Customize PDF download progress 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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package com.pspdfkit.catalog.examples.kotlin
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import android.content.Context
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import android.os.Parcel
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import android.os.Parcelable
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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.utils.StringUtils
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import com.pspdfkit.configuration.activity.PdfActivityConfiguration
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import com.pspdfkit.document.download.DownloadJob
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import com.pspdfkit.document.download.DownloadRequest
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import com.pspdfkit.document.download.Progress
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import com.pspdfkit.document.providers.DataProvider
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import com.pspdfkit.document.providers.InputStreamDataProvider
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import com.pspdfkit.document.providers.ProgressDataProvider
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import com.pspdfkit.ui.PdfActivity
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import com.pspdfkit.ui.PdfActivityIntentBuilder
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import io.reactivex.rxjava3.core.BackpressureStrategy
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import io.reactivex.rxjava3.core.Flowable
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import io.reactivex.rxjava3.subjects.PublishSubject
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import java.io.File
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import java.io.FileInputStream
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import java.io.InputStream
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import java.util.concurrent.CountDownLatch
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/**
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 * This example shows how to create a custom data provider that loads a document from the web and
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 * shows the progress in the [PdfActivity]. Furthermore, it implements [Parcelable] to allow using
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 * the data provider with [PdfActivity].
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 */
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class ProgressProviderExample(context: Context) : SdkExample(context, R.string.progressProviderExampleTitle, R.string.progressProviderExampleDescription) {
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    override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) {
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        // Create an instance of the custom data provider. See the implementation details below.
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        val dataProvider: DataProvider = RemoteDataProvider("https://nutrient.io/downloads/case-study-box.pdf")
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        // Start the activity using our custom data provider.
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        val intent = PdfActivityIntentBuilder.fromDataProvider(context, dataProvider)
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            .configuration(configuration.build())
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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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 * Custom data provider for loading a PDF document from the web. This provider derives from
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 * [InputStreamDataProvider] which handles loading data from a stream object.
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 *
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 * @param url The url of the PDF document.
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 */
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private class RemoteDataProvider(
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    /** The url where the PDF document is located.  */
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    private val url: String
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) : InputStreamDataProvider(), ProgressDataProvider, Parcelable {
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    /** Responsible for downloading our PDF.  */
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    private var downloadJob: DownloadJob? = null
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    /** Used to wait until the download is done.  */
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    private val downloadLatch = CountDownLatch(1)
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    /** Used to notify the PdfFragment of download progress updates.  */
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    private val progressSubject = PublishSubject.create<Double>()
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    override fun observeProgress(): Flowable<Double> { // We can just return our PublishSubject.
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        return progressSubject.toFlowable(BackpressureStrategy.LATEST)
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    }
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    @Throws(Exception::class)
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    override fun openInputStream(): InputStream {
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        val downloadJob = startDownloadIfNotRunning()
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        // We need to wait until our download is finished.
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        downloadLatch.await()
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        return FileInputStream(downloadJob.outputFile)
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    }
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    override fun getSize(): Long {
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        val downloadJob = startDownloadIfNotRunning()
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        // We need to wait until our download is finished.
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        try {
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            downloadLatch.await()
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        } catch (ex: InterruptedException) {
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            return DataProvider.FILE_SIZE_UNKNOWN.toLong()
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        }
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        return downloadJob.outputFile.length()
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    }
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    override fun getUid(): String {
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        return StringUtils.sha1(url)
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    }
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    override fun getTitle(): String? {
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        return url
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    }
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    /**
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     * Starts our download if it wasn't already started.
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     */
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    private fun startDownloadIfNotRunning(): DownloadJob {
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        var downloadJob = this.downloadJob
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        if (downloadJob == null) {
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            try {
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                // We delay starting the download so the progress bar will appear,
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                // this is only required because our example file is so small.
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                Thread.sleep(2000)
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            } catch (ignored: InterruptedException) {
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            }
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            downloadJob = DownloadJob.startDownload(
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                DownloadRequest.Builder(getContext())
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                    .uri(url)
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                    .outputFile(File(getContext().getDir("documents", Context.MODE_PRIVATE), "temp.pdf"))
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                    .overwriteExisting(true)
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                    .build()
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            )
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            downloadJob.setProgressListener(object : DownloadJob.ProgressListener {
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                override fun onProgress(progress: Progress) {
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                    // Notify our listeners about the download progress.
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                    progressSubject.onNext(progress.bytesReceived.toDouble() / progress.totalBytes.toDouble())
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                }
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                override fun onComplete(output: File) {
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                    progressSubject.onComplete()
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                    downloadLatch.countDown()
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                }
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                override fun onError(exception: Throwable) {
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                    progressSubject.onError(exception)
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                    downloadLatch.countDown()
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                }
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            })
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        }
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        this.downloadJob = downloadJob
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        return downloadJob as DownloadJob
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    }
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    override fun describeContents(): Int {
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        return 0
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    }
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    override fun writeToParcel(dest: Parcel, flags: Int) {
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        dest.writeString(url)
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    }
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    private constructor(input: Parcel) : this(input.readString()!!)
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    companion object CREATOR : Parcelable.Creator<RemoteDataProvider> {
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        override fun createFromParcel(parcel: Parcel): RemoteDataProvider {
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            return RemoteDataProvider(parcel)
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        }
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        override fun newArray(size: Int): Array<RemoteDataProvider?> {
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            return arrayOfNulls(size)
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        }
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    }
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}