TextFormField in Flutter - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a TextFormField in Flutter?

A TextFormField is a widget that allows users to enter and edit text in a form. It integrates with form validation and saving mechanisms.

beginner

How do you validate user input in a TextFormField?

You provide a validator function that returns an error message string if the input is invalid, or null if it is valid.

beginner

What property do you use to save the input value from a TextFormField?

Use the onSaved property, which takes a function to save the input value when the form is saved.

intermediate

How can you control the text inside a TextFormField programmatically?

By using a TextEditingController assigned to the controller property of the TextFormField.

intermediate

Why should you wrap TextFormField widgets inside a Form widget?

Wrapping inside a Form allows collective validation and saving of multiple fields together using a GlobalKey<FormState>.

Which property of TextFormField is used to check if the input is valid?

A validator

B onChanged

C controller

D onSaved

The validator property is a function that checks the input and returns an error message if invalid.

What does the onSaved callback do in a TextFormField?

A It validates the input

B It saves the input value when the form is saved

C It clears the input field

D It controls the keyboard type

onSaved is called when the form is saved to store the input value.

Which widget should wrap TextFormField widgets to manage form state?

A Scaffold

B Container

C Form

D Column

The Form widget manages the state of multiple TextFormField widgets.

How do you programmatically change the text inside a TextFormField?

A Use a <code>TextEditingController</code>

B Use the <code>onChanged</code> callback

C Use the <code>validator</code> function

D Use the <code>onSaved</code> callback

A TextEditingController lets you read and change the text programmatically.

What happens if the validator function returns a non-null string?

A The form input is considered valid

B The keyboard is dismissed

C The input field is cleared

D The form input is considered invalid and shows the error message

Returning a string from validator means the input is invalid and displays that string as an error.

Explain how to use TextFormField inside a form to collect and validate user input.

Think about how you group fields and check their values before saving.

Describe how TextEditingController works with TextFormField and why it might be useful.

Consider when you want to change or read the text from code, not just user typing.