HomeScreen: list of recent documents

app/build.gradle.kts

@@ -3,6 +3,7 @@ plugins {
     alias(libs.plugins.kotlin.android)
     alias(libs.plugins.kotlin.compose)
     alias(libs.plugins.aboutLibraries)
+    alias(libs.plugins.protobuf)
 }
 
 android {
@@ -85,6 +86,8 @@ dependencies {
     implementation(libs.androidx.camera.camera2)
     implementation(libs.androidx.camera.lifecycle)
     implementation(libs.androidx.camera.view)
+    implementation(libs.androidx.datastore)
+    implementation(libs.protobuf.javalite)
     implementation(libs.litert)
     implementation(libs.litert.support)
     implementation(libs.litert.metadata)
@@ -107,3 +110,19 @@ dependencies {
 aboutLibraries {
     android.registerAndroidTasks = true
 }
+
+protobuf {
+    protoc {
+        artifact = "com.google.protobuf:protoc:4.32.0"
+    }
+    generateProtoTasks {
+        all().forEach { task ->
+            task.builtins {
+                create("java") {
+                    option("lite")
+                }
+            }
+        }
+    }
+}
+

app/src/main/java/org/mydomain/myscan/MainActivity.kt

@@ -29,6 +29,7 @@ import androidx.activity.viewModels
 import androidx.compose.runtime.getValue
 import androidx.core.content.FileProvider
 import androidx.core.net.toFile
+import androidx.core.net.toUri
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.lifecycleScope
 import kotlinx.coroutines.CoroutineScope
@@ -72,11 +73,14 @@ class MainActivity : ComponentActivity() {
                 )
                 when (val screen = currentScreen) {
                     is Screen.Home -> {
+                        val recentDocs by viewModel.recentDocuments.collectAsStateWithLifecycle()
                         HomeScreen(
                             cameraPermission = cameraPermission,
                             currentDocument = document,
                             navigation = navigation,
                             onStartNewScan = navigation.toCameraScreen,
+                            recentDocuments = recentDocs,
+                            onOpenPdf = { file -> openPdf(file.toUri()) }
                         )
                     }
                     is Screen.Camera -> {
@@ -149,6 +153,7 @@ class MainActivity : ComponentActivity() {
         appScope.launch {
             try {
                 val targetFile = viewModel.saveFile(generatedPdf.file)
+                viewModel.addRecentDocument(targetFile.absolutePath, generatedPdf.pageCount)
 
                 suspendCancellableCoroutine { continuation ->
                     MediaScannerConnection.scanFile(

app/src/main/java/org/mydomain/myscan/MainViewModel.kt

@@ -21,6 +21,7 @@ import android.os.Environment
 import android.util.Log
 import androidx.camera.core.ImageProxy
 import androidx.core.net.toUri
+import androidx.datastore.core.DataStore
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.viewModelScope
@@ -37,7 +38,9 @@ import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
+import org.mydomain.myscan.data.recentDocumentsDataStore
 import org.mydomain.myscan.ui.PdfGenerationUiState
+import org.mydomain.myscan.ui.RecentDocumentUiState
 import org.mydomain.myscan.view.DocumentUiModel
 import java.io.ByteArrayOutputStream
 import java.io.File
@@ -46,6 +49,7 @@ class MainViewModel(
     private val imageSegmentationService: ImageSegmentationService,
     private val imageRepository: ImageRepository,
     private val pdfFileManager: PdfFileManager,
+    private val recentDocumentsDataStore: DataStore<RecentDocuments>,
 ): ViewModel() {
 
     companion object {
@@ -59,6 +63,7 @@ class MainViewModel(
                         File(context.cacheDir, "pdfs"),
                         Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
                         AndroidPdfWriter()),
+                    context.recentDocumentsDataStore,
                 ) as T
             }
         }
@@ -314,6 +319,42 @@ class MainViewModel(
     fun cleanUpOldPdfs(thresholdInMillis: Int) {
         pdfFileManager.cleanUpOldFiles(thresholdInMillis)
     }
+
+
+    val recentDocuments: StateFlow<List<RecentDocumentUiState>> =
+        recentDocumentsDataStore.data.map {
+            it.documentsList.map {
+                doc ->
+                    RecentDocumentUiState(
+                        file = File(doc.filePath),
+                        saveTimestamp = doc.createdAt,
+                        pageCount = doc.pageCount,
+                    )
+            }.filter { doc -> doc.file.exists() }
+        }.stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5_000),
+            initialValue = emptyList(),
+        )
+    fun addRecentDocument(filePath: String, pageCount: Int) {
+        viewModelScope.launch {
+            recentDocumentsDataStore.updateData { current ->
+                val newDoc = RecentDocument.newBuilder()
+                    .setFilePath(filePath)
+                    .setPageCount(pageCount)
+                    .setCreatedAt(System.currentTimeMillis())
+                    .build()
+                current.toBuilder()
+                    .addDocuments(0, newDoc)
+                    .also { builder ->
+                        while (builder.documentsCount > 10) {
+                            builder.removeDocuments(builder.documentsCount - 1)
+                        }
+                    }
+                    .build()
+            }
+        }
+    }
 }
 
 data class GeneratedPdf(

app/src/main/java/org/mydomain/myscan/data/RecentDocuments.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2025 Pierre-Yves Nicolas
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option)
+ * any later version.
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.mydomain.myscan.data
+
+import android.content.Context
+import androidx.datastore.core.CorruptionException
+import androidx.datastore.core.DataStore
+import androidx.datastore.core.Serializer
+import androidx.datastore.dataStore
+import com.google.protobuf.InvalidProtocolBufferException
+import org.mydomain.myscan.RecentDocuments
+import java.io.InputStream
+import java.io.OutputStream
+
+object RecentDocumentsSerializer : Serializer<RecentDocuments> {
+    override val defaultValue: RecentDocuments = RecentDocuments.getDefaultInstance()
+
+    override suspend fun readFrom(input: InputStream): RecentDocuments {
+        return try {
+            RecentDocuments.parseFrom(input)
+        } catch (e: InvalidProtocolBufferException) {
+            throw CorruptionException("Cannot read proto.", e)
+        }
+    }
+
+    override suspend fun writeTo(
+        t: RecentDocuments,
+        output: OutputStream
+    ) = t.writeTo(output)
+}
+
+val Context.recentDocumentsDataStore: DataStore<RecentDocuments> by dataStore(
+    fileName = "recent_documents.pb",
+    serializer = RecentDocumentsSerializer
+)

app/src/main/java/org/mydomain/myscan/ui/UiState.kt

@@ -16,6 +16,7 @@ package org.mydomain.myscan.ui
 
 import android.net.Uri
 import org.mydomain.myscan.GeneratedPdf
+import java.io.File
 
 data class PdfGenerationUiState(
     val isGenerating: Boolean = false,
@@ -25,3 +26,9 @@ data class PdfGenerationUiState(
     val saveDirectoryName: String? = null,
     val errorMessage: String? = null
 )
+
+data class RecentDocumentUiState(
+    val file: File,
+    val saveTimestamp: Long,
+    val pageCount: Int,
+)

app/src/main/java/org/mydomain/myscan/view/HomeScreen.kt

@@ -15,6 +15,7 @@
 package org.mydomain.myscan.view
 
 import androidx.compose.foundation.Image
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
@@ -27,10 +28,14 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.PhotoCamera
+import androidx.compose.material.icons.filled.PictureAsPdf
 import androidx.compose.material3.BottomAppBar
 import androidx.compose.material3.Button
 import androidx.compose.material3.Card
 import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.ListItem
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Text
@@ -49,7 +54,10 @@ import org.mydomain.myscan.CameraPermissionState
 import org.mydomain.myscan.Navigation
 import org.mydomain.myscan.R
 import org.mydomain.myscan.rememberCameraPermissionState
+import org.mydomain.myscan.ui.RecentDocumentUiState
 import org.mydomain.myscan.ui.theme.MyScanTheme
+import java.io.File
+import kotlin.math.min
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -57,7 +65,9 @@ fun HomeScreen(
     cameraPermission: CameraPermissionState,
     currentDocument: DocumentUiModel,
     navigation: Navigation,
-    onStartNewScan: () -> Unit
+    onStartNewScan: () -> Unit,
+    recentDocuments: List<RecentDocumentUiState>,
+    onOpenPdf: (File) -> Unit,
 ) {
     val showCloseDocDialog = rememberSaveable { mutableStateOf(false) }
     Scaffold (
@@ -104,6 +114,11 @@ fun HomeScreen(
                 CurrentDocumentCard(currentDocument, navigation)
             }
 
+            if (recentDocuments.isNotEmpty()) {
+                SectionTitle(stringResource(R.string.last_saved_documents))
+                RecentDocumentList(recentDocuments, onOpenPdf)
+            }
+
             if (showCloseDocDialog.value) {
                 NewDocumentDialog(
                     onConfirm = onStartNewScan,
@@ -166,6 +181,32 @@ private fun CurrentDocumentCard(
     }
 }
 
+@Composable
+private fun RecentDocumentList(
+    recentDocuments: List<RecentDocumentUiState>,
+    onOpenPdf: (File) -> Unit
+) {
+    Column {
+        val maxListSize = 5
+        recentDocuments.subList(0, min(maxListSize, recentDocuments.size)).forEach { doc ->
+            ListItem(
+                headlineContent = { Text(doc.file.name) },
+                supportingContent = {
+                    Text(
+                        text = pageCountText(doc.pageCount) + " • " +
+                                formatDate(doc.saveTimestamp, LocalContext.current)
+                    )
+                },
+                leadingContent = {
+                    Icon(Icons.Default.PictureAsPdf, contentDescription = null)
+                },
+                modifier = Modifier.clickable { onOpenPdf(doc.file) }
+            )
+            HorizontalDivider()
+        }
+    }
+}
+
 @Composable
 private fun SectionTitle(text: String) {
     Text(
@@ -183,7 +224,9 @@ fun HomeScreenPreviewOnFirstLaunch() {
             cameraPermission = rememberCameraPermissionState(),
             currentDocument = DocumentUiModel(listOf()) { _ -> null },
             navigation = dummyNavigation(),
-            onStartNewScan = {}
+            onStartNewScan = {},
+            recentDocuments = listOf(),
+            onOpenPdf = {},
         )
     }
 }
@@ -198,7 +241,12 @@ fun HomeScreenPreviewWithCurrentDocument() {
                 listOf("gallica.bnf.fr-bpt6k5530456s-1.jpg"),
                 LocalContext.current),
             navigation = dummyNavigation(),
-            onStartNewScan = {}
+            onStartNewScan = {},
+            recentDocuments = listOf(
+                RecentDocumentUiState(File("/path/my_file.pdf"), 1755971180000, 3),
+                RecentDocumentUiState(File("/path/scan2.pdf"), 1755000500000, 1)
+            ),
+            onOpenPdf = {},
         )
     }
 }

app/src/main/java/org/mydomain/myscan/view/Strings.kt

@@ -14,12 +14,21 @@
  */
 package org.mydomain.myscan.view
 
+import android.content.Context
+import android.text.format.DateFormat
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.platform.LocalContext
 import org.mydomain.myscan.R
+import java.util.Date
 
 @Composable
 fun pageCountText(quantity: Int): String {
     val context = LocalContext.current
     return context.resources.getQuantityString(R.plurals.page_count, quantity, quantity)
 }
+
+fun formatDate(timestamp: Long, context: Context): String {
+    val date = Date(timestamp)
+    return DateFormat.getMediumDateFormat(context).format(date) + " " +
+            DateFormat.getTimeFormat(context).format(date)
+}

app/src/main/proto/recent_documents.proto

@@ -0,0 +1,14 @@
+syntax = "proto3";
+
+option java_package = "org.mydomain.myscan";
+option java_multiple_files = true;
+
+message RecentDocument {
+  string file_path = 1;
+  int64 created_at = 2; // timestamp in ms
+  int32 page_count = 3;
+}
+
+message RecentDocuments {
+  repeated RecentDocument documents = 1;
+}

app/src/main/res/values-fr/strings.xml

@@ -19,6 +19,7 @@
     <string name="export_pdf">Exporter en PDF</string>
     <string name="filename">Nom de fichier</string>
     <string name="grant_permission">Autoriser</string>
+    <string name="last_saved_documents">Derniers documents enregistrés</string>
     <string name="libraries">Bibliothèques</string>
     <string name="libraries_intro">Cette application utilise plusieurs bibliothèques open source, notamment :</string>
     <string name="libraries_open_source">Bibliothèques open source</string>

app/src/main/res/values/strings.xml

@@ -19,6 +19,7 @@
     <string name="export_pdf">Export PDF</string>
     <string name="filename">Filename</string>
     <string name="grant_permission">Grant permission</string>
+    <string name="last_saved_documents">Last saved documents</string>
     <string name="libraries">Libraries</string>
     <string name="libraries_intro">This application uses several open-source libraries, including:</string>
     <string name="libraries_open_source">Open-source libraries</string>

gradle/libs.versions.toml

@@ -10,12 +10,15 @@ lifecycleRuntimeKtx = "2.9.1"
 activityCompose = "1.10.1"
 composeBom = "2025.06.01"
 camerax = "1.4.2"
+datastore = "1.1.7"
 litert = "1.4.0"
 opencv = "4.12.0"
 assertj = "3.27.3"
 pdfbox = "2.0.27.0"
 zoomable = "2.8.1"
 aboutLibraries = "12.2.4"
+protobuf = "0.9.5"
+protobufJavaLite = "4.32.0"
 
 [libraries]
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
@@ -40,6 +43,8 @@ androidx-camera-core = { group = "androidx.camera", name = "camera-core", versio
 androidx-camera-camera2 = { group = "androidx.camera", name = "camera-camera2", version.ref = "camerax" }
 androidx-camera-lifecycle = { group = "androidx.camera", name = "camera-lifecycle", version.ref = "camerax" }
 androidx-camera-view = { group = "androidx.camera", name = "camera-view", version.ref = "camerax" }
+androidx-datastore = { group = "androidx.datastore", name = "datastore" , version.ref = "datastore" }
+protobuf-javalite = { group = "com.google.protobuf", name="protobuf-javalite", version.ref = "protobufJavaLite"}
 litert = { group = "com.google.ai.edge.litert", name = "litert", version.ref = "litert" }
 litert-support = { group = "com.google.ai.edge.litert", name = "litert-support", version.ref = "litert" }
 litert-metadata = { group = "com.google.ai.edge.litert", name = "litert-metadata", version.ref = "litert" }
@@ -56,4 +61,5 @@ kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
 kotlin-compose = { id = "org.jetbrains.kotlin.plugin.compose", version.ref = "kotlin" }
 license =  { id = "com.github.hierynomus.license", version.ref = "license" }
 aboutLibraries = { id = "com.mikepenz.aboutlibraries.plugin", version.ref = "aboutLibraries" }
+protobuf = { id = "com.google.protobuf", version.ref = "protobuf" }