用同步置pdf pdf插件以电子方式签名PDF

Question

我想以电子方式签名。因此，我使用签名 package package绘制签名，使用的可拖动窗口小部件可在PDF上放置在PDF上，并带有堆栈，使用 syncfusion_flutter_pdf 用于在pdf上绘制图像。当绘制图像以从可拖动小部件获得的偏移时，其绘图在不同的位置。我什至尝试将偏移从本地位置转换为全球位置，但仍然无法正常工作。

我知道代码很大，但无法避免任何行。任何帮助都会很棒

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

import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pdf_editing/helper/constants.dart';
import 'package:signature/signature.dart';
import 'package:syncfusion_flutter_pdf/pdf.dart';
import 'package:syncfusion_flutter_pdfviewer/pdfviewer.dart';

class PdfViewer extends StatefulWidget {
  PdfViewer({this.file});

  File? file;

  @override
  State<PdfViewer> createState() => _PdfViewerState();
}

class _PdfViewerState extends State<PdfViewer> {
  final controller = TextEditingController();
  Offset? _offset;
  bool isFixed = false;
  File? imageFile = File('');
  late File file;
  final _signatureController = SignatureController();
  Uint8List? _signatureBytes;
  int currentPage = 0;

  createFile() async {
    var dir = await getApplicationDocumentsDirectory();
    file = File('${dir.path}/doc.pdf');
    file.writeAsBytes(widget.file!.readAsBytesSync());
    setState(() {});
  }

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

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        appBar: AppBar(
          actions: [
            InkWell(
                onTap: () {
                  setState(() {
                    isFixed = false;
                  });
                  showSignatureDialogue();
                },
                child: Icon(Icons.edit)),
            sbw(20),
          ],
        ),
        body: SingleChildScrollView(
          child: Column(
            children: [
              PdfWidget(
                  file: file,
                  offset: _offset ?? Offset(37.5.w, 37.5.h),
                  signatureBytes: _signatureBytes,
                  isFixed: isFixed,
                  onDragEnd: (offset) {
                    _offset = offset;
                    setState(() {});
                  }),
            ],
          ),
        ),
      ),
    );
  }

  showSignatureDialogue() {
    showDialog(
        context: context,
        builder: (c) {
          return Dialog(
            insetPadding: EdgeInsets.symmetric(horizontal: 10, vertical: 100),
            child: Container(
              padding: EdgeInsets.all(20),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                children: [
                  Signature(
                    controller: _signatureController,
                    width: 300,
                    height: 300,
                    backgroundColor: Colors.yellow.withOpacity(0.2),
                  ),
                  Row(
                    children: [
                      TextButton(
                        onPressed: () {
                          _signatureController.clear();
                        },
                        child: Text('clear'),
                      ),
                      TextButton(
                        onPressed: () async {
                          final exportController = SignatureController(
                            penStrokeWidth: 2,
                            penColor: Colors.black,
                            exportBackgroundColor: Colors.white,
                            points: _signatureController.points,
                          );

                          _signatureBytes = await exportController.toPngBytes();

                          exportController.dispose();
                          setState(() {});
                          Navigator.pop(context);
                        },
                        child: Text('confirm'),
                      ),
                    ],
                  ),
                ],
              ),
            ),
          );
        });
  }
}

class PdfWidget extends StatefulWidget {
  PdfWidget({
    Key? key,
    this.signatureBytes,
    required this.file,
    required this.offset,
    required this.onDragEnd,
    required this.isFixed,
  }) : super(key: key);

  final Uint8List? signatureBytes;
  final File file;
  final Offset offset;
  final Function(Offset) onDragEnd;
  bool isFixed = false;

  @override
  State<PdfWidget> createState() => _PdfWidgetState();
}

class _PdfWidgetState extends State<PdfWidget> {
  int currentPage = 0;

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        Container(
          height: 70.h,
          child: SfPdfViewer.file(
            widget.file,
            onPageChanged: (page) {
              currentPage = page.newPageNumber;
              setState(() {});
            },
          ),
        ),
        Visibility(
          visible: widget.signatureBytes != null && !widget.isFixed,
          child: Positioned(
            top: widget.offset.dy,
            left: widget.offset.dx,
            child: Draggable(
              childWhenDragging: Container(),
              feedback: Material(
                child: imageWidget(),
              ),
              onDragEnd: (details) {
                RenderBox renderBox = context.findRenderObject() as RenderBox;
                var offset = renderBox.globalToLocal(details.offset);
                widget.onDragEnd(offset);
                setState(() {});
              },
              child: Column(
                children: [
                  imageWidget(),
                  Visibility(
                    visible: !widget.isFixed,
                    child: InkWell(
                        onTap: () {
                          final PdfDocument document = PdfDocument(
                              inputBytes: widget.file.readAsBytesSync());
                          final PdfBitmap image =
                              PdfBitmap(widget.signatureBytes!);
                          RenderBox renderBox =
                              context.findRenderObject() as RenderBox;
                          var offset = renderBox.localToGlobal(
                              Offset(widget.offset.dx, widget.offset.dy));
                          document.pages[currentPage].graphics.drawImage(
                              image,
                              Rect.fromLTWH(offset.dx, offset.dy, 100, 50)
                                  );
                          widget.file.writeAsBytes(document.save());
                          document.dispose();
                          widget.isFixed = true;
                          setState(() {});
                        },
                        child: Icon(Icons.done)),
                  )
                ],
              ),
            ),
          ),
        ),
      ],
    );
  }

  Widget imageWidget() {
    if (widget.signatureBytes != null) {
      return Image.memory(
        widget.signatureBytes!,
        height: 50,
        width: 100,
        fit: BoxFit.contain,
      );
    } else
      return Container();
  }
}