In flutter_slidable, the SlidableAction class is used to define custom actions for the Slidable widget. It allows you to create your own custom slide actions to be used within a Slidable.

1. pubspec.yaml

dependencies:
  flutter:
    sdk: flutter
  flutter_slidable: ^0.6.0

2. screen

import 'package:flutter/material.dart';
import 'package:flutter_slidable/flutter_slidable.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  final List<String> items = List.generate(20, (index) => 'Item ${index + 1}');

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Slidable Action Example'),
        ),
        body: ListView.builder(
          itemCount: items.length,
          itemBuilder: (context, index) {
            return Slidable(
              actionPane: SlidableDrawerActionPane(),
              actionExtentRatio: 0.25,
              child: ListTile(
                title: Text(items[index]),
              ),
              actions: [
                SlidableAction(
                  onPressed: (context) {
                    // Handle custom action
                    print('Custom action on item: ${items[index]}');
                  },
                  backgroundColor: Colors.green,
                  foregroundColor: Colors.white,
                  icon: Icons.check,
                  label: 'Complete',
                ),
              ],
              secondaryActions: [
                IconSlideAction(
                  caption: 'Delete',
                  color: Colors.red,
                  icon: Icons.delete,
                  onTap: () {
                    // Handle delete action
                    print('Deleted item: ${items[index]}');
                  },
                ),
              ],
            );
          },
        ),
      ),
    );
  }
}

In this example:

The Slidable widget wraps each ListTile in the ListView.builder.
Inside Slidable, there's a custom action defined using SlidableAction. This action has a green background, a white icon, and a label of "Complete". When triggered, it prints a message to the console.
Additionally, there's a secondary action using IconSlideAction to showcase a default slide action.