r_scan/example/lib/scan_camera_dialog.dart

import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:r_scan_example/scan_dialog.dart';
import 'package:r_scan/src/r_scan_camera.dart';

List<RScanCameraDescription> rScanCameras;

class RScanCameraDialog extends StatefulWidget {
  @override
  _RScanCameraDialogState createState() => _RScanCameraDialogState();
}

class _RScanCameraDialogState extends State<RScanCameraDialog> {
  RScanCameraController _controller;
  bool isFirst = true;

  void initCamera() async {
    if (rScanCameras == null || rScanCameras.length == 0) {
      final result = await PermissionHandler()
          .checkPermissionStatus(PermissionGroup.camera);
      if (result == PermissionStatus.granted) {
        rScanCameras = await availableRScanCameras();
        print('返回可用的相机：${rScanCameras.join('\n')}');
      } else {
        final resultMap = await PermissionHandler()
            .requestPermissions([PermissionGroup.camera]);
        if (resultMap[PermissionGroup.camera] == PermissionStatus.granted) {
          rScanCameras = await availableRScanCameras();
        } else {
          print('相机权限被拒绝，无法使用');
        }
      }
    }
    if (rScanCameras != null && rScanCameras.length > 0) {
      _controller = RScanCameraController(
          rScanCameras[0], RScanCameraResolutionPreset.high)
        ..addListener(() {
          final result = _controller.result;
          if (result != null) {
            if (isFirst) {
              Navigator.of(context).pop(result);
              isFirst = false;
            }
          }
        })
        ..initialize().then((_) {
          if (!mounted) {
            return;
          }
          setState(() {});
        });
    }
  }

  @override
  void initState() {
    super.initState();
    initCamera();
  }

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

  @override
  Widget build(BuildContext context) {
    if (rScanCameras == null || rScanCameras.length == 0) {
      return Scaffold(
        body: Container(
          alignment: Alignment.center,
          child: Text('not have available camera'),
        ),
      );
    }
    if (!_controller.value.isInitialized) {
      return Container();
    }
    return Scaffold(
      backgroundColor: Colors.black,
      body: Stack(
        children: <Widget>[
          ScanImageView(
            child: AspectRatio(
              aspectRatio: _controller.value.aspectRatio,
              child: RScanCamera(_controller),
            ),
          ),
          Align(
              alignment: Alignment.bottomCenter,
              child: FutureBuilder(
                future: getFlashMode(),
                builder: _buildFlashBtn,
              ))
        ],
      ),
    );
  }

  Future<bool> getFlashMode() async {
    bool isOpen = false;
    try {
      isOpen = await _controller.getFlashMode();
    } catch (_) {}
    return isOpen;
  }

  Widget _buildFlashBtn(BuildContext context, AsyncSnapshot<bool> snapshot) {
    return snapshot.hasData
        ? Padding(
            padding: EdgeInsets.only(
                bottom: 24 + MediaQuery.of(context).padding.bottom),
            child: IconButton(
                icon: Icon(snapshot.data ? Icons.flash_on : Icons.flash_off),
                color: Colors.white,
                iconSize: 46,
                onPressed: () {
                  if (snapshot.data) {
                    _controller.setFlashMode(false);
                  } else {
                    _controller.setFlashMode(true);
                  }
                  setState(() {});
                }),
          )
        : Container();
  }
}