[syncfusion_flutter_pdf] Can not insert a page at specific index

[marcsanny]

Bug description

We are not able to insert a page at specific index (add() method works as expected). We get: Null check operator used on a null value
It seems like the line is causing the error:

Steps to reproduce

1. Create document
2. Insert page

Code sample

Minimal reproducible code:

Code sample

    final doc = PdfDocument();
    doc.pages.insert(0);

[irfanajaffer]

Hi @marcsanny ,

Yes, it's possible to insert a PDF page at a specific index in a newly created PDF document using Syncfusion Flutter PDF package. There are a couple of ways to achieve this based on your requirements.

Method 1: Inserting an Empty Page at a Specific Index

You can insert an empty page at any specific index in a PDF document using the insert method:

---

//Create a new PDF document

PdfDocument document = PdfDocument();

 

//Add some initial content

document.pages.add().graphics.drawString(

    'First Page',

    PdfStandardFont(PdfFontFamily.helvetica, 20)

);

 

//Insert a new empty page at index 1 (second position)

document.pages.insert(1);

 

//Add content to the third page

document.pages.add().graphics.drawString(

    'Third Page',

    PdfStandardFont(PdfFontFamily.helvetica, 20)

);

 

//Save and dispose the PDF document

File('output.pdf').writeAsBytes(await document.save());

document.dispose();

---

Method 2: Inserting a Page from Another PDF Document

To insert a page from an existing PDF at a specific index in your document:

---

Future _insertPdf() async {

   //Load the existing PDF document

   final PdfDocument sourceDocument =

       PdfDocument(inputBytes: await _readPdfDocumentData('barcode.pdf'));

  

   //Get the page if you want to insert another PDF

   PdfPage page = sourceDocument.pages[0];

  

   //Create the page as template

   PdfTemplate template = page.createTemplate();

  

   //Load the target document

   PdfDocument destDocument =

       PdfDocument(inputBytes: await _readPdfDocumentData('invoice.pdf'));

  

   //Add new page to the document at a specific index (e.g., index 1)

   PdfPage destPage = destDocument.pages.insert(1);

  

   //Draw the template on the new page

   destPage.graphics

       .drawPdfTemplate(template, const Offset(0, 0), destPage.size);

 

   //Save the document

   List<int> bytes = await destDocument.save();

  

   // Dispose both the documents

   destDocument.dispose();

   sourceDocument.dispose();

 

   //Save the file and launch/download

   SaveFile.saveAndLaunchFile(bytes, 'output.pdf');

}

---

The key part is using document.pages.insert(index) to add an empty page at the specified index, or you can use it to insert and then immediately add content from another PDF document using templates.

To read PDF files from your Flutter project, you'll need to set up proper file handling as
shown in the included helper method:

---

Future<List<int>> _readPdfDocumentData(String name) async {

  final ByteData data = await rootBundle.load('assets/pdf/$name');

  return data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);

}

---

This allows you to insert pages from existing PDFs at specific indexes in your newly created PDF document

[irfanajaffer]

Please share with us your complete requirements so that we can assist with you further in this