Flutter CameraPreview in ClipRRect example

main.dart

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

void main() => runApp(const CameraApp());

class CameraApp extends StatefulWidget {
  const CameraApp({Key? key}) : super(key: key);

  @override
  _CameraAppState createState() => _CameraAppState();
}

class _CameraAppState extends State<CameraApp> {
  List<CameraDescription>? _cameras;
  CameraController? _controller;
  int? _index;
  var _isSwitching = false;

  @override
  void initState() {
    super.initState();
    availableCameras().then((cameras) {
      if (!mounted) return;
      setState(() => _cameras = cameras);
    });
  }

  @override
  void dispose() {
    _controller?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final cameras = _cameras;
    final controller = _controller;

    return MaterialApp(
      home: Scaffold(
        body: Column(
          children: [
            SafeArea(
              child: Padding(
                padding: const EdgeInsets.all(8.0),
                child: AspectRatio(
                  aspectRatio: 1,
                  child: LayoutBuilder(
                    builder: (_, constraints) {
                      final width = constraints.maxWidth;
                      assert(width.isFinite);

                      return ClipRRect(
                        borderRadius: BorderRadius.circular(width),
                        child: OverflowBox(
                          maxHeight: double.infinity,
                          maxWidth: double.infinity,
                          child: SizedBox(
                            width: width,
                            child: controller != null
                                ? CameraPreview(controller)
                                : const DecoratedBox(
                                    decoration: BoxDecoration(
                                      color: Colors.grey,
                                    ),
                                  ),
                          ),
                        ),
                      );
                    },
                  ),
                ),
              ),
            ),
            if (cameras != null)
              ...cameras.asMap().entries.map(
                    (entry) => Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: ElevatedButton(
                        onPressed: _isSwitching || entry.key == _index
                            ? null
                            : () => _switchCamera(entry.key, entry.value),
                        child: Text('cameras[${entry.key}]'),
                      ),
                    ),
                  )
            else
              const Padding(
                padding: EdgeInsets.all(8.0),
                child: Text('Loading cameras...'),
              )
          ],
        ),
      ),
    );
  }

  void _switchCamera(int index, CameraDescription camera) async {
    if (_isSwitching) return;

    setState(() {
      _controller = null;
      _index = index;
      _isSwitching = true;
    });

    final controller = CameraController(camera, ResolutionPreset.max);
    await controller.initialize();
    if (!mounted) {
      controller.dispose();
      return;
    }

    setState(() {
      _controller = controller;
      _isSwitching = false;
    });
  }
}