In a typical mobile application, when you tap on an editable text field or a widget that requires input from the user, the keyboard pops up, covering part of your screen’s content. This is a normal behavior and can be seen in most modern apps. However, if you want to display some information in a specific way, such as using a single-line header at the top of your screen with no padding, the default resize behavior might not fit your needs.
Understanding the Problem
The issue arises from how Flutter handles keyboard appearance and disappearance. By default, when the keyboard is shown, Flutter resizes all widgets in the tree to accommodate it. This is done using a mechanism called resizeToAvoidBottomPadding. However, this resizing can sometimes lead to unexpected results if you’re not careful with your layout.
The Original Solution: Setting resizeToAvoidBottomPadding to False
In the past, one common solution to prevent this resize was to set resizeToAvoidBottomPadding to false in your Scaffold. This property tells Flutter not to adjust the size of its children when a keyboard is shown. However, it’s worth noting that as of my last update, this approach might have some limitations or side effects in certain situations.
// Old solution Scaffold( resizeToAvoidBottomPadding: false, body: // ... )
Updated Solution: Using resizeToAvoidBottomInset with a Twist
Given that resizeToAvoidBottomPadding is now deprecated, the recommended approach involves setting resizeToAvoidBottomInset to false instead. This property works similarly but considers not just padding (space around content) but the actual inset of widgets from the bottom edge of the screen.
// Updated solution Scaffold( resizeToAvoidBottomInset: false, body: // ... )
This method is more precise than its predecessor and directly addresses the problem without introducing additional complexity. However, as you might expect, this approach has limitations as well. For instance, if your layout requires widgets to move upwards when the keyboard appears to accommodate other UI elements or text fields, setting resizeToAvoidBottomInset to false might not provide the desired effect.
A More Involved Solution: Using a SingleChildScrollView and ConstrainedBox
For more complex layouts where simply disabling resizing doesn’t work as expected, you can consider using a SingleChildScrollView. This widget allows Flutter to automatically scroll your screen up just enough when the keyboard is used. However, it’s essential to manage its scrolling behavior properly.
// A more involved solution
Widget build(BuildContext context) {
return Scaffold(
body: SingleChildScrollView(
physics: const NeverScrollableScrollPhysics(),
child: ConstrainedBox(
constraints: BoxConstraints(
minWidth: MediaQuery.of(context).size.width,
minHeight: MediaQuery.of(context).size.height,
),
child: IntrinsicHeight(
child: Column(
mainAxisSize: MainAxisSize.max,
children: [
// CONTENT HERE
],
),
),
),
),
);
}
This approach forces your column to take up the full screen height, which is then wrapped in a SingleChildScrollView. The NeverScrollableScrollPhysics is used so that users cannot scroll around themselves, ensuring that only scrolling caused by the keyboard’s appearance is handled.
Conclusion
When the keyboard appears and your Flutter widgets resize unexpectedly, you have a few strategies to consider. Setting resizeToAvoidBottomInset to false provides an effective solution in many cases, especially if your layout doesn’t require moving content upwards when the keyboard is shown.
If more control or specific behavior is needed, using a SingleChildScrollView and ensuring appropriate scrolling physics can be quite effective. The key is understanding how Flutter handles keyboard events and choosing the approach that best fits your application’s needs.
