Dark Mode-aware asset images in Flutter

assets.dart

/// lib/utilities/assets.dart

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

/// Usage:
///
/// The image file is located at lib/assets/images/path/to/image.png.
///
/// 1. Image has no dark mode variant.
/// 
/// Assets.image('path/to/image.png');
///
/// 2. Image has a dark mode variant.
/// 
/// Dark mode variant should be placed at lib/assets/images/dark_mode/path/to/image.png.
/// 
/// Assets.image('path/to/image.png', isDarkModeAware: true);
///
abstract class Assets {
  static AssetImage image(String imagePath, {bool isDarkModeAware}) {
    final isDarkMode = isDarkModeAware &&
        SchedulerBinding.instance.window.platformBrightness == Brightness.dark;

    return isDarkMode
        ? AssetImage('$_imagesFolder/dark_mode/$imagePath')
        : AssetImage('$_imagesFolder/$imagePath');
  }

  static const _imagesFolder = 'lib/assets/images';
}

This workaround no longer works after the merge of flutter/flutter@cb5b5c34. You can see a short discussion here: flutter/flutter#121474.

As far as I know, you'll have to manually add every variant to pubspec.yaml or use a different naming convention (e.g.: suppose you have mountain.png as a light theme image, then you'll need a mountain-dark.png or mountain_dark.png (or whatever you like) for both images to be detected by Flutter properly.