--- title: "Document Comparison" canonical_url: "https://www.nutrient.io/guides/android/samples/document-comparison-kotlin/" md_url: "https://www.nutrient.io/guides/android/samples/document-comparison-kotlin.md" last_updated: "2026-05-15T19:10:04.916Z" description: "Compare two PDFs side-by-side with different stroke colors for each document." --- # Document Comparison Compare two PDFs side-by-side with different stroke colors for each document. [Get Started](https://www.nutrient.io/sdk/android/getting-started.md) [All Samples](https://www.nutrient.io/guides/android/samples.md) [Download](https://www.nutrient.io/guides/android/downloads.md) [Launch Demo](https://www.nutrient.io/demo/) --- ```kotlin /* * Copyright © 2018-2026 PSPDFKit GmbH. All rights reserved. * * The PSPDFKit Sample applications are licensed with a modified BSD license. * Please see License for details. This notice may not be removed from this file. */ // We're temporarily suppressing the ProgressDialog being deprecated warning. // Issue: https://github.com/PSPDFKit/PSPDFKit/issues/32215 @file:Suppress("DEPRECATION") package com.pspdfkit.catalog.examples.kotlin import android.annotation.SuppressLint import android.app.ProgressDialog import android.content.Context import android.net.Uri import android.os.Build import android.os.Bundle import android.util.Log import android.util.TypedValue import android.view.Gravity import android.view.WindowInsets import android.widget.RelativeLayout import android.widget.Toast import androidx.core.graphics.toColorInt import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton import com.pspdfkit.annotations.BlendMode import com.pspdfkit.catalog.R import com.pspdfkit.catalog.SdkExample import com.pspdfkit.configuration.activity.PdfActivityConfiguration import com.pspdfkit.configuration.activity.ThumbnailBarMode import com.pspdfkit.configuration.sharing.ShareFeatures import com.pspdfkit.document.DocumentSource import com.pspdfkit.document.PdfDocument import com.pspdfkit.document.PdfDocumentLoader import com.pspdfkit.document.processor.ComparisonDialogListener import com.pspdfkit.document.processor.ComparisonDocument import com.pspdfkit.document.processor.DocumentComparisonDialog import com.pspdfkit.document.processor.PagePdf import com.pspdfkit.document.processor.PdfProcessor import com.pspdfkit.document.processor.PdfProcessorTask import com.pspdfkit.document.providers.AssetDataProvider import com.pspdfkit.ui.DocumentDescriptor import com.pspdfkit.ui.PdfActivity import com.pspdfkit.ui.PdfActivityIntentBuilder import com.pspdfkit.ui.tabs.PdfTabBarCloseMode import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers import io.reactivex.rxjava3.core.Single import io.reactivex.rxjava3.functions.Consumer import io.reactivex.rxjava3.schedulers.Schedulers import java.io.File import java.util.EnumSet /** * This example shows how to use [PdfProcessor] for comparing PDF pages using a different * stroke color for each and blending these colored pages into a single document. Furthermore, it shows how to integrate the * {@link com.pspdfkit.document.processor.DocumentComparisonDialog} to align two documents for better comparison results. */ class DocumentComparisonExample(context: Context) : SdkExample(context, R.string.documentComparisonExampleTitle, R.string.documentComparisonExampleDescription) { private val documentAIndex = 0 // Destination page index private val documentBIndex = 0 // Source page index @SuppressLint("CheckResult") override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) { // We'll show progress dialog while processing documents with PdfProcessor. val progressDialog = createProgressDialog(context) progressDialog.show() configuration.apply { // The example uses a custom activity with a floating action button to start document alignment. layout(R.layout.activity_document_comparison) // Disable features that are not important for this example. setThumbnailBarMode(ThumbnailBarMode.THUMBNAIL_BAR_MODE_NONE) annotationEditingEnabled(false) outlineEnabled(false) settingsMenuEnabled(false) bookmarkListEnabled(false) thumbnailGridEnabled(false) annotationListEnabled(false) documentInfoViewEnabled(false) searchEnabled(false) printingEnabled(false) contentEditingEnabled(false) setEnabledShareFeatures(EnumSet.noneOf(ShareFeatures::class.java)) invertColors(false) } // Comparison process consists from 2 steps: // 1. Color strokes from both documents in different colors. // 2. Merge 2 pages from these documents with colored strokes together. val processDocumentsForComparison = Single.defer { // Color strokes in the old document to GREEN. val greenDocumentUri = changeStrokeColorForDocumentFromAssets( context, "comparison/Document-A.pdf", oldDocumentColor, "Document-A", documentAIndex, ) // Color strokes in the new document to RED. val redDocumentUri = changeStrokeColorForDocumentFromAssets( context, "comparison/Document-B.pdf", newDocumentColor, "Document-B", documentBIndex, ) // Now generate document by merging both colored pages. val mergedDocumentUri = generateComparisonDocument(context, greenDocumentUri, redDocumentUri, "Comparison") // Return Single emitting triple of red, green and merged documents. return@defer Single.just(Triple(greenDocumentUri, redDocumentUri, mergedDocumentUri)) } processDocumentsForComparison.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).doFinally { // Hide the progress dialog when processing finishes. progressDialog.hide() }.subscribe( Consumer { // Start the PdfActivity with all 3 documents loaded in tabs. This will show documents A and B, as well as the // comparison result. val documentTabs = arrayOf( DocumentDescriptor.fromUri(it.first), DocumentDescriptor.fromUri(it.second), DocumentDescriptor.fromUri(it.third).apply { setTitle("Comparison") }, ) val intent = PdfActivityIntentBuilder.fromDocumentDescriptor(context, *documentTabs).configuration(configuration.build()) // Make the tab with comparison document visible after starting the activity..visibleDocument(2).activityClass(DocumentComparisonActivity::class.java).build() context.startActivity(intent) }, ) } private fun changeStrokeColorForDocumentFromAssets( context: Context, documentAsset: String, color: Int, outputFileName: String, pageIndex: Int, ): Uri { val outputFile = File(context.filesDir, "$outputFileName.pdf") val sourceDocument = PdfDocumentLoader.openDocument(context, DocumentSource(AssetDataProvider(documentAsset))) val task = PdfProcessorTask.fromDocument(sourceDocument).changeStrokeColorOnPage(pageIndex, color) PdfProcessor.processDocument(task, outputFile) return Uri.fromFile(outputFile) } private fun generateComparisonDocument(context: Context, oldDocumentUri: Uri, newDocumentUri: Uri, outputFileName: String): Uri { val outputFile = File(context.filesDir, "$outputFileName.pdf") val oldDocument = PdfDocumentLoader.openDocument(context, oldDocumentUri) val task = PdfProcessorTask.fromDocument(oldDocument).mergePage(PagePdf(context, newDocumentUri, documentBIndex), documentAIndex, BlendMode.DARKEN) PdfProcessor.processDocument(task, outputFile) return Uri.fromFile(outputFile) } private fun createProgressDialog(context: Context): ProgressDialog { val progressDialog = ProgressDialog(context) progressDialog.setTitle("Comparing documents") progressDialog.setProgressNumberFormat(null) progressDialog.setProgressPercentFormat(null) progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL) progressDialog.isIndeterminate = true progressDialog.setCancelable(false) return progressDialog } companion object { /** Tint color used for the old document. */ val oldDocumentColor = "#F5281B".toColorInt() /** Tint color used for the new document. */ val newDocumentColor = "#31C1FF".toColorInt() } } /** * This activity displays two documents to compare and the merged document. * It receives the selected points to updates the aligned comparison document. */ class DocumentComparisonActivity : PdfActivity(), ComparisonDialogListener { private lateinit var oldDocumentSource: DocumentSource private lateinit var newDocumentSource: DocumentSource override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) if (documentCoordinator.documents.size!= 3) { error("This example is built to be launched with exactly 3 documents only (document A, B, and comparison result).") } // This example assumes that the first two documents are the original documents A and B. oldDocumentSource = documentCoordinator.documents[0].documentSource newDocumentSource = documentCoordinator.documents[1].documentSource initViews() if (savedInstanceState!= null) { // If this activity is recreated after a configuration change, calling restore() ensures that the document will have the // correct callback (this activity) if it was shown before the configuration change. If no dialog was shown, this call is a // no-op. DocumentComparisonDialog.restore(this, this) } } private fun initViews() { pspdfKitViews.tabBar?.apply { setCloseMode(PdfTabBarCloseMode.CLOSE_DISABLED) // Center the tabs. gravity = Gravity.CENTER_HORIZONTAL } val alignDocumentsButton = findViewById(R.id.pspdf_fab_align) // Make sure the floating action button is not hidden behind the navigation bar (neither in normal mode nor in immersive mode). alignDocumentsButton.setOnApplyWindowInsetsListener { _, insets -> alignDocumentsButton.layoutParams = (alignDocumentsButton.layoutParams as RelativeLayout.LayoutParams).apply { val margin = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 16f, resources.displayMetrics).toInt() bottomMargin = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) { margin + insets.getInsets(WindowInsets.Type.systemBars()).bottom } else { @Suppress("DEPRECATION") margin + insets.systemWindowInsetBottom } } insets } alignDocumentsButton.setOnClickListener { val outputFile = filesDir.resolve("comparison-result.pdf") val oldDocument = ComparisonDocument(oldDocumentSource, 0, DocumentComparisonExample.oldDocumentColor) val newDocument = ComparisonDocument(newDocumentSource, 0, DocumentComparisonExample.newDocumentColor) DocumentComparisonDialog.show(this, configuration, oldDocument, newDocument, outputFile, this) } } override fun onSetActivityTitle(configuration: PdfActivityConfiguration, document: PdfDocument?) { super.onSetActivityTitle(configuration, document) supportActionBar?.title = "Compare Documents" } override fun onComparisonSuccessful(alignedDocument: DocumentSource) { // Amit note: not sure if this code needs to handle non-file sources, but it doesn't, so return if not. val fileUri = alignedDocument.fileUri?: return // Try to replace comparison document. try { documentCoordinator.removeDocument(documentCoordinator.documents[2]) documentCoordinator.addDocument(DocumentDescriptor.fromUri(fileUri), 2) documentCoordinator.documents[2].setTitle("Comparison") documentCoordinator.setVisibleDocument(documentCoordinator.documents[2]) } catch (e: IndexOutOfBoundsException) { e.printStackTrace() } } override fun onError(error: Throwable) { Log.e("Example", "An error happened while comparing the documents.", error) Toast.makeText(this, "There was a comparison error. Check logcat for details.", Toast.LENGTH_LONG).show() } } ``` This code sample is an example that illustrates how to use our SDK. Please adapt it to your specific use case. --- ## Related pages - [Application Policy](/guides/android/samples/application-policy-kotlin.md) - [Custom Form Highlight Color](/guides/android/samples/custom-form-highlight-color-java.md) - [Custom Page Templates](/guides/android/samples/custom-page-templates-java.md) - [Digital Signature (Basic)](/guides/android/samples/digital-signature-basic-kotlin.md) - [Disabled Annotation Property](/guides/android/samples/disabled-annotation-property-java.md) - [Image Document](/guides/android/samples/image-document-kotlin.md) - [Compose Image Document](/guides/android/samples/compose-image-document-kotlin.md) - [Inline Multimedia](/guides/android/samples/inline-multimedia-kotlin.md) - [JavaScript Form Filling](/guides/android/samples/javascript-form-filling-kotlin.md) - [Overlay Visibility](/guides/android/samples/overlay-visibility-kotlin.md) - [PdfFragment](/guides/android/samples/pdffragment-kotlin.md) - [Reader View](/guides/android/samples/reader-view-kotlin.md) - 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