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PDF page labels in Kotlin

Sample Kotlin code for using PDFTron SDK to work with PDF page labels. PDF page labels can be used to describe a page, which is used to allow for non-sequential page numbering or the addition of arbitrary labels for a page (such as the inclusion of Roman numerals at the beginning of a book). Learn more about our PDF Editing & Manipulation Library.

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//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

package com.pdftron.android.pdfnetsdksamples.samples

import com.pdftron.android.pdfnetsdksamples.OutputListener
import com.pdftron.android.pdfnetsdksamples.PDFNetSample
import com.pdftron.android.pdfnetsdksamples.R
import com.pdftron.android.pdfnetsdksamples.util.Utils
import com.pdftron.pdf.PDFDoc
import com.pdftron.pdf.PageLabel
import com.pdftron.sdf.SDFDoc
import java.util.*

/**
 * The sample illustrates how to work with PDF page labels.
 *
 *
 * PDF page labels can be used to describe a page. This is used to
 * allow for non-sequential page numbering or the addition of arbitrary
 * labels for a page (such as the inclusion of Roman numerals at the
 * beginning of a book). PDFNet PageLabel object can be used to specify
 * the numbering style to use (for example, upper- or lower-case Roman,
 * decimal, and so forth), the starting number for the first page,
 * and an arbitrary prefix to be pre-appended to each number (for
 * example, "A-" to generate "A-1", "A-2", "A-3", and so forth.)
 */
class PageLabelsTest : PDFNetSample() {
    init {
        setTitle(R.string.sample_pagelabels_title)
        setDescription(R.string.sample_pagelabels_description)
    }

    override fun run(outputListener: OutputListener?) {
        super.run(outputListener)
        mOutputListener = outputListener
        mFileList.clear()
        printHeader(outputListener!!)

        try {
            //-----------------------------------------------------------
            // Example 1: Add page labels to an existing or newly created PDF
            // document.
            //-----------------------------------------------------------
            run {
                val doc = PDFDoc(Utils.getAssetTempFile(PDFNetSample.INPUT_PATH + "newsletter.pdf")!!.absolutePath)
                doc.initSecurityHandler()

                // Create a page labeling scheme that starts with the first page in
                // the document (page 1) and is using uppercase roman numbering
                // style.
                doc.setPageLabel(1, PageLabel.create(doc, PageLabel.e_roman_uppercase, "My Prefix ", 1))

                // Create a page labeling scheme that starts with the fourth page in
                // the document and is using decimal arabic numbering style.
                // Also the numeric portion of the first label should start with number
                // 4 (otherwise the first label would be "My Prefix 1").
                val L2 = PageLabel.create(doc, PageLabel.e_decimal, "My Prefix ", 4)
                doc.setPageLabel(4, L2)

                // Create a page labeling scheme that starts with the seventh page in
                // the document and is using alphabetic numbering style. The numeric
                // portion of the first label should start with number 1.
                val L3 = PageLabel.create(doc, PageLabel.e_alphabetic_uppercase, "My Prefix ", 1)
                doc.setPageLabel(7, L3)

                doc.save(Utils.createExternalFile("newsletter_with_pagelabels.pdf", mFileList).absolutePath, SDFDoc.SaveMode.LINEARIZED, null)
                doc.close()
                mOutputListener!!.println("Done. Result saved in newsletter_with_pagelabels.pdf...")
            }

            //-----------------------------------------------------------
            // Example 2: Read page labels from an existing PDF document.
            //-----------------------------------------------------------
            run {
                val doc = PDFDoc(Utils.createExternalFile("newsletter_with_pagelabels.pdf", mFileList).absolutePath)
                doc.initSecurityHandler()

                var label: PageLabel
                val page_num = doc.pageCount
                for (i in 1..page_num) {
                    mOutputListener!!.println("Page number: $i")
                    label = doc.getPageLabel(i)
                    if (label.isValid) {
                        mOutputListener!!.println(" Label: " + label.getLabelTitle(i))
                    } else {
                        mOutputListener!!.println(" No Label.")
                    }
                }
                doc.close()
            }

            //-----------------------------------------------------------
            // Example 3: Modify page labels from an existing PDF document.
            //-----------------------------------------------------------
            run {
                val doc = PDFDoc(Utils.createExternalFile("newsletter_with_pagelabels.pdf", mFileList).absolutePath)
                doc.initSecurityHandler()

                // Remove the alphabetic labels from example 1.
                doc.removePageLabel(7)

                // Replace the Prefix in the decimal lables (from example 1).
                var label = doc.getPageLabel(4)
                if (label.isValid) {
                    label.prefix = "A"
                    label.start = 1
                }

                // Add a new label
                val new_label = PageLabel.create(doc, PageLabel.e_decimal, "B", 1)
                doc.setPageLabel(10, new_label)  // starting from page 10.

                doc.save(Utils.createExternalFile("newsletter_with_pagelabels_modified.pdf", mFileList).absolutePath, SDFDoc.SaveMode.LINEARIZED, null)
                mOutputListener!!.println("Done. Result saved in newsletter_with_pagelabels_modified.pdf...")

                val page_num = doc.pageCount
                for (i in 1..page_num) {
                    mOutputListener!!.print("Page number: $i")
                    label = doc.getPageLabel(i)
                    if (label.isValid) {
                        mOutputListener!!.println(" Label: " + label.getLabelTitle(i))
                    } else {
                        mOutputListener!!.println(" No Label.")
                    }
                }
                doc.close()
            }

            //-----------------------------------------------------------
            // Example 4: Delete all page labels in an existing PDF document.
            //-----------------------------------------------------------
            run {
                val doc = PDFDoc(Utils.createExternalFile("newsletter_with_pagelabels.pdf", mFileList).absolutePath)
                doc.root.erase("PageLabels")
                // ...
                doc.close()
            }
        } catch (e: Exception) {
            mOutputListener!!.printError(e.stackTrace)
        }

        for (file in mFileList) {
            addToFileList(file)
        }
        printFooter(outputListener)
    }

    companion object {

        private var mOutputListener: OutputListener? = null

        private val mFileList = ArrayList<String>()
    }

}
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