How to Prevent Flutter Text Field Input from Disappearing on Focus Loss

Описание: Learn how to resolve the issue of lost input text in Flutter when switching focus between text fields in your login screen. Simple steps included!
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This video is based on the question https://stackoverflow.com/q/66496402/ asked by the user 'Yusof Antar' ( https://stackoverflow.com/u/14865120/ ) and on the answer https://stackoverflow.com/a/66497389/ provided by the user 'Ahsan Zulfiqar' ( https://stackoverflow.com/u/12445666/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Prevent Flutter Text Field Input from Disappearing on Focus Loss

Creating a login page in Flutter can be straightforward, but sometimes unexpected issues arise, like losing text input when switching between fields. If you have experienced the frustrating problem where everything you've typed in a text field disappears as soon as you switch focus, don't worry! This guide will identify the issue and provide a simple solution to keep your user input intact.

The Problem

When building a login screen with multiple text input fields, you might notice that the text disappears when you navigate between fields. For instance, if you have text fields for a username and a password, switching between these two fields may cause the inputted text to be lost.

Here’s the structure of a typical login screen you might have:

A text field for username

A text field for password

When you attempt to transition from the username field to the password field, or vice versa, the text disappears.

Example Code

In the code snippet below, we use TextEditingController for managing both the username and password fields:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

Fortunately, the fix for this issue is quite simple. The application of TextEditingController needs adjustment to stay functional during field focus changes.

Move the Controllers

The main solution here is to ensure that the TextEditingController variables are declared outside of the build method within your widget. To implement this fix, follow these steps:

Declare Controllers as Class Members:
Move the declaration of your TextEditingController instances outside the build() method, which allows them to retain their state regardless of widget rebuilds.

[[See Video to Reveal this Text or Code Snippet]]

Retain State:
By defining _username and _password as class properties, you're allowing the app to maintain their state even when the widget gets rebuilt during navigation between fields.

Use the Controllers in your Widget:
Ensure that the text fields in your widget use these controller instances properly, as seen in your original setup, so that the text input from the user persists.

Example of Revised Code

Here’s how your revised login screen code might look:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By implementing these changes in your Flutter app, you can effectively solve the problem of lost text input in your text fields when navigation occurs. Moving the TextEditingController instances outside the build method ensures that they persist beyond widget rebuilds, leading to a smoother user experience.

Now, your login screen will function correctly, and users can switch between the input fields without losing any entered text.

Feel free to implement these changes and enjoy a hassle-free login experience in your Flutter apps!