Merge PDF in Kotlin for Android

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/*
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 *   Copyright © 2020-2025 PSPDFKit GmbH. All rights reserved.
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 *
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 *   The PSPDFKit Sample applications are licensed with a modified BSD license.
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 *   Please see License for details. This notice may not be removed from this file.
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 */
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// We're temporarily suppressing the ProgressDialog being deprecated warning.
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// Issue: https://github.com/PSPDFKit/PSPDFKit/issues/32215
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@file:Suppress("DEPRECATION")
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package com.pspdfkit.catalog.examples.kotlin
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import android.app.ProgressDialog
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import android.content.Context
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import android.net.Uri
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import com.pspdfkit.catalog.R
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import com.pspdfkit.catalog.SdkExample
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import com.pspdfkit.configuration.activity.PdfActivityConfiguration
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import com.pspdfkit.document.DocumentSource
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import com.pspdfkit.document.PdfDocumentLoader
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import com.pspdfkit.document.processor.NewPage
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import com.pspdfkit.document.processor.PdfProcessor
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import com.pspdfkit.document.processor.PdfProcessorTask
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import com.pspdfkit.document.providers.AssetDataProvider
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import com.pspdfkit.ui.PdfActivity
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import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
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import io.reactivex.rxjava3.core.Single
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import io.reactivex.rxjava3.disposables.Disposable
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import io.reactivex.rxjava3.schedulers.Schedulers
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import java.io.File
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/**
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 * This example shows how to merge multiple PDFs using the document processor.
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 */
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class MergeDocumentsExample(context: Context) : SdkExample(context, R.string.mergeDocumentsExampleTitle, R.string.mergeDocumentsExampleDescription) {
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    /** Disposable for document merge operation of [com.pspdfkit.document.processor.PdfProcessor].*/
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    private var mergingDisposable: Disposable? = null
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    override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) {
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        val dialog = ProgressDialog.show(context, "Merging Documents", "Please wait", true, true) {
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            mergingDisposable?.dispose()
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        }
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        mergingDisposable = Single.fromCallable {
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            // Open the documents we are going to merge.
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            val documents = listOf("AnnualReport.pdf", "Scientific-Report.pdf", WELCOME_DOC)
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                .asSequence()
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                .map { PdfDocumentLoader.openDocument(context, DocumentSource(AssetDataProvider(it))) }
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            // Start with an empty document.
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            val task = PdfProcessorTask.empty()
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            // Add all document pages.
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            var totalPageCount = 0
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            for (document in documents) {
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                for (i in 0 until document.pageCount) {
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                    // We use `totalPageCount` here to add the pages to the end.
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                    // But you are free to add them at any place in the document you'd like.
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                    task.addNewPage(NewPage.fromPage(document, i).build(), totalPageCount)
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                    totalPageCount++
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                }
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            }
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            // Finally create the resulting document.
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            val mergedDocumentsFile = File(context.getDir("documents", Context.MODE_PRIVATE), "merged-documents.pdf")
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            PdfProcessor.processDocument(task, mergedDocumentsFile)
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            return@fromCallable Uri.fromFile(mergedDocumentsFile)
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        }.subscribeOn(Schedulers.io())
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            .observeOn(AndroidSchedulers.mainThread())
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            .doFinally { dialog.cancel() }
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            .subscribe { uri -> PdfActivity.showDocument(context, uri, configuration.build()) }
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    }
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}