didChangeMetrics method

void didChangeMetrics()

Called when the application's dimensions change. For example, when a phone is rotated.

This method exposes notifications from dart:ui.PlatformDispatcher.onMetricsChanged.

This StatefulWidget implements the parts of the State and WidgetsBindingObserver protocols necessary to react when the device is rotated (or otherwise changes dimensions).
link 
class MetricsReactor extends StatefulWidget { const MetricsReactor({ super.key }); @override State<MetricsReactor> createState() => _MetricsReactorState(); } class _MetricsReactorState extends State<MetricsReactor> with WidgetsBindingObserver { late Size _lastSize; @override void initState() { super.initState(); WidgetsBinding.instance.addObserver(this); } @override void didChangeDependencies() { super.didChangeDependencies(); // [View.of] exposes the view from `WidgetsBinding.instance.platformDispatcher.views` // into which this widget is drawn. _lastSize = View.of(context).physicalSize; } @override void dispose() { WidgetsBinding.instance.removeObserver(this); super.dispose(); } @override void didChangeMetrics() { setState(() { _lastSize = View.of(context).physicalSize; }); } @override Widget build(BuildContext context) { return Text('Current size: $_lastSize'); } }

In general, this is unnecessary as the layout system takes care of automatically recomputing the application geometry when the application size changes.

See also:

Implementation

void didChangeMetrics() {}