11.1. Working with forms in Flutter: Creating a basic form

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Developing apps with Flutter and Dart is a challenging and rewarding task. Understanding how to work with forms is a crucial part of application development. In this chapter, we are going to discuss how to create a basic form in Flutter.

First, we need to understand what a form is. In simple terms, a form is a way to collect information from the user. In Flutter, this is done using the 'Form' class. This class is a widget that groups together multiple form field widgets and allows validation of their values.

To start creating a form, we need to import Flutter's material design library. This can be done by adding 'import 'package:flutter/material.dart';' at the beginning of our Dart file.

After importing the material library, we can start creating our basic form. First, we create a new stateful widget called 'MyForm'. In Flutter, a stateful widget is a widget that can change over time. This is perfect for a form, as the form field values can change based on user input.

Next, inside the 'MyFormState' class, we declare a variable for our 'GlobalKey'. The 'GlobalKey' is used to identify our form and allows us to validate and save the form field values.

After that, we can start building the structure of our form. We use the 'Form' widget and pass our 'GlobalKey' to the 'key' argument. Inside the 'Form' widget, we can start adding our form fields.

For a basic form, let's start with a single text field. This can be done using the 'TextFormField' widget. This widget creates a text field that can be validated and saved. We can add a 'decoration' argument to add labels, text hints and icons to our text field.

To validate the value of our text field, we can add a 'validator' argument to our 'TextFormField' widget. The 'validator' argument takes a function that is called when the form is validated. If the function returns a string, that string is used as the error message. If the function returns null, it means that the text field value is valid.

To save the value of the text field, we can add an 'onSaved' argument to our 'TextFormField' widget. The 'onSaved' argument takes a function that is called when the form is saved. In this function, we can set the value of our text field to the variable we want.

Finally, to submit our form, we can add a button to our form. This can be done using the 'RaisedButton' widget. The 'RaisedButton' widget creates a button that, when pressed, can call a function. In this function, we can validate and save our form using the 'validate' and 'save' methods of our 'GlobalKey'.

In summary, creating a basic form in Flutter involves creating a new stateful widget, declaring a 'GlobalKey', building the structure of the form using the 'Form' widget, adding form fields using the 'TextFormField' widget, validating and saving form field values, and adding a button to submit the form.

Although this is a basic form, Flutter allows a great deal of flexibility in creating forms. We can add as many form fields as we want, each with its own validation and saving rules. In addition, we can style our form and its fields to suit the design of our application.

Understanding how to work with forms in Flutter is an essential skill for any app developer. I hope this guide has given you a solid introduction to creating a basic form in Flutter. With practice and experience, you will be able to create more complex and customized forms for your applications.

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