[移动开发]flutter 画板签名 下载文件 上传

import 'dart:io';
import 'dart:typed_data';

import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:signature/signature.dart';
import 'package:tg/providers/flutter/permission.dart';
import 'package:tg/providers/http/uploadfile.dart';

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

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

class _SignaturePageState extends State<SignaturePage> {
  final SignatureController _controller = SignatureController(
    penStrokeWidth: 1,
    penColor: Colors.black,
    exportBackgroundColor: Colors.blue,
  );

  ///下载文件
  Future<File> getFile(data) async {
    checkPermissionStorage(); //申请权限
    final filename = DateTime.now().millisecondsSinceEpoch;
    Directory directory = await getApplicationDocumentsDirectory();
    String dir = directory.path;
    File file = new File('$dir/$filename');
    await file.writeAsBytes(data);
    return file;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(
            "签字确认",
            style: TextStyle(fontSize: 16),
          ),
          centerTitle: true,
          toolbarHeight: 40,
        ),
        body: ListView(
          children: <Widget>[
            Signature(
              controller: _controller,
              height: 500,
              backgroundColor: Colors.white,
            ),
            //OK AND CLEAR BUTTONS
            Container(
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                mainAxisSize: MainAxisSize.max,
                children: <Widget>[
                  Expanded(
                      child: Container(
                          height: 40,
                          margin: EdgeInsets.all(10),
                          child: FloatingActionButton(
                            shape: RoundedRectangleBorder(
                                borderRadius: BorderRadius.circular(10)),
                            heroTag: 1,
                            onPressed: () async {
                              // if (_controller.isNotEmpty) {
                              final Uint8List data =
                                  await _controller.toPngBytes();
                              File file = await getFile(data);
                              uploadFile(file); //上传文件
                              // 预览
                              // if (data != null) {
                              //   await Navigator.of(context).push(
                              //     MaterialPageRoute<void>(
                              //       builder: (BuildContext context) {
                              //         return Scaffold(
                              //           appBar: AppBar(
                              //             title: Text(
                              //               "预览",
                              //               style: TextStyle(fontSize: 16),
                              //             ),
                              //             centerTitle: true,
                              //             toolbarHeight: 40,
                              //           ),
                              //           body: Center(
                              //             child: Container(
                              //               color: Colors.white,
                              //               child: Image.file(file),
                              //             ),
                              //           ),
                              //         );
                              //       },
                              //     ),
                              //   );
                              // }
                            },
                            child: Text("确定"),
                          ))),
                  Expanded(
                      child: Container(
                          height: 40,
                          margin: EdgeInsets.all(10),
                          child: FloatingActionButton(
                            shape: RoundedRectangleBorder(
                                borderRadius: BorderRadius.circular(10)),
                            heroTag: 2,
                            onPressed: () async {
                              setState(() => _controller.clear());
                            },
                            child: Text("重写"),
                          )))
                ],
              ),
            ),
          ],
        ));
  }
}