import 'package:flutter/material.dart';

// состояние клавиатуры
enum KeyboardVisibilityState { visible, hidden }

// определение функции слушателя
typedef OnKeyboardStateChanged = void Function(KeyboardVisibilityState state);

// stateful виджет для отслеживания изменения видимости клавиатуры
class KeyboardVisibility extends StatefulWidget {
  final Widget child;
  final OnKeyboardStateChanged onKeyboardStateChanged;

  const KeyboardVisibility({
    super.key,
    required this.child,
    required this.onKeyboardStateChanged,
  });

  @override
  State<KeyboardVisibility> createState() => _KeyboardVisibilityState();
}

class _KeyboardVisibilityState extends State<KeyboardVisibility> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeMetrics() {
    super.didChangeMetrics();
    checkState();
  }

  void checkState() {
    final value = WidgetsBinding.instance.platformDispatcher.views.first.viewInsets.bottom;
    switch (value != 0.0) {
      case true:
        widget.onKeyboardStateChanged(KeyboardVisibilityState.visible);
      case false:
        widget.onKeyboardStateChanged(KeyboardVisibilityState.hidden);
    }
  }

  @override
  Widget build(BuildContext context) {
    return widget.child;
  }
}

KeyboardVisibility(
  onKeyboardStateChanged: (state) => _showOrHideBottomAction(state),
  child: Form(...),
)

final GlobalKey _repaintBoundaryKey = GlobalKey();

RepaintBoundary(
  key: _repaintBoundaryKey,
  child: CustomPaint(
    painter: MyPainter(),
    ...
  ),
)

import 'package:image_gallery_saver/image_gallery_saver.dart';

Future<void> exportImage() async {
  try {
    RenderRepaintBoundary boundary = _repaintBoundaryKey.currentContext!.findRenderObject() as RenderRepaintBoundary;
    ui.Image image = await boundary.toImage(pixelRatio: 3.0);
    ByteData? byteData = await image.toByteData(format: ui.ImageByteFormat.png);
    Uint8List pngBytes = byteData!.buffer.asUint8List();

    final directory = await getDownloadsDirectory();
    final imgName = 'myapp-${DateTime.now().microsecondsSinceEpoch}';
    final result = await ImageGallerySaver.saveImage(pngBytes, quality: 100, name: imgName);

    if (result['isSuccess']) {
      ScaffoldMessenger.of(context).showSnackBar(
        SnackBar(content: Text('Изображение экспортировано')),
      );
    }
  } catch (e) {
    // Обработайте ошибку (покажите сообщение пользователю, сохраните отчет о сбое)
  }
}

import 'package:screenshot/screenshot.dart';

final controller = ScreenshotController();
final imgBytes = await controller.captureFromWidget(
  widget, // ваш виджет
  targetSize: const Size(320, 520), // размер изображения
  pixelRatio: 3, // соотношение пикселей
);