How to use iText with Flutter?

Overview

This guide demonstrates how to integrate iText into a Flutter application to natively generate PDFs on mobile devices.

👉 We will make use of Flutters MethodChannel class to bridge the code between Flutter, and the native Android code (Java) where iText runs.
👉 For iOS, you would need a back-end service to generate the PDFs (iText cannot run natively on iOS)

Prerequisites:

• Flutter SDK (all checks in flutter doctor should pass)

• IntelliJ or Android Studio

• Android device/emulator for testing (Android Device Manager)

• A valid iText license

• XCode (iOS Simulator) - For iOS

This is a simple Flutter application with a simple button that demonstrates the use of the iText API within a mobile application built with Flutter SDK.

Structure

• lib/main.dart : Flutter UI Page with a “Generate PDF” button.

• Native integration via MethodChannel to call Android code (this example provides Java integration, you may use Kotlin)

• MainActivity.Java (PDF logic with iText)

• A valid iText license

Step-by-Step Setup

1. lib/main.dart: The Dart code below defines a Button in Flutter UI that calls native Android methods to generate a PDF in the device’s local file system:

   DART

   import 'package:flutter/material.dart';
   import 'package:flutter/services.dart';
   
   void main() => runApp(MyApp());
   
   class MyApp extends StatelessWidget {
     static const platform = MethodChannel('flutter_pdf');
   
     Future<void> _generatePdf() async {
       try {
         final path = await platform.invokeMethod<String>('generatePdf');
         print('PDF created at: $path');
         _showDialog(path!);
       } catch (e) {
         print('Error: $e');
       }
     }
   
     void _showDialog(String path) {
       WidgetsBinding.instance.addPostFrameCallback((_) {
         showDialog(
           context: navigatorKey.currentContext!,
           builder: (_) => AlertDialog(
             title: Text("PDF Generated"),
             content: Text("Saved at:\n$path"),
             actions: [
               TextButton(child: Text("OK"), onPressed: () => Navigator.pop(navigatorKey.currentContext!))
             ],
           ),
         );
       });
     }
   
     static final navigatorKey = GlobalKey<NavigatorState>();
   
     @override
     Widget build(BuildContext context) {
       return MaterialApp(
         navigatorKey: navigatorKey,
         home: Scaffold(
           appBar: AppBar(title: Text("Flutter iText integration")),
           body: Center(
             child: ElevatedButton(
               onPressed: _generatePdf,
               child: Text("Generate PDF"),
             ),
           ),
         ),
       );
     }
   }

2. Adding iText dependencies & depository config
   👉 We need to first configure the iText dependencies, before we can move to Step 3 to write some code to perform iText operations.
   To add repository link:
   Path: android/build.gradle and then add:

   CODE

   allprojects {
       repositories {
           google()
           mavenCentral()
          maven {
              url = uri("https://repo.itextsupport.com/releases")
          }
       }
   }

   To add dependencies:
   Path: android/app/build.gradle and then add:

   CODE

   dependencies {
       implementation ("com.itextpdf:itext-core:9.2.0")
   }

3. Native Android code so our Flutter UI can communicate via MethodChannel to perform iText operations.
   Path : android/app/src/main/java/com/example/itextdemo/MainActivity.Java

   JAVA

   import android.os.Bundle;
   import io.flutter.embedding.android.FlutterActivity;
   import io.flutter.plugin.common.MethodChannel;
   
   import java.io.File;
   import java.io.FileOutputStream;
   
   import com.itextpdf.kernel.pdf.PdfWriter;
   import com.itextpdf.kernel.pdf.PdfDocument;
   import com.itextpdf.layout.Document;
   import com.itextpdf.layout.element.Paragraph;
   
   public class MainActivity extends FlutterActivity {
       private static final String CHANNEL = "flutter_pdf";
   
       @Override
       public void configureFlutterEngine(io.flutter.embedding.engine.FlutterEngine flutterEngine) {
           super.configureFlutterEngine(flutterEngine);
   
           new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
                   .setMethodCallHandler((call, result) -> {
                       if (call.method.equals("generatePdf")) {
                           try {
                               File file = new File(getCacheDir(), "sample_01.pdf");
                               PdfWriter writer = new PdfWriter(new FileOutputStream(file));
                               PdfDocument pdf = new PdfDocument(writer);
                               Document doc = new Document(pdf);
                               doc.add(new Paragraph("Hello from iText and Flutter!"));
                               doc.close();
                               result.success(file.getAbsolutePath());
                           } catch (Exception e) {
                               result.error("PDF_ERROR", e.getMessage(), null);
                           }
                       }
                   });
       }
   }

4. Run the application & test the PDF generation
   👉 Run flutter pub get in your IDE console
   👉 Start an Android emulator or connect a device
   👉 Run flutter run in your IDE console to start the app
   👉 Tap the Generate PDF Button in the UI → A sample PDF file will be saved to your device’s storage

Resources

➡️ iTextdemo.zip - Zip folder with a working basic Flutter & iText integration

➡️ sample_01.pdf- A sample generated PDF