Flutter 为什么'；这不会显示下一个pdf，但始终显示第一个pdf吗？

我是个新手。我正在做一个项目，它必须根据用户输入创建PDF。在第一次输入中，它创建PDF并预览它。但在接下来的输入中，它不会显示新的PDF，而是显示旧的PDF。我不知道怎么了

我用来预览和创建pdf的包

import 'package:flutter_full_pdf_viewer/full_pdf_viewer_scaffold.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

final pdf = pw.Document();

  writeOnPdf() {
    String name = controllerName.text;
    String drugs = controllerDrugs.text;
    pdf.addPage(pw.MultiPage(
        pageFormat: PdfPageFormat.a4,
        margin: pw.EdgeInsets.all(32),
        build: (pw.Context context) {
          return <pw.Widget>[
            pw.Header(level: 0, child: pw.Text("Methsuwa Family Clinics", 
style: pw.TextStyle(fontSize: 40)) ),
            pw.Header(child: pw.Text('Name :- ' + name, style: 
pw.TextStyle(fontSize:16))),
        pw.Paragraph(text: 'Medications :-'),
        pw.Paragraph(text: drugs)
          ];
        }));
  }

  Future savePdf() async {
    String name = controllerName.text;
    Directory documentDirectory = await getApplicationDocumentsDirectory();

    String documentPath = documentDirectory.path;
    File file = File("$documentPath/" + name + ".pdf");
    file.writeAsBytesSync(await pdf.save());
}

创建pdf的代码

import 'package:flutter_full_pdf_viewer/full_pdf_viewer_scaffold.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

final pdf = pw.Document();

  writeOnPdf() {
    String name = controllerName.text;
    String drugs = controllerDrugs.text;
    pdf.addPage(pw.MultiPage(
        pageFormat: PdfPageFormat.a4,
        margin: pw.EdgeInsets.all(32),
        build: (pw.Context context) {
          return <pw.Widget>[
            pw.Header(level: 0, child: pw.Text("Methsuwa Family Clinics", 
style: pw.TextStyle(fontSize: 40)) ),
            pw.Header(child: pw.Text('Name :- ' + name, style: 
pw.TextStyle(fontSize:16))),
        pw.Paragraph(text: 'Medications :-'),
        pw.Paragraph(text: drugs)
          ];
        }));
  }

  Future savePdf() async {
    String name = controllerName.text;
    Directory documentDirectory = await getApplicationDocumentsDirectory();

    String documentPath = documentDirectory.path;
    File file = File("$documentPath/" + name + ".pdf");
    file.writeAsBytesSync(await pdf.save());
}

调用pdf

     onPressed: () async {

          String name = controllerName.text;

          // Add your onPressed code here!
          writeOnPdf();
          await savePdf();

          Directory documentDirectory =
              await getApplicationDocumentsDirectory();
          String documentPath = documentDirectory.path;
          String fullPath = ("$documentPath/" + name + ".pdf"); // name is the file name which user inputs.

          Navigator.push(
              context,
              MaterialPageRoute(
                  builder: (context) => PdfPreviewScreen(path: fullPath)));

这是PDF显示类

class PdfPreviewScreen extends StatelessWidget{
    final String path;
  
    PdfPreviewScreen({this.path});
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar:AppBar(
          leading: IconButton(
            icon: Icon(Icons.menu),
            onPressed: null,
            tooltip: "Navigation Menu",
          ),
          title: Text("Methsuwa Family Clinics"),
        ),
        body: PDFViewerScaffold(path: path),
      );
    }
  }

final pdf=pw.Document（）；
writeOnPdf（）{
字符串名称=controllerName.text；
字符串药物=controllerDrugs.text；
pdf.addPage（pw.MultiPage(
页面格式：PdfPageFormat.a4，
裕度：所有边缘集（32），
构建：（pw.Context）{
返回[
pw.Header（级别：0，儿童：pw.Text（“Methsuwa家庭诊所”），
样式：pw.TextStyle（fontSize:40）），
pw.Header（子项：pw.Text（'Name:-'）+名称，样式：
pw.TextStyle（fontSize:16）），
pw.段落（正文：“药物：-”），
pw.第段（正文：药物）
];
}));
}

---

在这里，当我想要创建时，我会一次又一次地更新同一个名为pdf的变量。不仅如此，我还创建了多页pdf。所以我每次运行它都会创建一个新页面。这就是我的代码的问题。

以下是每次使用新pdf的完整工作代码：

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:open_file/open_file.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pdf/pdf.dart';
import 'package:pdf/widgets.dart' as pw;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyStatefulWidget(),
    );
  }
}

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

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

class _MyStatefulWidgetState extends State<MyStatefulWidget> {
  final nameText = TextEditingController();
  final drugsText = TextEditingController();

  @override
  void dispose() {
    nameText.dispose();
    drugsText.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              TextField(
                controller: nameText,
                decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter Name',
                ),
              ),
              TextField(
                controller: drugsText,
                decoration: InputDecoration(
                  border: OutlineInputBorder(),
                  hintText: 'Enter Drug',
                ),
              ),
              TextButton(
                onPressed: () async {
                  String name = nameText.text;
                  String drugs = drugsText.text;

                  var pdf = pw.Document(); //pdf document
                  
                  // Pdf creation
                  writeOnPdf() {
                    pdf.addPage(pw.MultiPage(
                        pageFormat: PdfPageFormat.a4,
                        margin: pw.EdgeInsets.all(32),
                        build: (pw.Context context) {
                          return <pw.Widget>[
                            pw.Header(
                                level: 0,
                                child: pw.Text("Methsuwa Family Clinics",
                                    style: pw.TextStyle(fontSize: 40))),
                            pw.Header(
                                child: pw.Text('Name :- ' + name,
                                    style: pw.TextStyle(fontSize: 16))),
                            pw.Paragraph(text: 'Medications :-'),
                            pw.Paragraph(text: drugs)
                          ];
                        }));
                  }

                  //Saving pdf
                  Future savePdf() async {
                    Directory documentDirectory =
                        await getApplicationDocumentsDirectory();

                    String documentPath = documentDirectory.path;
                    File file = File("$documentPath/" + name + ".pdf");
                    file.writeAsBytesSync(await pdf.save());
                  }


                  writeOnPdf();
                  await savePdf();

                  Directory documentDirectory =
                      await getApplicationDocumentsDirectory();
                  String documentPath = documentDirectory.path;
                  String fullPath = ("$documentPath/" + name + ".pdf");

                  //Opening created pdf
                  OpenFile.open(fullPath);
                },
                child: Text('Click To Create PDF'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

---

还请澄清您用于创建和查看pdf的包装。同时添加创建pdf的代码。@DC很抱歉出错。感谢提供更多信息，但您仍然忘记提供创建pdf的输入方式。我想是用了

writeOnPdf（）

。@DC我很抱歉没有提供必要的细节。很高兴你发现了这个问题。起初，我认为您希望新数据以相同的pdf格式显示，但作为新页面。