Flutter: How to open Drawer programmatically

Null safe code

• Using GlobalKey:

  final GlobalKey<ScaffoldState> _key = GlobalKey(); // Create a key
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      key: _key, // Assign the key to Scaffold.
      drawer: Drawer(),
      floatingActionButton: FloatingActionButton(
        onPressed: () => _key.currentState!.openDrawer(), // <-- Opens drawer
      ),
    );
  }
  

• Using Builder:

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawer: Drawer(),
      floatingActionButton: Builder(builder: (context) {
        return FloatingActionButton(
          onPressed: () => Scaffold.of(context).openDrawer(), // <-- Opens drawer.
        );
      }),
    );
  }
  

If you want to disable opening the Drawer using a drag gesture, you can set

Scaffold(
  drawerEnableOpenDragGesture: false
  // above code ...
)