fcs/lib/pages/sign.dart

import 'dart:typed_data';
import 'dart:ui' as ui;

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_signature_pad/flutter_signature_pad.dart';

class SignPage extends StatefulWidget {
  SignPage({Key key}) : super(key: key);

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

class _SignPageState extends State<SignPage> {
  ByteData _img = ByteData(0);
  var color = Colors.blue;
  var strokeWidth = 5.0;
  final _sign = GlobalKey<SignatureState>();

  @override
  void initState() {
    super.initState();
    SystemChrome.setPreferredOrientations([DeviceOrientation.landscapeLeft]);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.all(10.0),
            child: Text("Driver Signature"),
          ),
          Expanded(
            child: Container(
              child: Padding(
                padding: const EdgeInsets.all(8.0),
                child: Signature(
                  color: color,
                  key: _sign,
                  onSign: () {
                    final sign = _sign.currentState;
                  },
                  strokeWidth: strokeWidth,
                ),
              ),
              color: Colors.black12,
            ),
          ),
          _img.buffer.lengthInBytes == 0
              ? Container()
              : LimitedBox(
                  maxHeight: 200.0,
                  child: Image.memory(_img.buffer.asUint8List())),
          Column(
            children: <Widget>[
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: MaterialButton(
                        color: Colors.green,
                        onPressed: () async {
                          final sign = _sign.currentState;
                          final image = await sign.getData();
                          var data = await image.toByteData(
                              format: ui.ImageByteFormat.png);
                          Uint8List buffer = data.buffer.asUint8List();
                          // String path = await _localPath;
                          // File file = await new File(path + "/sign.png")
                          //     .writeAsBytes(buffer.asUint8List(
                          //         data.offsetInBytes, data.lengthInBytes));
                          Navigator.pop(context, buffer);
                        },
                        child: Text("OK")),
                  ),
                  Padding(
                    padding: const EdgeInsets.all(8.0),
                    child: MaterialButton(
                        color: Colors.grey,
                        onPressed: () {
                          final sign = _sign.currentState;
                          sign.clear();
                          setState(() {
                            _img = ByteData(0);
                          });
                        },
                        child: Text("Clear")),
                  ),
                ],
              ),
            ],
          )
        ],
      ),
    );
  }

}