Fall back to internal storage...

if external private storage is unavailable

app/src/main/java/org/tasks/preferences/Preferences.kt

@@ -378,7 +378,7 @@ class Preferences @JvmOverloads constructor(
     val backupDirectory: Uri?
         get() = getDirectory(R.string.p_backup_dir, "backups")
 
-    val externalStorage: Uri
+    val appPrivateStorage: Uri
         get() = root.uri
 
     val attachmentsDirectory: Uri?
@@ -412,13 +412,12 @@ class Preferences @JvmOverloads constructor(
                     ?: getDefaultFileLocation(name)?.let { Uri.fromFile(it) }
 
     private val root: DocumentFile
-        get() = DocumentFile.fromFile(context.getExternalFilesDir(null)!!)
+        get() = DocumentFile.fromFile(context.getExternalFilesDir(null) ?: context.filesDir)
 
     private fun getDefaultFileLocation(type: String): File? {
-        val externalFilesDir = context.getExternalFilesDir(null) ?: return null
-        val path = String.format("%s/%s", externalFilesDir.absolutePath, type)
-        val file = File(path)
-        return if (file.isDirectory || file.mkdirs()) file else null
+        val baseDir = context.getExternalFilesDir(null) ?: context.filesDir
+        val path = File(baseDir, type)
+        return if (path.isDirectory || path.mkdirs()) path else null
     }
 
     private fun hasWritePermission(context: Context, uri: Uri): Boolean =

app/src/main/java/org/tasks/preferences/PreferencesViewModel.kt

@@ -2,6 +2,7 @@ package org.tasks.preferences
 
 import android.content.ContentResolver
 import android.content.Context
+import android.net.Uri
 import androidx.documentfile.provider.DocumentFile
 import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
@@ -51,8 +52,16 @@ class PreferencesViewModel @Inject constructor(
         get() = isStale(lastDriveBackup.value) && isStale(lastAndroidBackup.value)
 
     val usingPrivateStorage: Boolean
-        get() = preferences.backupDirectory.let {
-            it == null || it.toString().startsWith(preferences.externalStorage.toString())
+        get() = preferences.backupDirectory.let { backupDir ->
+            val backupDirStr = backupDir?.toString() ?: return true
+            context
+                .getExternalFilesDir(null)
+                ?.let {
+                    if (backupDirStr.startsWith(Uri.fromFile(it).toString())) {
+                        return true
+                    }
+                }
+            return backupDirStr.startsWith(Uri.fromFile(context.filesDir).toString())
         }
 
     val driveAccount: String?

app/src/main/java/org/tasks/preferences/fragments/Backups.kt

@@ -257,7 +257,7 @@ class Backups : InjectingPreferenceFragment() {
             pref.summary = """
                 $location
 
-                ${requireContext().getString(R.string.backup_location_warning, FileHelper.uri2String(preferences.externalStorage))}
+                ${requireContext().getString(R.string.backup_location_warning, FileHelper.uri2String(preferences.appPrivateStorage))}
             """.trimIndent()
         } else {
             pref.icon = null