Request storage permission to save PDF on Android <= 9

Author: pynicolas

.gitignore

@@ -8,6 +8,8 @@
 /.idea/navEditor.xml
 /.idea/assetWizardSettings.xml
 /.idea/androidTestResultsUserPreferences.xml
+/.idea/deviceManager.xml
+/.idea/deploymentTargetSelector.xml
 .DS_Store
 /build
 /captures

app/src/main/AndroidManifest.xml

@@ -7,7 +7,7 @@
         android:required="false" />
     <uses-permission android:name="android.permission.CAMERA" />
     <!-- Required (on Android 9 and lower) to save files -->
-    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
+    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="28"/>
 
     <application
         android:allowBackup="true"

app/src/main/java/org/fairscan/app/MainActivity.kt

@@ -14,19 +14,28 @@
  */
 package org.fairscan.app
 
+import android.Manifest
 import android.content.ActivityNotFoundException
 import android.content.Intent
 import android.content.pm.PackageManager
+import android.content.pm.PackageManager.PERMISSION_GRANTED
 import android.media.MediaScannerConnection
 import android.net.Uri
+import android.os.Build.VERSION.SDK_INT
+import android.os.Build.VERSION_CODES.Q
 import android.os.Bundle
 import android.util.Log
 import android.widget.Toast
 import androidx.activity.ComponentActivity
+import androidx.activity.compose.ManagedActivityResultLauncher
+import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.activity.viewModels
 import androidx.compose.runtime.getValue
+import androidx.compose.ui.platform.LocalContext
+import androidx.core.content.ContextCompat.checkSelfPermission
 import androidx.core.content.FileProvider
 import androidx.core.net.toFile
 import androidx.core.net.toUri
@@ -59,10 +68,22 @@ class MainActivity : ComponentActivity() {
         }
         enableEdgeToEdge()
         setContent {
+            val context = LocalContext.current
             val currentScreen by viewModel.currentScreen.collectAsStateWithLifecycle()
             val liveAnalysisState by viewModel.liveAnalysisState.collectAsStateWithLifecycle()
             val document by viewModel.documentUiModel.collectAsStateWithLifecycle()
             val cameraPermission = rememberCameraPermissionState()
+            val savePdf = { savePdf(viewModel.getFinalPdf(), viewModel) }
+            val storagePermissionLauncher = rememberLauncherForActivityResult(
+                ActivityResultContracts.RequestPermission()
+            ) { isGranted ->
+                if (isGranted) {
+                    savePdf()
+                } else {
+                    val message = getString(R.string.storage_permission_denied)
+                    Toast.makeText(context, message, Toast.LENGTH_SHORT).show()
+                }
+            }
             MyScanTheme {
                 val navigation = Navigation(
                     toHomeScreen = { viewModel.navigateTo(Screen.Main.Home) },
@@ -112,7 +133,7 @@ class MainActivity : ComponentActivity() {
                                 setFilename = viewModel::setFilename,
                                 uiStateFlow = viewModel.pdfUiState,
                                 sharePdf = { sharePdf(viewModel.getFinalPdf(), viewModel) },
-                                savePdf = { savePdf(viewModel.getFinalPdf(), viewModel) },
+                                savePdf = { checkPermissionThen(storagePermissionLauncher, savePdf) },
                                 openPdf = { openPdf(viewModel.pdfUiState.value.savedFileUri) }
                             ),
                             onCloseScan = {
@@ -154,6 +175,19 @@ class MainActivity : ComponentActivity() {
         startActivity(chooser)
     }
 
+    private fun checkPermissionThen(
+        requestPermissionLauncher: ManagedActivityResultLauncher<String, Boolean>,
+        action: () -> Unit
+    ) {
+        val permission = Manifest.permission.WRITE_EXTERNAL_STORAGE
+        if (SDK_INT < Q && checkSelfPermission(this, permission) != PERMISSION_GRANTED
+        ) {
+            requestPermissionLauncher.launch(permission)
+        } else {
+            action()
+        }
+    }
+
     private fun savePdf(generatedPdf: GeneratedPdf?, viewModel: MainViewModel) {
         if (generatedPdf == null)
             return

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

@@ -41,6 +41,7 @@
     <string name="scan_in_progress">Scan läuft</string>
     <string name="share">Teilen</string>
     <string name="share_pdf">PDF teilen</string>
+    <string name="storage_permission_denied">PDF-Datei kann nicht gespeichert werden: Berechtigung verweigert</string>
     <string name="unknown_size">Unbekannte Größe</string>
     <string name="version">Version</string>
     <string name="view_the_full_license">Vollständige Lizenz anzeigen</string>

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

@@ -41,6 +41,7 @@
     <string name="scan_in_progress">Scan en cours</string>
     <string name="share">Partager</string>
     <string name="share_pdf">Partager le PDF</string>
+    <string name="storage_permission_denied">Impossible d’enregistrer le fichier PDF : permission refusée</string>
     <string name="unknown_size">Taille inconnue</string>
     <string name="version">Version</string>
     <string name="view_the_full_license">Voir la licence complète</string>

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

@@ -42,6 +42,7 @@
     <string name="scan_in_progress">Scan in progress</string>
     <string name="share">Share</string>
     <string name="share_pdf">Share PDF</string>
+    <string name="storage_permission_denied">Cannot save PDF file: permission was denied</string>
     <string name="unknown_size">Unknown size</string>
     <string name="version">Version</string>
     <string name="view_the_full_license">View the full license</string>