Add a page during scroll

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/*
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 *   Copyright © 2020-2026 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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package com.pspdfkit.catalog.examples.kotlin
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import android.annotation.SuppressLint
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import android.content.Context
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import android.graphics.Color
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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.catalog.SdkExample.Companion.TAG
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import com.pspdfkit.catalog.tasks.ExtractAssetTask
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import com.pspdfkit.configuration.activity.PdfActivityConfiguration
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import com.pspdfkit.configuration.page.PageScrollDirection
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import com.pspdfkit.configuration.page.PageScrollMode
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import com.pspdfkit.document.PdfDocument
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import com.pspdfkit.document.editor.PdfDocumentEditorFactory
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import com.pspdfkit.document.processor.NewPage
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import com.pspdfkit.document.processor.PagePattern
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import com.pspdfkit.listeners.scrolling.DocumentScrollListener
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import com.pspdfkit.listeners.scrolling.ScrollState
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import com.pspdfkit.ui.DocumentDescriptor
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import com.pspdfkit.ui.PdfActivity
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import com.pspdfkit.ui.PdfActivityIntentBuilder
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import com.pspdfkit.utils.PdfLog
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import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
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/**
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 * An example that shows how to use the onDocumentScrolled() callback to detect when the page has reached its end.
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 */
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class DocumentScrollExample(context: Context) : SdkExample(context, R.string.documentScrollExampleTitle, R.string.documentScrollExampleDescription) {
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    override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) {
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        // We use a custom utility class to extract the example document from the assets.
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        ExtractAssetTask.extract(WELCOME_DOC, title, context) { documentFile ->
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            // To start the `CustomLayoutActivity` create a launch intent using the builder.
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            val intent = PdfActivityIntentBuilder.fromUri(context, Uri.fromFile(documentFile))
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                .configuration(configuration.build())
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                .activityClass(DocumentScrollActivity::class)
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                .build()
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            context.startActivity(intent)
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        }
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    }
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}
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/**
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 * Shows how to determine whether the document has been scrolled to the end
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 */
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class DocumentScrollActivity : PdfActivity() {
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    private var currentZoom = 1f
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    private var currentScroll = 0
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    private var maxScroll = 0
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    private var extend = 0
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    private var isLastPage = false
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    override fun onDocumentZoomed(document: PdfDocument, pageIndex: Int, scaleFactor: Float) {
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        currentZoom = scaleFactor
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    }
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    override fun onPageChanged(document: PdfDocument, pageIndex: Int) {
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        isLastPage = pageIndex + 1 == document.pageCount
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    }
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    override fun onDocumentLoaded(document: PdfDocument) {
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        super.onDocumentLoaded(document)
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        val pageScrollDirection = configuration.configuration.scrollDirection
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        val scrollMode = configuration.configuration.scrollMode
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        requirePdfFragment().addDocumentScrollListener(object : DocumentScrollListener {
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            override fun onScrollStateChanged(state: ScrollState) {}
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            override fun onDocumentScrolled(currX: Int, currY: Int, maxX: Int, maxY: Int, extendX: Int, extendY: Int) {
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                val isVerticalScroll = pageScrollDirection == PageScrollDirection.VERTICAL
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                val isHorizontalScroll = pageScrollDirection == PageScrollDirection.HORIZONTAL
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                val isNoZoomOrContinuousScroll = currentZoom == 1f || scrollMode == PageScrollMode.CONTINUOUS
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                val isPerPage = scrollMode == PageScrollMode.PER_PAGE
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                if (isVerticalScroll && isNoZoomOrContinuousScroll) {
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                    currentScroll = currY
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                    maxScroll = maxY
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                    extend = extendY
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                } else if (isHorizontalScroll && isNoZoomOrContinuousScroll) {
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                    currentScroll = currX
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                    maxScroll = maxX
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                    extend = extendX
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                }
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                // Handle cases for when this is the last page and the document has been zoomed in and the user tries swiping to access the next page
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                // If you do not care about the zoom, then you can get rid of this section as well as onDocumentZoomed() and onPageChanged() above
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                if (isLastPage && isPerPage && currentZoom > 1.0f) {
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                    if (isVerticalScroll) {
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                        currentScroll = currY
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                        maxScroll = maxY
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                        extend = extendY
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                    } else {
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                        currentScroll = currX
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                        maxScroll = maxX
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                        extend = extendX
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                    }
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                }
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                val scrollRange = maxScroll - extend
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                if (currentScroll == scrollRange) {
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                    PdfLog.d(TAG, "Document end: Current scroll : $currentScroll Scroll range: $scrollRange")
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                    addNewPageToDocument(document)
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                }
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            }
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        })
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    }
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    @SuppressLint("CheckResult")
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    private fun addNewPageToDocument(document: PdfDocument) {
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        val editor = PdfDocumentEditorFactory.createForDocument(document)
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        val newPage = NewPage.patternPage(NewPage.PAGE_SIZE_A5, PagePattern.LINES_7MM)
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            .backgroundColor(Color.rgb(241, 236, 121))
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            .build()
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        // Add a new page at the end of the document
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        editor.addPage(document.pageCount, newPage).blockingSubscribe()
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        // Save the document and set it
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        editor
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            .saveDocument(this, null)
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            .observeOn(AndroidSchedulers.mainThread())
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            .subscribe(
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                {
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                    val documentDescriptor = DocumentDescriptor.fromDocumentSource(document.documentSource)
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                    documentCoordinator.setDocument(documentDescriptor)
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                },
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                { e ->
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                    PdfLog.e(TAG, e, "Document couldn't be saved.")
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                }
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            )
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    }
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    companion object {
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    }
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}