📐 Flutter ReadyLayoutMixin — Execute Code After First Layout

Sometimes in Flutter, you need to perform certain actions only after the widget has been fully built and laid out — for example, to:

  • Start async tasks right after the UI is ready.
  • Get the size of a widget (like its height or width).
  • Check layout info, like where a widget is placed.
  • Start animations that need to know the size of something.
  • Move or control scroll position after layout.
  • Automatically scroll to a widget or list item.
  • Update state only after the layout is done.
  • Figure out how much space a widget has.
  • Use low-level tools to get widget boundaries.
  • Set up services or dependencies that depend on layout.
  • Begin custom drawing once everything is on screen.
  • Send tracking info once layout is finished.

Make sure a widget is actually visible on the screen.

This is where ReadyLayoutMixin comes in handy. It ensures your code runs exactly once after the first layout is complete.

✅ With ReadyLayoutMixin

Use this approach to simplify post-layout logic without having to manage frame callbacks manually.

Example

class SetStateExample extends StatefulWidget {
 @override
 State<SetStateExample> createState() => _SetStateExampleState();
}

class _SetStateExampleState extends State<SetStateExample>
   with ReadyLayoutMixin<SetStateExample> {
 String label = 'Before layout';

 @override
 void onViewReady(BuildContext context) {
   setState(() {
     label = 'Layout is ready!';
   });
 }

 @override
 Widget build(BuildContext context) => Text(label);
}

❌ Without ReadyLayoutMixin

If you're not using the mixin, you'll need to manually schedule a callback using WidgetsBinding.instance.addPostFrameCallback.

Example

class SetStateExample extends StatefulWidget {
 @override
 State<SetStateExample> createState() => _SetStateExampleState();
}

class _SetStateExample extends State<SetStateExample> {
 String label = 'Before layout';

 @override
 void initState() {
   super.initState();
   // ❌ This will throw an error if it triggers a rebuild too early
   setState(() {
     label = 'Trying to update too soon!';
   });
 }

 @override
 Widget build(BuildContext context) => Text(label);
}

✅ With ReadyLayoutMixin

Use this approach to simplify post-layout logic without having to manage frame callbacks manually.

Example

class AsyncExample extends StatefulWidget {
 @override
 State<AsyncExample> createState() => _AsyncExampleState();
}

class _AsyncExampleState extends State<AsyncExample>
   with ReadyLayoutMixin<AsyncExample> {
 String label = 'Loading...';

 @override
 Future<void> onViewReady(BuildContext context) async {
   // Do your async logic here
   await Future.delayed(Duration(seconds: 2));
   setState(() {
     label = 'Data loaded after layout!';
   });
 }

 @override
 Widget build(BuildContext context) => Text(label);
}

❌ Without ReadyLayoutMixin

If you're not using the mixin, you'll need to manually schedule a callback using WidgetsBinding.instance.addPostFrameCallback.

Example

class AsyncExample extends StatefulWidget {
 @override
 State<AsyncExample> createState() => _AsyncExampleState();
}

class _AsyncExampleState extends State<AsyncExample> {
 String label = 'Loading...';

 @override
 Future<void> initState() async{
   super.initState();
   // ❌ This will throw an error on Asynchronous operation.
   await _doAsyncWork();
 }

 Future<void> _doAsyncWork() async {
   await Future.delayed(Duration(seconds: 2));
   if (mounted) {
     setState(() {
       label = 'Data loaded after layout!';
     });
   }
 }

 @override
 Widget build(BuildContext context) => Text(label);
}

🧠 Summary

Feature With ReadyLayoutMixin Without Mixin (Manual)
Simplicity ✅ Clean, one method ❌ Requires boilerplate
Automatic frame hook ✅ Built-in after-layout logic ❌ Manual post-frame logic needed
Reusability ✅ Easy to mix into many widgets ❌ Code duplication likely

Use ReadyLayoutMixin for a cleaner, reusable, and declarative way to handle first-layout-dependent logic in your Flutter widgets.

Libraries

flutter_ready_layout