the button, you should see a message printed to the console.

Conclusion

And that's it! In this tutorial, we've covered everything you need to know to create your own custom Flutter widget from scratch. We've covered creating the widget class, adding it to our app, and customizing it further by adding properties and functionality.

Creating your own custom widget can add significant value to your Flutter app, allowing you to create unique and customized functionality that adds to the user experience.

So, what are you waiting for? Get started building your own custom Flutter widget today!

Editor Recommended Sites