Add LTV to Existing Signature

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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.content.Context
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import android.net.Uri
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import android.view.Menu
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import android.view.MenuItem
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import android.widget.Toast
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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.tasks.ExtractAssetTask
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import com.pspdfkit.configuration.activity.PdfActivityConfiguration
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import com.pspdfkit.forms.SignatureFormElement
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import com.pspdfkit.signatures.SignerOptions
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import com.pspdfkit.signatures.SigningManager
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import com.pspdfkit.signatures.TrustedKeyStore
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import com.pspdfkit.signatures.loadCertificateFromStream
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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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import io.reactivex.rxjava3.disposables.Disposable
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import io.reactivex.rxjava3.schedulers.Schedulers
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import java.security.cert.X509Certificate
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/**
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 * An example that shows how to digitally sign a PDF document using [SigningManager].
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 * This is a Simple implementation where user provides Private key in [SignerOptions].
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 */
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class LongTermValidationAfterSigningExample(context: Context) :
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    SdkExample(context, R.string.digitalSignatureLtvAddedExampleTitle, R.string.digitalSignatureLtvAddedExampleDescription) {
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    override fun launchExample(context: Context, configuration: PdfActivityConfiguration.Builder) {
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        ExtractAssetTask.extract("SignedWithoutLtv.pdf", title, context) { documentFile ->
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            val intent =
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                PdfActivityIntentBuilder
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                    .fromUri(context, Uri.fromFile(documentFile))
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                    .configuration(configuration.build())
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                    .activityClass(AddLtvAfterSigningActivity::class)
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                    .build()
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            // Start the MeasurementToolsActivity for the extracted document.
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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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 * An implementation that provides a button to add long term validation info to a signed document.
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 */
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class AddLtvAfterSigningActivity : PdfActivity() {
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    private var addLtvDisposable: Disposable? = null
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    private fun addLtv() {
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        val handleError: (Throwable) -> Unit = {
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            Toast.makeText(this, "Error adding LTV! See log.", Toast.LENGTH_SHORT).show()
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            PdfLog.e("AddLtvAfterSigningActivity", it.message, "Error adding LTV.")
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        }
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        try {
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            val document = document ?: throw IllegalStateException("Document not found.")
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            val signatureForm =
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                document.formProvider.getFormElementWithName("Signature") as? SignatureFormElement
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                    ?: throw IllegalStateException("Signature form element not found.")
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            val trustedCertificates = getTrustedCertificates()
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            TrustedKeyStore.clearTrustedCertificates()
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            TrustedKeyStore.addTrustedCertificates(trustedCertificates)
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            addLtvDisposable?.dispose()
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            // We can choose not to pass certificates here and the ones in the document's signature will be fetched instead.
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            addLtvDisposable =
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                document
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                    .addLongTermValidation(signatureForm, listOf())
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                    .subscribeOn(Schedulers.io())
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                    .observeOn(AndroidSchedulers.mainThread())
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                    .subscribe(
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                        {
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                            Toast.makeText(this, "LTV data added to signature!", Toast.LENGTH_SHORT).show()
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                        },
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                    ) { throwable ->
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                        handleError(throwable)
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                    }
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        } catch (e: Exception) {
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            handleError(e)
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        }
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    }
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    override fun onCreateOptionsMenu(menu: Menu): Boolean {
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        super.onCreateOptionsMenu(menu)
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        menu.add(0, ADD_LTV_ID, 0, "Add LTV")
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        return true
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    }
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    override fun onOptionsItemSelected(item: MenuItem): Boolean = if (item.itemId == ADD_LTV_ID) {
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        addLtv()
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        true
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    } else {
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        super.onOptionsItemSelected(item)
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    }
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    private fun getTrustedCertificates(): List<X509Certificate> = listOf(
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        loadCertificateFromStream(assets.open("digital-signatures/ltv/Root.cert")),
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        loadCertificateFromStream(assets.open("digital-signatures/ltv/Issuer.cert")),
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    )
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    companion object {
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        private const val ADD_LTV_ID = 1
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    }
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}