Importing and exporting data in Xamarin Pdf Viewer (SfPdfViewer)

5 Dec 20225 minutes to read

Xamarin PDF Viewer provides options to import and export data like form fields and annotations in the PDF document.

Importing and exporting form data

The import and export of form data supports the following extensions.

• fdf
• xfdf
• json
• xml

The required file type can be chosen from the DataFormat enumeration. In the following sections only the fdf file type is explained for brevity.

Exporting form data

The ExportFormData method exports the current data filled in the form fields into a stream in the specified file format. The name of the PDF (with extension) from which the data are exported should be given as the second argument to the method.

C#

//Export form data to "fdf" data format
Stream fdfStreamToSave = pdfViewerControl.ExportFormData(DataFormat.Fdf, "PdfFileName.fdf");

NOTE

While saving the stream returned by the ExportFormData method, the file name must have the same extension as the file type that was given as the first argument. For example, in the above case the file type provided is fdf, so the saved file extension should be .fdf.

Importing form data

The ImportFormData method imports the data from a file of specified type and fills the saved data into the form fields.

C#

//Import form data from "fdf" data format
Stream fdfStreamToImport = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("SampleDefaultNamespace.Assets.PdfFileName.fdf");
pdfViewerControl.ImportFormData(fdfStreamToImport, DataFormat.Fdf);

Importing and exporting annotations

The import and export of annotations support following extensions.

• fdf
• xfdf

The required file type can be chosen from the DataFormat enumeration. In the following sections only the fdf file type is explained for brevity.

Exporting annotations

The ExportAnnotations method exports the current annotations added to the document into a stream in the specified file format.

C#

//Export annotations to "FDF" data format
Stream fdfStreamToSave = pdfViewerControl.ExportAnnotations(AnnotationDataFormat.Fdf);

A selective list of annotations can also be exported in the specified file format using the ExportAnnotations overload method . The annotations list needs to be exported, and the data format should be passed as method arguments. The following code example explains exporting the list of annotations present only on the first page.

C#

//Get the list of annotations present on the first page
List<IAnnotation> firstPageAnnotations = pdfViewerControl.Annotations.Where(annotation => annotation.PageNumber == 1).ToList();
//Export annotations to "FDF" data format
Stream fdfStreamToSave = pdfViewerControl.ExportAnnotations(firstPageAnnotations, AnnotationDataFormat.Fdf);

NOTE

The ExportAnnotations method does not preserve the stamp annotations on export function. Instead, use the ExportAnnotationsAsync method to preserve them.

Export annotations asynchronously

The PDF Viewer allows you to export the current annotations added to a document into a stream asynchronously using the ExportAnnotationsAsync method. You can also cancel the asynchronous annotation exporting when it is in progress.

C#

//Export the annotations asynchronously to the "FDF" data format 
Stream fdfStreamToSave = await pdfViewerControl.ExportAnnotationsAsync(AnnotationDataFormat.Fdf, cancellationTokenSource);

A selective list of annotations can also be exported asynchronously in the specified file format using the ExportAnnotationsAsync overload method. The annotations list needs to be exported, and the data format should be passed as method arguments. The following code example explains exporting the list of annotations asynchronously present only on the first page.

C#

//Get the list of annotations present in the first page
List<IAnnotation> firstPageAnnotations = pdfViewerControl.Annotations.Where(annotation => annotation.PageNumber == 1).ToList();
//Export the annotations asynchronously to the "FDF" data format 
Stream fdfStreamToSave = await pdfViewerControl.ExportAnnotationsAsync(firstPageAnnotations, AnnotationDataFormat.Fdf, cancellationTokenSource);

In the above code samples, the cancellationTokenSource enables you to cancel the asynchronous annotation exporting when it is in progress.

Cancel the asynchronous annotations exporting

You can raise the cancel request when the annotations exporting is in progress

C#

private void cancelButton_Clicked(object sender, EventArgs e)
 { 
   cancellationTokenSource.Cancel();
 }

In the above code sample, the cancellationTokenSource instance is the same as the one given as the argument when exporting the annotations asynchronously.

NOTE

Calling the above method will not have any effect once the annotations are completely exported. It will stop the exporting process only when it is in progress.

Importing annotations

The ImportAnnotations method imports the annotations from the file of specified type and fills the saved annotations into the loaded PDF document.

C#

//Import annotations from "fdf" data format
Stream fdfStreamToImport = typeof(App).GetTypeInfo().Assembly.GetManifestResourceStream("SampleDefaultNamespace.Assets.PdfFileName.fdf");
pdfViewerControl.ImportAnnotations(fdfStreamToImport, AnnotationDataFormat.Fdf);

NOTE

You can also explore our Xamarin.Forms PDF Viewer example to knows the functionalities of each feature.