How to Add Unicode Text in the PDF Text Box Fields Using Flutter

The Flutter PDF library is used to create, read, and edit PDF documents programmatically without Adobe dependencies. Using this library, you can draw Unicode text in text box fields in a PDF document using Flutter.

Steps to draw Unicode text in text box fields programmatically

1. Create a new Flutter application project.

   1. Open Visual Studio Code (After installing the Dart and Flutter extensions as stated in this setup editor page).
   2. Click View -> Command Palette.
   3. Type Flutter and choose Flutter: New Project.
   4. Enter the project name and press** Enter**.
   5. Now, choose the location of the project.

2. Add the following code in your pubspec.yaml file to install the syncfusion® flutter pdf package in your application. It will be automatically downloaded from the pub once you trigger the flutter pub to get comments. or the Get packages option from the Visual Studio code.

dependencies:
syncfusion_flutter_pdf: ^25.1.39

3. Import the following package in your main.dart file.

import 'package:syncfusion_flutter_pdf/pdf.dart';

4. Add the following code in lib/main.dart file to create a simple button.

@override
 Widget build(BuildContext context) {
   return Scaffold(
     appBar: AppBar(
       backgroundColor: Theme.of(context).colorScheme.inversePrimary,
       title: Text(widget.title),
     ),
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
           TextButton(
             child: Text(
               'Draw unicode text in text box field',
               style: TextStyle(color: Colors.white),
             ),
             style: ButtonStyle(
                 backgroundColor: MaterialStateProperty.resolveWith(
                     (states) => Colors.blue)),
             onPressed: drawUnicode,
           )
         ],
       ),
     ),
   );
 }

5. Include the following code sample in the drawUnicode method to draw Unicode text in text box fields.

Future<void> drawUnicode() async {
   //Load the existing PDF document.
   final PdfDocument loadedDocument =
       PdfDocument(inputBytes: await _readData('Input.pdf'));
   // Access the form fields of the loaded document.
   PdfForm loadedForm = loadedDocument.form;
   //Create Unicode font to render the Unicode characters in text box fields.
   PdfTrueTypeFont unicodeFont = PdfTrueTypeFont(await _readData('arial.ttf'), 14);
   // Iterate through each field in the form.
   for (int i = 0; i < loadedForm.fields.count; i++) {
     PdfField field = loadedForm.fields[i];
     // Check if the field is a text box field.
     if (field is PdfTextBoxField) {
       // Set the text of the field to include the Unicodee text.
       field.text = 'ä, ü, ï, ö, ë, ÿ';
       // Set the font for the field
       field.font = unicodeFont;
     }
   }
   // Disable the default appearance for the form fields.
   loadedForm.setDefaultAppearance(false);
   //Save the document.
   List<int> bytes = await loadedDocument.save();
   // Dispose the document.
   loadedDocument.dispose();
   //Save the file and launch/download.
   SaveFile.saveAndLaunchFile(bytes, 'output.pdf');
 }

6. Use the following code to load the PDF file in the Flutter project.

a. Add the following code in your pubspec.yaml file.

flutter:
# To add assets to your application, add an assets section, like this:
assets:
  - assets/

b. Import the following package in your main.dart file.

import 'package:flutter/services.dart';

c. Add the following code in the lib/main.dart file to read the existing PDF file.

Future<List<int>> _readData(String name) async {
final ByteData data = await rootBundle.load('assets/$name');
return data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
}

7. Follow these steps to launch the generated PDF file on desktop, mobile, and web platforms.

Web

a. Add the web package as a dependency in your pubspec.yaml file. Then, create a new Dart file named save_file_web.dart. Finally, add the following code to implement the file download functionality using the web package.

import 'dart:convert';
import 'package:web/web.dart' as web;

b. To enable file saving and initiate downloads in a Flutter web environment, use the following code within the saveAndLaunchFile method.

// Function to save and launch a file for download in a web environment
Future<void> saveAndLaunchFile(List<int> bytes, String fileName) async {
 final web.HTMLAnchorElement anchor =
     web.document.createElement('a') as web.HTMLAnchorElement
       ..href = "data:application/octet-stream;base64,${base64Encode(bytes)}"
       ..style.display = 'none'
       ..download = fileName;

// Insert the new element into the DOM
web.document.body!.appendChild(anchor);

// Initiate the download
anchor.click();
// Clean up the DOM by removing the anchor element
web.document.body!.removeChild(anchor);
}

Desktop and mobile:

a. Add the following dependencies in your pubspec.yaml file.

open_file: ^3.2.1
path_provider: ^2.0.11 #Open source library to launch the PDF file on mobile devices

b. Create a new dart file named save_file_mobile_and_desktop.dart under the lib folder and import the following packages in save_file_mobile_and_desktop.dart file.

import 'dart:io';
import 'package:open_file/open_file.dart';
import 'package:path_provider/path_provider.dart';

c. Include the following code snippet in save_file_mobile_and_desktop.dart to open a PDF document in Desktop and Mobile.

class SaveFile {
static Future<void> saveAndLaunchFile(
    List<int> bytes, String fileName) async {
  //Get external storage directory.
  Directory directory = await getApplicationSupportDirectory();
  //Get directory path.
  String path = directory.path;
  //Create an empty file to write the PDF data.
  File file = File('$path/$fileName');
  //Write the PDF data.
  await file.writeAsBytes(bytes, flush: true);
  //Open a PDF document on mobile.
  OpenFile.open('$path/$fileName');
}
}

8. Run the sample using the flutter run command. After the application launches, you will get a PDF document as follows.

A complete working sample can be downloaded from insertPageFromAnotherPDF.zip.

Take a moment to peruse the documentation for working with Text, where you can find the other options like drawing right-to-left text, multicolumn text, consuming TrueType fonts, Standards fonts, and CJK fonts.

Click here to explore the rich set of Syncfusion Essential® PDF features.