Merge pull request #42 from grote/usb

Various optimizations for using a USB flash drive as backup storage medium

app/src/androidTest/java/com/stevesoltys/backup/DocumentsStorageTest.kt

@@ -3,8 +3,6 @@ package com.stevesoltys.backup
 import androidx.documentfile.provider.DocumentFile
 import androidx.test.platform.app.InstrumentationRegistry
 import androidx.test.runner.AndroidJUnit4
-import com.stevesoltys.backup.settings.getBackupToken
-import com.stevesoltys.backup.settings.getStorage
 import com.stevesoltys.backup.transport.backup.plugins.DocumentsStorage
 import com.stevesoltys.backup.transport.backup.plugins.createOrGetFile
 import org.junit.After
@@ -21,9 +19,8 @@ private const val filename = "test-file"
 class DocumentsStorageTest {
 
     private val context = InstrumentationRegistry.getInstrumentation().targetContext
-    private val token = getBackupToken(context)
+    private val settingsManager = (context.applicationContext as Backup).settingsManager
-    private val folderUri = getStorage(context)
+    private val storage = DocumentsStorage(context, settingsManager)
-    private val storage = DocumentsStorage(context, folderUri, token)
 
     private lateinit var file: DocumentFile
 

app/src/main/AndroidManifest.xml

@@ -14,6 +14,16 @@
         android:name="android.permission.MANAGE_DOCUMENTS"
         tools:ignore="ProtectedPermissions" />
 
+    <!-- This is needed to access the serial number of USB mass storage devices -->
+    <uses-permission
+        android:name="android.permission.MANAGE_USB"
+        tools:ignore="ProtectedPermissions" />
+
+    <!-- This is needed to change system backup settings -->
+    <uses-permission
+        android:name="android.permission.WRITE_SECURE_SETTINGS"
+        tools:ignore="ProtectedPermissions" />
+
     <application
         android:name=".Backup"
         android:allowBackup="false"
@@ -72,5 +82,16 @@
             </intent-filter>
         </service>
 
+        <receiver
+            android:name=".UsbIntentReceiver"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
+            </intent-filter>
+            <meta-data
+                android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
+                android:resource="@xml/device_filter" />
+        </receiver>
+
     </application>
 </manifest>

app/src/main/java/com/stevesoltys/backup/Backup.kt

@@ -1,14 +1,14 @@
 package com.stevesoltys.backup
 
 import android.app.Application
+import android.app.backup.BackupManager.PACKAGE_MANAGER_SENTINEL
 import android.app.backup.IBackupManager
 import android.content.Context.BACKUP_SERVICE
-import android.net.Uri
 import android.os.Build
 import android.os.ServiceManager.getService
 import com.stevesoltys.backup.crypto.KeyManager
 import com.stevesoltys.backup.crypto.KeyManagerImpl
-import com.stevesoltys.backup.ui.storage.AUTHORITY_STORAGE
+import com.stevesoltys.backup.settings.SettingsManager
 
 /**
  * @author Steve Soltys
@@ -25,10 +25,15 @@ class Backup : Application() {
         }
     }
 
+    val settingsManager by lazy {
+        SettingsManager(this)
+    }
     val notificationManager by lazy {
         BackupNotificationManager(this)
     }
 
 }
 
+const val MAGIC_PACKAGE_MANAGER = PACKAGE_MANAGER_SENTINEL
+
 fun isDebugBuild() = Build.TYPE == "userdebug"

app/src/main/java/com/stevesoltys/backup/BackupNotificationManager.kt

@@ -79,9 +79,9 @@ class BackupNotificationManager(private val context: Context) {
         val notification = errorBuilder.apply {
             setContentTitle(context.getString(R.string.notification_error_title))
             setContentText(context.getString(R.string.notification_error_text))
-            addAction(action)
             setOnlyAlertOnce(true)
             setAutoCancel(true)
+            mActions = arrayListOf(action)
         }.build()
         nm.notify(NOTIFICATION_ID_ERROR, notification)
     }

app/src/main/java/com/stevesoltys/backup/NotificationBackupObserver.kt

@@ -68,7 +68,7 @@ class NotificationBackupObserver(context: Context, private val userInitiated: Bo
 }
 
 fun getAppName(pm: PackageManager, packageId: String): CharSequence {
-    if (packageId == "@pm@") return packageId
+    if (packageId == MAGIC_PACKAGE_MANAGER) return packageId
     val appInfo = pm.getApplicationInfo(packageId, 0)
     return pm.getApplicationLabel(appInfo)
 }

app/src/main/java/com/stevesoltys/backup/UsbIntentReceiver.kt

@@ -0,0 +1,104 @@
+package com.stevesoltys.backup
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.database.ContentObserver
+import android.hardware.usb.UsbDevice
+import android.hardware.usb.UsbInterface
+import android.hardware.usb.UsbManager.*
+import android.net.Uri
+import android.os.Handler
+import android.provider.DocumentsContract
+import android.util.Log
+import com.stevesoltys.backup.settings.FlashDrive
+import com.stevesoltys.backup.transport.requestBackup
+import com.stevesoltys.backup.ui.storage.AUTHORITY_STORAGE
+import java.util.*
+import java.util.concurrent.TimeUnit.HOURS
+
+private val TAG = UsbIntentReceiver::class.java.simpleName
+
+class UsbIntentReceiver : UsbMonitor() {
+
+    override fun shouldMonitorStatus(context: Context, action: String, device: UsbDevice): Boolean {
+        if (action != ACTION_USB_DEVICE_ATTACHED) return false
+        Log.d(TAG, "Checking if this is the current backup drive.")
+        val settingsManager = (context.applicationContext as Backup).settingsManager
+        val savedFlashDrive = settingsManager.getFlashDrive() ?: return false
+        val attachedFlashDrive = FlashDrive.from(device)
+        return if (savedFlashDrive == attachedFlashDrive) {
+            Log.d(TAG, "Matches stored device, checking backup time...")
+            if (Date().time - settingsManager.getBackupTime() >= HOURS.toMillis(24)) {
+                Log.d(TAG, "Last backup older than 24 hours, requesting a backup...")
+                true
+            } else {
+                Log.d(TAG, "We have a recent backup, not requesting a new one.")
+                false
+            }
+        } else {
+            Log.d(TAG, "Different device attached, ignoring...")
+            false
+        }
+    }
+
+    override fun onStatusChanged(context: Context, action: String, device: UsbDevice) {
+        Thread {
+            requestBackup(context)
+        }.start()
+    }
+
+}
+
+/**
+ * When we get the [ACTION_USB_DEVICE_ATTACHED] broadcast, the storage is not yet available.
+ * So we need to use a ContentObserver to request a backup only once available.
+ */
+abstract class UsbMonitor : BroadcastReceiver() {
+
+    override fun onReceive(context: Context, intent: Intent) {
+        val action = intent.action ?: return
+        if (intent.action == ACTION_USB_DEVICE_ATTACHED || intent.action == ACTION_USB_DEVICE_DETACHED) {
+            val device = intent.extras?.getParcelable<UsbDevice>(EXTRA_DEVICE) ?: return
+            Log.d(TAG, "New USB mass-storage device attached.")
+            device.log()
+
+            if (!shouldMonitorStatus(context, action, device)) return
+
+            val rootsUri = DocumentsContract.buildRootsUri(AUTHORITY_STORAGE)
+            val contentResolver = context.contentResolver
+            val observer = object : ContentObserver(Handler()) {
+                override fun onChange(selfChange: Boolean, uri: Uri?) {
+                    super.onChange(selfChange, uri)
+                    onStatusChanged(context, action, device)
+                    contentResolver.unregisterContentObserver(this)
+                }
+            }
+            contentResolver.registerContentObserver(rootsUri, true, observer)
+        }
+    }
+
+    abstract fun shouldMonitorStatus(context: Context, action: String, device: UsbDevice): Boolean
+
+    abstract fun onStatusChanged(context: Context, action: String, device: UsbDevice)
+
+}
+
+internal fun UsbDevice.isMassStorage(): Boolean {
+    for (i in 0 until interfaceCount) {
+        if (getInterface(i).isMassStorage()) return true
+    }
+    return false
+}
+
+private fun UsbInterface.isMassStorage(): Boolean {
+    return interfaceClass == 8 && interfaceProtocol == 80 && interfaceSubclass == 6
+}
+
+private fun UsbDevice.log() {
+    Log.d(TAG, "  name: $manufacturerName $productName")
+    Log.d(TAG, "  serialNumber: $serialNumber")
+    Log.d(TAG, "  productId: $productId")
+    Log.d(TAG, "  vendorId: $vendorId")
+    Log.d(TAG, "  isMassStorage: ${isMassStorage()}")
+}

app/src/main/java/com/stevesoltys/backup/activity/MainActivityController.java

@@ -18,8 +18,6 @@ import static android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION;
 import static android.content.Intent.FLAG_GRANT_WRITE_URI_PERMISSION;
 import static com.stevesoltys.backup.activity.MainActivity.OPEN_DOCUMENT_TREE_BACKUP_REQUEST_CODE;
 import static com.stevesoltys.backup.activity.MainActivity.OPEN_DOCUMENT_TREE_REQUEST_CODE;
-import static com.stevesoltys.backup.settings.SettingsManagerKt.getBackupPassword;
-import static com.stevesoltys.backup.settings.SettingsManagerKt.getStorage;
 
 /**
  * @author Steve Soltys
@@ -41,7 +39,7 @@ public class MainActivityController {
     }
 
     boolean isChangeBackupLocationButtonVisible(Activity parent) {
-        return getStorage(parent) != null;
+        return false;
     }
 
     private void showChooseFolderActivity(Activity parent, boolean continueToBackup) {
@@ -74,15 +72,8 @@ public class MainActivityController {
     }
 
     boolean onAutomaticBackupsButtonClicked(Activity parent) {
-        if (getStorage(parent) == null || getBackupPassword(parent) == null) {
+        Toast.makeText(parent, "Please make at least one manual backup first.", Toast.LENGTH_SHORT).show();
-            Toast.makeText(parent, "Please make at least one manual backup first.", Toast.LENGTH_SHORT).show();
+        return false;
-            return false;
-        }
-
-        // show Toast informing the user
-        Toast.makeText(parent, "REMOVED", Toast.LENGTH_SHORT).show();
-
-        return true;
     }
 
     void onChangeBackupLocationButtonClicked(Activity parent) {

app/src/main/java/com/stevesoltys/backup/activity/backup/CreateBackupActivityController.java

@@ -21,8 +21,6 @@ import com.stevesoltys.backup.service.backup.BackupService;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
 
-import static com.stevesoltys.backup.settings.SettingsManagerKt.getBackupPassword;
-
 /**
  * @author Steve Soltys
  */
@@ -70,12 +68,7 @@ class CreateBackupActivityController {
     }
 
     void onCreateBackupButtonClicked(Set<String> selectedPackages, Activity parent) {
-        String password = getBackupPassword(parent);
+        backupService.backupPackageData(selectedPackages, parent);
-        if (password == null) {
-            showEnterPasswordAlert(selectedPackages, parent);
-        } else {
-            backupService.backupPackageData(selectedPackages, parent);
-        }
     }
 
     private void showEnterPasswordAlert(Set<String> selectedPackages, Activity parent) {

app/src/main/java/com/stevesoltys/backup/restore/RestoreProgressFragment.kt

@@ -10,10 +10,10 @@ import android.view.WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
 import androidx.fragment.app.Fragment
 import androidx.lifecycle.Observer
 import androidx.lifecycle.ViewModelProviders
+import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.R
 import com.stevesoltys.backup.getAppName
 import com.stevesoltys.backup.isDebugBuild
-import com.stevesoltys.backup.settings.getStorage
 import kotlinx.android.synthetic.main.fragment_restore_progress.*
 
 class RestoreProgressFragment : Fragment() {
@@ -49,7 +49,8 @@ class RestoreProgressFragment : Fragment() {
             if (finished == 0) {
                 // success
                 currentPackageView.text = getString(R.string.restore_finished_success)
-                warningView.text = if (getStorage(requireContext())?.ejectable == true) {
+                val settingsManager = (requireContext().applicationContext as Backup).settingsManager
+                warningView.text = if (settingsManager.getStorage()?.isUsb == true) {
                     getString(R.string.restore_finished_warning_only_installed, getString(R.string.restore_finished_warning_ejectable))
                 } else {
                     getString(R.string.restore_finished_warning_only_installed, null)

app/src/main/java/com/stevesoltys/backup/service/PackageService.kt

@@ -8,6 +8,7 @@ import android.os.UserHandle
 import android.util.Log
 import com.google.android.collect.Sets.newArraySet
 import com.stevesoltys.backup.Backup
+import com.stevesoltys.backup.MAGIC_PACKAGE_MANAGER
 import java.util.*
 
 private val TAG = PackageService::class.java.simpleName
@@ -49,7 +50,7 @@ class PackageService {
 
             // add magic @pm@ package (PACKAGE_MANAGER_SENTINEL) which holds package manager data
             val packageArray = eligibleApps.toMutableList()
-            packageArray.add("@pm@")
+            packageArray.add(MAGIC_PACKAGE_MANAGER)
 
             return packageArray.toTypedArray()
         }

app/src/main/java/com/stevesoltys/backup/settings/BackupManagerSettings.kt

@@ -0,0 +1,38 @@
+package com.stevesoltys.backup.settings
+
+import android.content.ContentResolver
+import android.provider.Settings
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeUnit.DAYS
+
+private val SETTING = Settings.Secure.BACKUP_MANAGER_CONSTANTS
+private const val DELIMITER = ','
+
+private const val KEY_VALUE_BACKUP_INTERVAL_MILLISECONDS = "key_value_backup_interval_milliseconds"
+private const val FULL_BACKUP_INTERVAL_MILLISECONDS = "full_backup_interval_milliseconds"
+
+object BackupManagerSettings {
+
+    /**
+     * This clears the backup settings, so that default values will be used.
+     */
+    fun enableAutomaticBackups(resolver: ContentResolver) {
+        // setting this to null will cause the BackupManagerConstants to use default values
+        setSettingValue(resolver, null)
+    }
+
+    /**
+     * This sets the backup intervals to a longer than default value. Currently 30 days
+     */
+    fun disableAutomaticBackups(resolver: ContentResolver) {
+        val value = DAYS.toMillis(30)
+        val kv = "$KEY_VALUE_BACKUP_INTERVAL_MILLISECONDS=$value"
+        val full = "$FULL_BACKUP_INTERVAL_MILLISECONDS=$value"
+        setSettingValue(resolver, "$kv$DELIMITER$full")
+    }
+
+    private fun setSettingValue(resolver: ContentResolver, value: String?) {
+        Settings.Secure.putString(resolver, SETTING, value)
+    }
+
+}

app/src/main/java/com/stevesoltys/backup/settings/SettingsFragment.kt

@@ -1,11 +1,18 @@
 package com.stevesoltys.backup.settings
 
+import android.content.Context
 import android.content.Context.BACKUP_SERVICE
 import android.content.Intent
+import android.content.IntentFilter
+import android.hardware.usb.UsbDevice
+import android.hardware.usb.UsbManager.ACTION_USB_DEVICE_ATTACHED
+import android.hardware.usb.UsbManager.ACTION_USB_DEVICE_DETACHED
 import android.os.Bundle
 import android.os.RemoteException
 import android.provider.Settings
 import android.provider.Settings.Secure.BACKUP_AUTO_RESTORE
+import android.text.format.DateUtils.MINUTE_IN_MILLIS
+import android.text.format.DateUtils.getRelativeTimeSpanString
 import android.util.Log
 import android.view.Menu
 import android.view.MenuInflater
@@ -17,7 +24,10 @@ import androidx.preference.PreferenceFragmentCompat
 import androidx.preference.TwoStatePreference
 import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.R
+import com.stevesoltys.backup.UsbMonitor
+import com.stevesoltys.backup.isMassStorage
 import com.stevesoltys.backup.restore.RestoreActivity
+import java.util.*
 
 private val TAG = SettingsFragment::class.java.name
 
@@ -26,16 +36,35 @@ class SettingsFragment : PreferenceFragmentCompat() {
     private val backupManager = Backup.backupManager
 
     private lateinit var viewModel: SettingsViewModel
+    private lateinit var settingsManager: SettingsManager
 
     private lateinit var backup: TwoStatePreference
     private lateinit var autoRestore: TwoStatePreference
     private lateinit var backupLocation: Preference
 
+    private var menuBackupNow: MenuItem? = null
+    private var menuRestore: MenuItem? = null
+
+    private var storage: Storage? = null
+    private val usbFilter = IntentFilter(ACTION_USB_DEVICE_ATTACHED).apply {
+        addAction(ACTION_USB_DEVICE_DETACHED)
+    }
+    private val usbReceiver = object : UsbMonitor() {
+        override fun shouldMonitorStatus(context: Context, action: String, device: UsbDevice): Boolean {
+            return device.isMassStorage()
+        }
+
+        override fun onStatusChanged(context: Context, action: String, device: UsbDevice) {
+            setMenuItemStates()
+        }
+    }
+
     override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
         setPreferencesFromResource(R.xml.settings, rootKey)
         setHasOptionsMenu(true)
 
         viewModel = ViewModelProviders.of(requireActivity()).get(SettingsViewModel::class.java)
+        settingsManager = (requireContext().applicationContext as Backup).settingsManager
 
         backup = findPreference<TwoStatePreference>("backup")!!
         backup.onPreferenceChangeListener = OnPreferenceChangeListener { _, newValue ->
@@ -74,30 +103,31 @@ class SettingsFragment : PreferenceFragmentCompat() {
         super.onStart()
 
         // we need to re-set the title when returning to this fragment
-        requireActivity().setTitle(R.string.app_name)
+        activity?.setTitle(R.string.app_name)
 
-        try {
+        storage = settingsManager.getStorage()
-            backup.isChecked = backupManager.isBackupEnabled
+        setBackupState()
-            backup.isEnabled = true
+        setAutoRestoreState()
-        } catch (e: RemoteException) {
+        setBackupLocationSummary()
-            Log.e(TAG, "Error communicating with BackupManager", e)
+        setMenuItemStates()
-            backup.isEnabled = false
-        }
 
-        val resolver = requireContext().contentResolver
+        if (storage?.isUsb == true) context?.registerReceiver(usbReceiver, usbFilter)
-        autoRestore.isChecked = Settings.Secure.getInt(resolver, BACKUP_AUTO_RESTORE, 1) == 1
+    }
 
-        // TODO add time of last backup here
+    override fun onStop() {
-        val storageName = getStorage(requireContext())?.name
+        super.onStop()
-        backupLocation.summary = storageName ?: getString(R.string.settings_backup_location_none )
+        if (storage?.isUsb == true) context?.unregisterReceiver(usbReceiver)
     }
 
     override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
         super.onCreateOptionsMenu(menu, inflater)
         inflater.inflate(R.menu.settings_menu, menu)
+        menuBackupNow = menu.findItem(R.id.action_backup)
+        menuRestore = menu.findItem(R.id.action_restore)
         if (resources.getBoolean(R.bool.show_restore_in_settings)) {
-            menu.findItem(R.id.action_restore).isVisible = true
+            menuRestore?.isVisible = true
         }
+        setMenuItemStates()
     }
 
     override fun onOptionsItemSelected(item: MenuItem): Boolean = when {
@@ -112,4 +142,45 @@ class SettingsFragment : PreferenceFragmentCompat() {
         else -> super.onOptionsItemSelected(item)
     }
 
+    private fun setBackupState() {
+        try {
+            backup.isChecked = backupManager.isBackupEnabled
+            backup.isEnabled = true
+        } catch (e: RemoteException) {
+            Log.e(TAG, "Error communicating with BackupManager", e)
+            backup.isEnabled = false
+        }
+    }
+
+    private fun setAutoRestoreState() {
+        activity?.contentResolver?.let {
+            autoRestore.isChecked = Settings.Secure.getInt(it, BACKUP_AUTO_RESTORE, 1) == 1
+        }
+    }
+
+    private fun setBackupLocationSummary() {
+        // get name of storage location
+        val storageName = storage?.name ?: getString(R.string.settings_backup_location_none)
+
+        // get time of last backup
+        val lastBackupInMillis = settingsManager.getBackupTime()
+        val lastBackup = if (lastBackupInMillis == 0L) {
+            getString(R.string.settings_backup_last_backup_never)
+        } else {
+            getRelativeTimeSpanString(lastBackupInMillis, Date().time, MINUTE_IN_MILLIS, 0)
+        }
+        backupLocation.summary = getString(R.string.settings_backup_location_summary, storageName, lastBackup)
+    }
+
+    private fun setMenuItemStates() {
+        val context = context ?: return
+        if (menuBackupNow != null && menuRestore != null) {
+            val storage = this.storage
+            val enabled = storage != null &&
+                    (!storage.isUsb || storage.getDocumentFile(context).isDirectory)
+            menuBackupNow?.isEnabled = enabled
+            menuRestore?.isEnabled = enabled
+        }
+    }
+
 }

app/src/main/java/com/stevesoltys/backup/settings/SettingsManager.kt

@@ -1,59 +1,139 @@
 package com.stevesoltys.backup.settings
 
 import android.content.Context
+import android.hardware.usb.UsbDevice
 import android.net.Uri
-import android.preference.PreferenceManager.getDefaultSharedPreferences
+import androidx.documentfile.provider.DocumentFile
+import androidx.preference.PreferenceManager
 import java.util.*
 
 private const val PREF_KEY_STORAGE_URI = "storageUri"
 private const val PREF_KEY_STORAGE_NAME = "storageName"
-private const val PREF_KEY_STORAGE_EJECTABLE = "storageEjectable"
+private const val PREF_KEY_STORAGE_IS_USB = "storageIsUsb"
+
+private const val PREF_KEY_FLASH_DRIVE_NAME = "flashDriveName"
+private const val PREF_KEY_FLASH_DRIVE_SERIAL_NUMBER = "flashSerialNumber"
+private const val PREF_KEY_FLASH_DRIVE_VENDOR_ID = "flashDriveVendorId"
+private const val PREF_KEY_FLASH_DRIVE_PRODUCT_ID = "flashDriveProductId"
+
 private const val PREF_KEY_BACKUP_TOKEN = "backupToken"
+private const val PREF_KEY_BACKUP_TIME = "backupTime"
 private const val PREF_KEY_BACKUP_PASSWORD = "backupLegacyPassword"
 
+class SettingsManager(context: Context) {
+
+    private val prefs = PreferenceManager.getDefaultSharedPreferences(context)
+
+    fun setStorage(storage: Storage) {
+        prefs.edit()
+                .putString(PREF_KEY_STORAGE_URI, storage.uri.toString())
+                .putString(PREF_KEY_STORAGE_NAME, storage.name)
+                .putBoolean(PREF_KEY_STORAGE_IS_USB, storage.isUsb)
+                .apply()
+    }
+
+    fun getStorage(): Storage? {
+        val uriStr = prefs.getString(PREF_KEY_STORAGE_URI, null) ?: return null
+        val uri = Uri.parse(uriStr)
+        val name = prefs.getString(PREF_KEY_STORAGE_NAME, null) ?: throw IllegalStateException()
+        val isUsb = prefs.getBoolean(PREF_KEY_STORAGE_IS_USB, false)
+        return Storage(uri, name, isUsb)
+    }
+
+    fun setFlashDrive(usb: FlashDrive?) {
+        if (usb == null) {
+            prefs.edit()
+                    .remove(PREF_KEY_FLASH_DRIVE_NAME)
+                    .remove(PREF_KEY_FLASH_DRIVE_SERIAL_NUMBER)
+                    .remove(PREF_KEY_FLASH_DRIVE_VENDOR_ID)
+                    .remove(PREF_KEY_FLASH_DRIVE_PRODUCT_ID)
+                    .apply()
+        } else {
+            prefs.edit()
+                    .putString(PREF_KEY_FLASH_DRIVE_NAME, usb.name)
+                    .putString(PREF_KEY_FLASH_DRIVE_SERIAL_NUMBER, usb.serialNumber)
+                    .putInt(PREF_KEY_FLASH_DRIVE_VENDOR_ID, usb.vendorId)
+                    .putInt(PREF_KEY_FLASH_DRIVE_PRODUCT_ID, usb.productId)
+                    .apply()
+        }
+    }
+
+    fun getFlashDrive(): FlashDrive? {
+        val name = prefs.getString(PREF_KEY_FLASH_DRIVE_NAME, null) ?: return null
+        val serialNumber = prefs.getString(PREF_KEY_FLASH_DRIVE_SERIAL_NUMBER, null)
+        val vendorId = prefs.getInt(PREF_KEY_FLASH_DRIVE_VENDOR_ID, -1)
+        val productId = prefs.getInt(PREF_KEY_FLASH_DRIVE_PRODUCT_ID, -1)
+        return FlashDrive(name, serialNumber, vendorId, productId)
+    }
+
+    /**
+     * Generates and returns a new backup token while saving it as well.
+     * Subsequent calls to [getBackupToken] will return this new token once saved.
+     */
+    fun getAndSaveNewBackupToken(): Long = Date().time.apply {
+        prefs.edit()
+                .putLong(PREF_KEY_BACKUP_TOKEN, this)
+                .apply()
+    }
+
+    /**
+     * Returns the current backup token or 0 if none exists.
+     */
+    fun getBackupToken(): Long {
+        return prefs.getLong(PREF_KEY_BACKUP_TOKEN, 0L)
+    }
+
+    /**
+     * Sets the last backup time to "now".
+     */
+    fun saveNewBackupTime() {
+        prefs.edit()
+                .putLong(PREF_KEY_BACKUP_TIME, Date().time)
+                .apply()
+    }
+
+    /**
+     * Sets the last backup time to "never".
+     */
+    fun resetBackupTime() {
+        prefs.edit()
+                .putLong(PREF_KEY_BACKUP_TIME, 0L)
+                .apply()
+    }
+
+    /**
+     * Returns the last backup time in unix epoch milli seconds.
+     */
+    fun getBackupTime(): Long {
+        return prefs.getLong(PREF_KEY_BACKUP_TIME, 0L)
+    }
+
+    @Deprecated("Replaced by KeyManager#getBackupKey()")
+    fun getBackupPassword(): String? {
+        return prefs.getString(PREF_KEY_BACKUP_PASSWORD, null)
+    }
+
+}
+
 data class Storage(
         val uri: Uri,
         val name: String,
-        val ejectable: Boolean
+        val isUsb: Boolean) {
-)
+    fun getDocumentFile(context: Context) = DocumentFile.fromTreeUri(context, uri)
-
+            ?: throw AssertionError("Should only happen on API < 21.")
-fun setStorage(context: Context, storage: Storage) {
-    getDefaultSharedPreferences(context)
-            .edit()
-            .putString(PREF_KEY_STORAGE_URI, storage.uri.toString())
-            .putString(PREF_KEY_STORAGE_NAME, storage.name)
-            .putBoolean(PREF_KEY_STORAGE_EJECTABLE, storage.ejectable)
-            .apply()
 }
 
-fun getStorage(context: Context): Storage? {
+data class FlashDrive(
-    val prefs = getDefaultSharedPreferences(context)
+        val name: String,
-    val uriStr = prefs.getString(PREF_KEY_STORAGE_URI, null) ?: return null
+        val serialNumber: String?,
-    val uri = Uri.parse(uriStr)
+        val vendorId: Int,
-    val name = prefs.getString(PREF_KEY_STORAGE_NAME, null) ?: throw IllegalStateException()
+        val productId: Int) {
-    val ejectable = prefs.getBoolean(PREF_KEY_STORAGE_EJECTABLE, false)
+    companion object {
-    return Storage(uri, name, ejectable)
+        fun from(device: UsbDevice) = FlashDrive(
-}
+                name = "${device.manufacturerName} ${device.productName}",
-
+                serialNumber = device.serialNumber,
-/**
+                vendorId = device.vendorId,
- * Generates and returns a new backup token while saving it as well.
+                productId = device.productId
- * Subsequent calls to [getBackupToken] will return this new token once saved.
+        )
- */
+    }
-fun getAndSaveNewBackupToken(context: Context): Long = Date().time.apply {
-    getDefaultSharedPreferences(context)
-            .edit()
-            .putLong(PREF_KEY_BACKUP_TOKEN, this)
-            .apply()
-}
-
-/**
- * Returns the current backup token or 0 if none exists.
- */
-fun getBackupToken(context: Context): Long {
-    return getDefaultSharedPreferences(context).getLong(PREF_KEY_BACKUP_TOKEN, 0L)
-}
-
-@Deprecated("Replaced by KeyManager#getBackupKey()")
-fun getBackupPassword(context: Context): String? {
-    return getDefaultSharedPreferences(context).getString(PREF_KEY_BACKUP_PASSWORD, null)
 }

app/src/main/java/com/stevesoltys/backup/settings/SettingsViewModel.kt

@@ -1,20 +1,14 @@
 package com.stevesoltys.backup.settings
 
 import android.app.Application
-import com.stevesoltys.backup.Backup
-import com.stevesoltys.backup.R
 import com.stevesoltys.backup.transport.requestBackup
 import com.stevesoltys.backup.ui.RequireProvisioningViewModel
 
-private val TAG = SettingsViewModel::class.java.simpleName
-
 class SettingsViewModel(app: Application) : RequireProvisioningViewModel(app) {
 
     override val isRestoreOperation = false
 
     fun backupNow() {
-        val nm = (app as Backup).notificationManager
-        nm.onBackupUpdate(app.getString(R.string.notification_backup_starting), 0, 1, true)
         Thread { requestBackup(app) }.start()
     }
 

app/src/main/java/com/stevesoltys/backup/transport/ConfigurableBackupTransport.kt

@@ -7,7 +7,6 @@ import android.app.backup.RestoreSet
 import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageInfo
-import android.os.Build.VERSION.SDK_INT
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.settings.SettingsActivity
@@ -36,7 +35,7 @@ class ConfigurableBackupTransport internal constructor(private val context: Cont
     }
 
     override fun getTransportFlags(): Int {
-        return if (SDK_INT >= 28) FLAG_CLIENT_SIDE_ENCRYPTION_ENABLED else 0
+        return FLAG_CLIENT_SIDE_ENCRYPTION_ENABLED
     }
 
     override fun dataManagementIntent(): Intent {

app/src/main/java/com/stevesoltys/backup/transport/ConfigurableBackupTransportService.kt

@@ -14,6 +14,7 @@ import android.util.Log
 import androidx.annotation.WorkerThread
 import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.NotificationBackupObserver
+import com.stevesoltys.backup.R
 import com.stevesoltys.backup.service.PackageService
 import com.stevesoltys.backup.session.backup.BackupMonitor
 
@@ -50,7 +51,10 @@ class ConfigurableBackupTransportService : Service() {
 
 @WorkerThread
 fun requestBackup(context: Context) {
-    context.startService(Intent(context, ConfigurableBackupTransportService::class.java))
+    // show notification
+    val nm = (context.applicationContext as Backup).notificationManager
+    nm.onBackupUpdate(context.getString(R.string.notification_backup_starting), 0, 1, true)
+
     val observer = NotificationBackupObserver(context, true)
     val flags = FLAG_NON_INCREMENTAL_BACKUP or FLAG_USER_INITIATED
     val packages = PackageService().eligiblePackages

app/src/main/java/com/stevesoltys/backup/transport/PluginManager.kt

@@ -8,8 +8,6 @@ import com.stevesoltys.backup.header.HeaderReaderImpl
 import com.stevesoltys.backup.header.HeaderWriterImpl
 import com.stevesoltys.backup.metadata.MetadataReaderImpl
 import com.stevesoltys.backup.metadata.MetadataWriterImpl
-import com.stevesoltys.backup.settings.getBackupToken
-import com.stevesoltys.backup.settings.getStorage
 import com.stevesoltys.backup.transport.backup.BackupCoordinator
 import com.stevesoltys.backup.transport.backup.FullBackup
 import com.stevesoltys.backup.transport.backup.InputFactory
@@ -24,9 +22,10 @@ import com.stevesoltys.backup.transport.restore.plugins.DocumentsProviderRestore
 
 class PluginManager(context: Context) {
 
-    // We can think about using an injection framework such as Dagger to simplify this.
+    // We can think about using an injection framework such as Dagger, Koin or Kodein to simplify this.
 
-    private val storage = DocumentsStorage(context, getStorage(context), getBackupToken(context))
+    private val settingsManager = (context.applicationContext as Backup).settingsManager
+    private val storage = DocumentsStorage(context, settingsManager)
 
     private val headerWriter = HeaderWriterImpl()
     private val headerReader = HeaderReaderImpl()
@@ -42,7 +41,7 @@ class PluginManager(context: Context) {
     private val fullBackup = FullBackup(backupPlugin.fullBackupPlugin, inputFactory, headerWriter, crypto)
     private val notificationManager = (context.applicationContext as Backup).notificationManager
 
-    internal val backupCoordinator = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
+    internal val backupCoordinator = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, settingsManager, notificationManager)
 
 
     private val restorePlugin = DocumentsProviderRestorePlugin(storage)
@@ -50,6 +49,6 @@ class PluginManager(context: Context) {
     private val kvRestore = KVRestore(restorePlugin.kvRestorePlugin, outputFactory, headerReader, crypto)
     private val fullRestore = FullRestore(restorePlugin.fullRestorePlugin, outputFactory, headerReader, crypto)
 
-    internal val restoreCoordinator = RestoreCoordinator(context, restorePlugin, kvRestore, fullRestore, metadataReader)
+    internal val restoreCoordinator = RestoreCoordinator(settingsManager, restorePlugin, kvRestore, fullRestore, metadataReader)
 
 }

app/src/main/java/com/stevesoltys/backup/transport/backup/BackupCoordinator.kt

@@ -1,15 +1,16 @@
 package com.stevesoltys.backup.transport.backup
 
-import android.app.backup.BackupTransport.TRANSPORT_ERROR
+import android.app.backup.BackupTransport.*
-import android.app.backup.BackupTransport.TRANSPORT_OK
 import android.content.Context
 import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.BackupNotificationManager
+import com.stevesoltys.backup.MAGIC_PACKAGE_MANAGER
 import com.stevesoltys.backup.metadata.MetadataWriter
-import com.stevesoltys.backup.settings.getBackupToken
+import com.stevesoltys.backup.settings.SettingsManager
 import java.io.IOException
+import java.util.concurrent.TimeUnit.DAYS
 
 private val TAG = BackupCoordinator::class.java.simpleName
 
@@ -23,6 +24,7 @@ class BackupCoordinator(
         private val kv: KVBackup,
         private val full: FullBackup,
         private val metadataWriter: MetadataWriter,
+        private val settingsManager: SettingsManager,
         private val nm: BackupNotificationManager) {
 
     private var calledInitialize = false
@@ -54,14 +56,15 @@ class BackupCoordinator(
         Log.i(TAG, "Initialize Device!")
         return try {
             plugin.initializeDevice()
-            writeBackupMetadata(getBackupToken(context))
+            writeBackupMetadata(settingsManager.getBackupToken())
             // [finishBackup] will only be called when we return [TRANSPORT_OK] here
             // so we remember that we initialized successfully
             calledInitialize = true
             TRANSPORT_OK
         } catch (e: IOException) {
             Log.e(TAG, "Error initializing device", e)
-            nm.onBackupError()
+            // Show error notification if we were ready for backups
+            if (getBackupBackoff() == 0L) nm.onBackupError()
             TRANSPORT_ERROR
         }
     }
@@ -83,21 +86,61 @@ class BackupCoordinator(
     // Key/value incremental backup support
     //
 
-    fun requestBackupTime() = kv.requestBackupTime()
+    /**
+     * Verify that this is a suitable time for a key/value backup pass.
+     * This should return zero if a backup is reasonable right now, some positive value otherwise.
+     * This method will be called outside of the [performIncrementalBackup]/[finishBackup] pair.
+     *
+     * If this is not a suitable time for a backup, the transport should return a backoff delay,
+     * in milliseconds, after which the Backup Manager should try again.
+     *
+     * @return Zero if this is a suitable time for a backup pass, or a positive time delay
+     *   in milliseconds to suggest deferring the backup pass for a while.
+     */
+    fun requestBackupTime(): Long = getBackupBackoff().apply {
+        Log.i(TAG, "Request incremental backup time. Returned $this")
+    }
 
-    fun performIncrementalBackup(packageInfo: PackageInfo, data: ParcelFileDescriptor, flags: Int) =
+    fun performIncrementalBackup(packageInfo: PackageInfo, data: ParcelFileDescriptor, flags: Int): Int {
-            kv.performBackup(packageInfo, data, flags)
+        // backups of package manager metadata do not respect backoff
+        // we need to reject them manually when now is not a good time for a backup
+        if (packageInfo.packageName == MAGIC_PACKAGE_MANAGER && getBackupBackoff() != 0L) {
+            return TRANSPORT_PACKAGE_REJECTED
+        }
+
+        val result = kv.performBackup(packageInfo, data, flags)
+        if (result == TRANSPORT_OK) settingsManager.saveNewBackupTime()
+        return result
+    }
 
     // ------------------------------------------------------------------------------------
     // Full backup
     //
 
-    fun requestFullBackupTime() = full.requestFullBackupTime()
+    /**
+     * Verify that this is a suitable time for a full-data backup pass.
+     * This should return zero if a backup is reasonable right now, some positive value otherwise.
+     * This method will be called outside of the [performFullBackup]/[finishBackup] pair.
+     *
+     * If this is not a suitable time for a backup, the transport should return a backoff delay,
+     * in milliseconds, after which the Backup Manager should try again.
+     *
+     * @return Zero if this is a suitable time for a backup pass, or a positive time delay
+     *   in milliseconds to suggest deferring the backup pass for a while.
+     *
+     * @see [requestBackupTime]
+     */
+    fun requestFullBackupTime(): Long = getBackupBackoff().apply {
+        Log.i(TAG, "Request full backup time. Returned $this")
+    }
 
     fun checkFullBackupSize(size: Long) = full.checkFullBackupSize(size)
 
-    fun performFullBackup(targetPackage: PackageInfo, fileDescriptor: ParcelFileDescriptor, flags: Int) =
+    fun performFullBackup(targetPackage: PackageInfo, fileDescriptor: ParcelFileDescriptor, flags: Int): Int {
-            full.performFullBackup(targetPackage, fileDescriptor, flags)
+        val result = full.performFullBackup(targetPackage, fileDescriptor, flags)
+        if (result == TRANSPORT_OK) settingsManager.saveNewBackupTime()
+        return result
+    }
 
     fun sendBackupData(numBytes: Int) = full.sendBackupData(numBytes)
 
@@ -156,4 +199,16 @@ class BackupCoordinator(
         metadataWriter.write(outputStream, token)
     }
 
+    private fun getBackupBackoff(): Long {
+        val noBackoff = 0L
+        val defaultBackoff = DAYS.toMillis(30)
+
+        // back off if there's no storage set
+        val storage = settingsManager.getStorage() ?: return defaultBackoff
+        // don't back off if storage is not ejectable or available right now
+        return if (!storage.isUsb || storage.getDocumentFile(context).isDirectory) noBackoff
+        // otherwise back off
+        else defaultBackoff
+    }
+
 }

app/src/main/java/com/stevesoltys/backup/transport/backup/FullBackup.kt

@@ -36,11 +36,6 @@ class FullBackup(
 
     fun hasState() = state != null
 
-    fun requestFullBackupTime(): Long {
-        Log.i(TAG, "Request full backup time")
-        return 0
-    }
-
     fun getQuota(): Long = plugin.getQuota()
 
     fun checkFullBackupSize(size: Long): Int {

app/src/main/java/com/stevesoltys/backup/transport/backup/KVBackup.kt

@@ -27,11 +27,6 @@ class KVBackup(
 
     fun hasState() = state != null
 
-    fun requestBackupTime(): Long {
-        Log.i(TAG, "Request K/V backup time")
-        return 0
-    }
-
     fun getQuota(): Long = plugin.getQuota()
 
     fun performBackup(packageInfo: PackageInfo, data: ParcelFileDescriptor, flags: Int): Int {

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt

@@ -42,7 +42,7 @@ class DocumentsProviderBackupPlugin(
     }
 
     override val providerPackageName: String? by lazy {
-        val authority = storage.rootBackupDir?.uri?.authority ?: return@lazy null
+        val authority = storage.getAuthority() ?: return@lazy null
         val providerInfo = packageManager.resolveContentProvider(authority, 0) ?: return@lazy null
         providerInfo.packageName
     }

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsStorage.kt

@@ -4,8 +4,8 @@ import android.content.Context
 import android.content.pm.PackageInfo
 import android.util.Log
 import androidx.documentfile.provider.DocumentFile
+import com.stevesoltys.backup.settings.SettingsManager
 import com.stevesoltys.backup.settings.Storage
-import com.stevesoltys.backup.settings.getAndSaveNewBackupToken
 import java.io.IOException
 import java.io.InputStream
 import java.io.OutputStream
@@ -19,12 +19,13 @@ private const val MIME_TYPE = "application/octet-stream"
 
 private val TAG = DocumentsStorage::class.java.simpleName
 
-class DocumentsStorage(private val context: Context, storage: Storage?, token: Long) {
+class DocumentsStorage(private val context: Context, private val settingsManager: SettingsManager) {
+
+    private val storage: Storage? = settingsManager.getStorage()
+    private val token: Long = settingsManager.getBackupToken()
 
     internal val rootBackupDir: DocumentFile? by lazy {
-        val folderUri = storage?.uri ?: return@lazy null
+        val parent = storage?.getDocumentFile(context) ?: return@lazy null
-        // [fromTreeUri] should only return null when SDK_INT < 21
-        val parent = DocumentFile.fromTreeUri(context, folderUri) ?: throw AssertionError()
         try {
             val rootDir = parent.createOrGetDirectory(DIRECTORY_ROOT)
             // create .nomedia file to prevent Android's MediaScanner from trying to index the backup
@@ -38,7 +39,7 @@ class DocumentsStorage(private val context: Context, storage: Storage?, token: L
 
     private val currentToken: Long by lazy {
         if (token != 0L) token
-        else getAndSaveNewBackupToken(context).apply {
+        else settingsManager.getAndSaveNewBackupToken().apply {
             Log.d(TAG, "Using a fresh backup token: $this")
         }
     }
@@ -71,6 +72,8 @@ class DocumentsStorage(private val context: Context, storage: Storage?, token: L
         }
     }
 
+    fun getAuthority(): String? = storage?.uri?.authority
+
     fun getSetDir(token: Long = currentToken): DocumentFile? {
         if (token == currentToken) return currentSetDir
         return rootBackupDir?.findFile(token.toString())

app/src/main/java/com/stevesoltys/backup/transport/restore/RestoreCoordinator.kt

@@ -5,14 +5,13 @@ import android.app.backup.BackupTransport.TRANSPORT_OK
 import android.app.backup.RestoreDescription
 import android.app.backup.RestoreDescription.*
 import android.app.backup.RestoreSet
-import android.content.Context
 import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.header.UnsupportedVersionException
 import com.stevesoltys.backup.metadata.DecryptionFailedException
 import com.stevesoltys.backup.metadata.MetadataReader
-import com.stevesoltys.backup.settings.getBackupToken
+import com.stevesoltys.backup.settings.SettingsManager
 import libcore.io.IoUtils.closeQuietly
 import java.io.IOException
 
@@ -23,7 +22,7 @@ private class RestoreCoordinatorState(
 private val TAG = RestoreCoordinator::class.java.simpleName
 
 internal class RestoreCoordinator(
-        private val context: Context,
+        private val settingsManager: SettingsManager,
         private val plugin: RestorePlugin,
         private val kv: KVRestore,
         private val full: FullRestore,
@@ -75,7 +74,7 @@ internal class RestoreCoordinator(
      * or 0 if there is no backup set available corresponding to the current device state.
      */
     fun getCurrentRestoreSet(): Long {
-        return getBackupToken(context)
+        return settingsManager.getBackupToken()
                 .apply { Log.i(TAG, "Got current restore set token: $this") }
     }
 

app/src/main/java/com/stevesoltys/backup/ui/storage/BackupStorageViewModel.kt

@@ -1,18 +1,16 @@
 package com.stevesoltys.backup.ui.storage
 
-import android.app.ActivityManager
 import android.app.Application
 import android.app.backup.BackupProgress
 import android.app.backup.IBackupObserver
 import android.net.Uri
 import android.os.UserHandle
-import android.os.UserManager
 import android.util.Log
 import androidx.annotation.WorkerThread
 import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.R
-import com.stevesoltys.backup.settings.getAndSaveNewBackupToken
 import com.stevesoltys.backup.transport.TRANSPORT_ID
+import com.stevesoltys.backup.transport.requestBackup
 
 private val TAG = BackupStorageViewModel::class.java.simpleName
 
@@ -21,14 +19,19 @@ internal class BackupStorageViewModel(private val app: Application) : StorageVie
     override val isRestoreOperation = false
 
     override fun onLocationSet(uri: Uri) {
-        saveStorage(uri)
+        val isUsb = saveStorage(uri)
 
         // use a new backup token
-        getAndSaveNewBackupToken(app)
+        settingsManager.getAndSaveNewBackupToken()
 
         // initialize the new location
         val observer = InitializationObserver()
         Backup.backupManager.initializeTransportsForUser(UserHandle.myUserId(), arrayOf(TRANSPORT_ID), observer)
+
+        // if storage is on USB and this is not SetupWizard, do a backup right away
+        if (isUsb && !isSetupWizard) Thread {
+            requestBackup(app)
+        }.start()
     }
 
     @WorkerThread

app/src/main/java/com/stevesoltys/backup/ui/storage/StorageActivity.kt

@@ -31,6 +31,7 @@ class StorageActivity : BackupActivity() {
         } else {
             ViewModelProviders.of(this).get(BackupStorageViewModel::class.java)
         }
+        viewModel.isSetupWizard = isSetupWizard()
 
         viewModel.locationSet.observeEvent(this, LiveEventHandler {
             showFragment(StorageCheckFragment.newInstance(getCheckFragmentTitle()), true)

app/src/main/java/com/stevesoltys/backup/ui/storage/StorageRootFetcher.kt

@@ -33,7 +33,7 @@ data class StorageRoot(
         internal val title: String,
         internal val summary: String?,
         internal val availableBytes: Long?,
-        internal val supportsEject: Boolean,
+        internal val isUsb: Boolean,
         internal val enabled: Boolean = true) {
 
     internal val uri: Uri by lazy {
@@ -41,7 +41,7 @@ data class StorageRoot(
     }
 
     fun isInternal(): Boolean {
-        return authority == AUTHORITY_STORAGE && !supportsEject
+        return authority == AUTHORITY_STORAGE && !isUsb
     }
 }
 
@@ -103,7 +103,7 @@ internal class StorageRootFetcher(private val context: Context) {
         var cursor: Cursor? = null
         try {
             cursor = contentResolver.query(rootsUri, null, null, null, null)
-            while (cursor.moveToNext()) {
+            while (cursor!!.moveToNext()) {
                 val root = getStorageRoot(authority, cursor)
                 if (root != null) roots.add(root)
             }
@@ -122,7 +122,6 @@ internal class StorageRootFetcher(private val context: Context) {
         if (!supportsCreate || !supportsIsChild) return null
         val rootId = cursor.getString(COLUMN_ROOT_ID)!!
         if (authority == AUTHORITY_STORAGE && rootId == ROOT_ID_HOME) return null
-        val supportsEject = flags and FLAG_SUPPORTS_EJECT != 0
         return StorageRoot(
                 authority = authority,
                 rootId = rootId,
@@ -131,13 +130,13 @@ internal class StorageRootFetcher(private val context: Context) {
                 title = cursor.getString(COLUMN_TITLE)!!,
                 summary = cursor.getString(COLUMN_SUMMARY),
                 availableBytes = cursor.getLong(COLUMN_AVAILABLE_BYTES),
-                supportsEject = supportsEject
+                isUsb = flags and FLAG_REMOVABLE_USB != 0
         )
     }
 
     private fun checkOrAddUsbRoot(roots: ArrayList<StorageRoot>) {
         for (root in roots) {
-            if (root.authority == AUTHORITY_STORAGE && root.supportsEject) return
+            if (root.authority == AUTHORITY_STORAGE && root.isUsb) return
         }
         val root = StorageRoot(
                 authority = AUTHORITY_STORAGE,
@@ -147,7 +146,7 @@ internal class StorageRootFetcher(private val context: Context) {
                 title = context.getString(R.string.storage_fake_drive_title),
                 summary = context.getString(R.string.storage_fake_drive_summary),
                 availableBytes = null,
-                supportsEject = true,
+                isUsb = true,
                 enabled = false
         )
         roots.add(root)
@@ -198,7 +197,7 @@ internal class StorageRootFetcher(private val context: Context) {
         }
     }
 
-    private fun getPackageIcon(context: Context, authority: String?, icon: Int): Drawable? {
+    private fun getPackageIcon(context: Context, authority: String, icon: Int): Drawable? {
         if (icon != 0) {
             val pm = context.packageManager
             val info = pm.resolveContentProvider(authority, 0)

app/src/main/java/com/stevesoltys/backup/ui/storage/StorageViewModel.kt

@@ -2,19 +2,22 @@ package com.stevesoltys.backup.ui.storage
 
 import android.app.Application
 import android.content.Context
+import android.content.Context.USB_SERVICE
 import android.content.Intent
 import android.content.Intent.FLAG_GRANT_READ_URI_PERMISSION
 import android.content.Intent.FLAG_GRANT_WRITE_URI_PERMISSION
+import android.hardware.usb.UsbManager
 import android.net.Uri
 import android.util.Log
-import androidx.documentfile.provider.DocumentFile
 import androidx.lifecycle.AndroidViewModel
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.MutableLiveData
+import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.R
+import com.stevesoltys.backup.isMassStorage
+import com.stevesoltys.backup.settings.BackupManagerSettings
+import com.stevesoltys.backup.settings.FlashDrive
 import com.stevesoltys.backup.settings.Storage
-import com.stevesoltys.backup.settings.getStorage
-import com.stevesoltys.backup.settings.setStorage
 import com.stevesoltys.backup.transport.ConfigurableBackupTransportService
 import com.stevesoltys.backup.ui.LiveEvent
 import com.stevesoltys.backup.ui.MutableLiveEvent
@@ -23,6 +26,8 @@ private val TAG = StorageViewModel::class.java.simpleName
 
 internal abstract class StorageViewModel(private val app: Application) : AndroidViewModel(app), RemovableStorageListener {
 
+    protected val settingsManager = (app as Backup).settingsManager
+
     private val mStorageRoots = MutableLiveData<List<StorageRoot>>()
     internal val storageRoots: LiveData<List<StorageRoot>> get() = mStorageRoots
 
@@ -35,14 +40,15 @@ internal abstract class StorageViewModel(private val app: Application) : Android
     private val storageRootFetcher by lazy { StorageRootFetcher(app) }
     private var storageRoot: StorageRoot? = null
 
+    internal var isSetupWizard: Boolean = false
     abstract val isRestoreOperation: Boolean
 
     companion object {
         internal fun validLocationIsSet(context: Context): Boolean {
-            val storage = getStorage(context) ?: return false
+            val settingsManager = (context.applicationContext as Backup).settingsManager
-            if (storage.ejectable) return true
+            val storage = settingsManager.getStorage() ?: return false
-            val file = DocumentFile.fromTreeUri(context, storage.uri) ?: return false
+            if (storage.isUsb) return true
-            return file.isDirectory
+            return storage.getDocumentFile(context).isDirectory
         }
     }
 
@@ -74,9 +80,12 @@ internal abstract class StorageViewModel(private val app: Application) : Android
         onLocationSet(uri)
     }
 
-    abstract fun onLocationSet(uri: Uri)
+    /**
-
+     * Saves the storage behind the given [Uri] (and saved [storageRoot]).
-    protected fun saveStorage(uri: Uri) {
+     *
+     * @return true if the storage is a USB flash drive, false otherwise.
+     */
+    protected fun saveStorage(uri: Uri): Boolean {
         // store backup storage location in settings
         val root = storageRoot ?: throw IllegalStateException()
         val name = if (root.isInternal()) {
@@ -84,15 +93,47 @@ internal abstract class StorageViewModel(private val app: Application) : Android
         } else {
             root.title
         }
-        val storage = Storage(uri, name, root.supportsEject)
+        val storage = Storage(uri, name, root.isUsb)
-        setStorage(app, storage)
+        settingsManager.setStorage(storage)
+
+        // reset time of last backup to "Never"
+        settingsManager.resetBackupTime()
+
+        if (storage.isUsb) {
+            Log.d(TAG, "Selected storage is a removable USB device.")
+            val wasSaved = saveUsbDevice()
+            // reset stored flash drive, if we did not update it
+            if (!wasSaved) settingsManager.setFlashDrive(null)
+            BackupManagerSettings.disableAutomaticBackups(app.contentResolver)
+        } else {
+            settingsManager.setFlashDrive(null)
+            BackupManagerSettings.enableAutomaticBackups(app.contentResolver)
+        }
 
         // stop backup service to be sure the old location will get updated
         app.stopService(Intent(app, ConfigurableBackupTransportService::class.java))
 
         Log.d(TAG, "New storage location saved: $uri")
+
+        return storage.isUsb
     }
 
+    private fun saveUsbDevice(): Boolean {
+        val manager = app.getSystemService(USB_SERVICE) as UsbManager
+        manager.deviceList.values.forEach { device ->
+            if (device.isMassStorage()) {
+                val flashDrive = FlashDrive.from(device)
+                settingsManager.setFlashDrive(flashDrive)
+                Log.d(TAG, "Saved flash drive: $flashDrive")
+                return true
+            }
+        }
+        Log.e(TAG, "No USB device found even though we were expecting one.")
+        return false
+    }
+
+    abstract fun onLocationSet(uri: Uri)
+
     override fun onCleared() {
         storageRootFetcher.setRemovableStorageListener(null)
         super.onCleared()

app/src/main/res/menu/settings_menu.xml

@@ -5,11 +5,13 @@
 
     <item
         android:id="@+id/action_backup"
+        android:enabled="false"
         android:title="@string/settings_backup_now"
         app:showAsAction="never" />
 
     <item
         android:id="@+id/action_restore"
+        android:enabled="false"
         android:title="@string/restore_backup_button"
         android:visible="false"
         app:showAsAction="never"

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

@@ -31,6 +31,8 @@
     <string name="settings_backup_location_invalid">The chosen location can not be used.</string>
     <string name="settings_backup_location_none">None</string>
     <string name="settings_backup_location_internal">Internal Storage</string>
+    <string name="settings_backup_last_backup_never">Never</string>
+    <string name="settings_backup_location_summary">%s · Last Backup %s</string>
     <string name="settings_info">All backups are encrypted on your phone. To restore from backup you will need your 12-word recovery code.</string>
     <string name="settings_auto_restore_title">Automatic restore</string>
     <string name="settings_auto_restore_summary">When reinstalling an app, restore backed up settings and data</string>

app/src/main/res/xml/device_filter.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <usb-device
+        class="8"
+        protocol="80"
+        subclass="6" />
+</resources>

app/src/test/java/com/stevesoltys/backup/transport/CoordinatorIntegrationTest.kt

@@ -43,14 +43,14 @@ internal class CoordinatorIntegrationTest : TransportTest() {
     private val fullBackupPlugin = mockk<FullBackupPlugin>()
     private val fullBackup = FullBackup(fullBackupPlugin, inputFactory, headerWriter, cryptoImpl)
     private val notificationManager = mockk<BackupNotificationManager>()
-    private val backup = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, notificationManager)
+    private val backup = BackupCoordinator(context, backupPlugin, kvBackup, fullBackup, metadataWriter, settingsManager, notificationManager)
 
     private val restorePlugin = mockk<RestorePlugin>()
     private val kvRestorePlugin = mockk<KVRestorePlugin>()
     private val kvRestore = KVRestore(kvRestorePlugin, outputFactory, headerReader, cryptoImpl)
     private val fullRestorePlugin = mockk<FullRestorePlugin>()
     private val fullRestore = FullRestore(fullRestorePlugin, outputFactory, headerReader, cryptoImpl)
-    private val restore = RestoreCoordinator(context, restorePlugin, kvRestore, fullRestore, metadataReader)
+    private val restore = RestoreCoordinator(settingsManager, restorePlugin, kvRestore, fullRestore, metadataReader)
 
     private val backupDataInput = mockk<BackupDataInput>()
     private val fileDescriptor = mockk<ParcelFileDescriptor>(relaxed = true)
@@ -91,6 +91,7 @@ internal class CoordinatorIntegrationTest : TransportTest() {
             appData2.size
         }
         every { kvBackupPlugin.getOutputStreamForRecord(packageInfo, key264) } returns bOutputStream2
+        every { settingsManager.saveNewBackupTime() } just Runs
 
         // start and finish K/V backup
         assertEquals(TRANSPORT_OK, backup.performIncrementalBackup(packageInfo, fileDescriptor, 0))
@@ -130,6 +131,7 @@ internal class CoordinatorIntegrationTest : TransportTest() {
         every { fullBackupPlugin.getOutputStream(packageInfo) } returns bOutputStream
         every { inputFactory.getInputStream(fileDescriptor) } returns bInputStream
         every { fullBackupPlugin.getQuota() } returns DEFAULT_QUOTA_FULL_BACKUP
+        every { settingsManager.saveNewBackupTime() } just Runs
 
         // perform backup to output stream
         assertEquals(TRANSPORT_OK, backup.performFullBackup(packageInfo, fileDescriptor, 0))

app/src/test/java/com/stevesoltys/backup/transport/TransportTest.kt

@@ -4,6 +4,7 @@ import android.content.Context
 import android.content.pm.PackageInfo
 import android.util.Log
 import com.stevesoltys.backup.crypto.Crypto
+import com.stevesoltys.backup.settings.SettingsManager
 import io.mockk.every
 import io.mockk.mockk
 import io.mockk.mockkStatic
@@ -14,6 +15,7 @@ import org.junit.jupiter.api.TestInstance.Lifecycle.PER_METHOD
 abstract class TransportTest {
 
     protected val crypto = mockk<Crypto>()
+    protected val settingsManager = mockk<SettingsManager>()
     protected val context = mockk<Context>(relaxed = true)
 
     protected val packageInfo = PackageInfo().apply { packageName = "org.example" }

app/src/test/java/com/stevesoltys/backup/transport/backup/BackupCoordinatorTest.kt

@@ -2,8 +2,12 @@ package com.stevesoltys.backup.transport.backup
 
 import android.app.backup.BackupTransport.TRANSPORT_ERROR
 import android.app.backup.BackupTransport.TRANSPORT_OK
+import android.net.Uri
+import androidx.documentfile.provider.DocumentFile
 import com.stevesoltys.backup.BackupNotificationManager
+import com.stevesoltys.backup.getRandomString
 import com.stevesoltys.backup.metadata.MetadataWriter
+import com.stevesoltys.backup.settings.Storage
 import io.mockk.Runs
 import io.mockk.every
 import io.mockk.just
@@ -23,14 +27,15 @@ internal class BackupCoordinatorTest: BackupTest() {
     private val metadataWriter = mockk<MetadataWriter>()
     private val notificationManager = mockk<BackupNotificationManager>()
 
-    private val backup = BackupCoordinator(context, plugin, kv, full, metadataWriter, notificationManager)
+    private val backup = BackupCoordinator(context, plugin, kv, full, metadataWriter, settingsManager, notificationManager)
 
     private val metadataOutputStream = mockk<OutputStream>()
 
     @Test
     fun `device initialization succeeds and delegates to plugin`() {
         every { plugin.initializeDevice() } just Runs
-        expectWritingMetadata(0L)
+        every { settingsManager.getBackupToken() } returns token
+        expectWritingMetadata(token)
         every { kv.hasState() } returns false
         every { full.hasState() } returns false
 
@@ -39,8 +44,11 @@ internal class BackupCoordinatorTest: BackupTest() {
     }
 
     @Test
-    fun `device initialization fails`() {
+    fun `error notification when device initialization fails`() {
+        val storage = Storage(Uri.EMPTY, getRandomString(), false)
+
         every { plugin.initializeDevice() } throws IOException()
+        every { settingsManager.getStorage() } returns storage
         every { notificationManager.onBackupError() } just Runs
 
         assertEquals(TRANSPORT_ERROR, backup.initializeDevice())
@@ -53,6 +61,27 @@ internal class BackupCoordinatorTest: BackupTest() {
         }
     }
 
+    @Test
+    fun `no error notification when device initialization fails on unplugged USB storage`() {
+        val storage = mockk<Storage>()
+        val documentFile = mockk<DocumentFile>()
+
+        every { plugin.initializeDevice() } throws IOException()
+        every { settingsManager.getStorage() } returns storage
+        every { storage.isUsb } returns true
+        every { storage.getDocumentFile(context) } returns documentFile
+        every { documentFile.isDirectory } returns false
+
+        assertEquals(TRANSPORT_ERROR, backup.initializeDevice())
+
+        // finish will only be called when TRANSPORT_OK is returned, so it should throw
+        every { kv.hasState() } returns false
+        every { full.hasState() } returns false
+        assertThrows(IllegalStateException::class.java) {
+            backup.finishBackup()
+        }
+    }
+
     @Test
     fun `getBackupQuota() delegates to right plugin`() {
         val isFullBackup = Random.nextBoolean()

app/src/test/java/com/stevesoltys/backup/transport/backup/FullBackupTest.kt

@@ -20,11 +20,6 @@ internal class FullBackupTest : BackupTest() {
     private val closeBytes = ByteArray(42).apply { Random.nextBytes(this) }
     private val inputStream = mockk<FileInputStream>()
 
-    @Test
-    fun `now is a good time for a backup`() {
-        assertEquals(0, backup.requestFullBackupTime())
-    }
-
     @Test
     fun `has no initial state`() {
         assertFalse(backup.hasState())

app/src/test/java/com/stevesoltys/backup/transport/backup/KVBackupTest.kt

@@ -28,11 +28,6 @@ internal class KVBackupTest : BackupTest() {
     private val value = ByteArray(23).apply { Random.nextBytes(this) }
     private val versionHeader = VersionHeader(packageName = packageInfo.packageName, key = key)
 
-    @Test
-    fun `now is a good time for a backup`() {
-        assertEquals(0, backup.requestBackupTime())
-    }
-
     @Test
     fun `has no initial state`() {
         assertFalse(backup.hasState())

app/src/test/java/com/stevesoltys/backup/transport/restore/RestoreCoordinatorTest.kt

@@ -27,7 +27,7 @@ internal class RestoreCoordinatorTest : TransportTest() {
     private val full = mockk<FullRestore>()
     private val metadataReader = mockk<MetadataReader>()
 
-    private val restore = RestoreCoordinator(context, plugin, kv, full, metadataReader)
+    private val restore = RestoreCoordinator(settingsManager, plugin, kv, full, metadataReader)
 
     private val token = Random.nextLong()
     private val inputStream = mockk<InputStream>()
@@ -56,8 +56,8 @@ internal class RestoreCoordinatorTest : TransportTest() {
 
     @Test
     fun `getCurrentRestoreSet() delegates to plugin`() {
-        // We don't mock the SettingsManager, so the default value is returned here
+        every { settingsManager.getBackupToken() } returns token
-        assertEquals(0L, restore.getCurrentRestoreSet())
+        assertEquals(token, restore.getCurrentRestoreSet())
     }
 
     @Test

permissions_com.stevesoltys.backup.xml

@@ -2,5 +2,7 @@
 <permissions>
     <privapp-permissions package="com.stevesoltys.backup">
         <permission name="android.permission.BACKUP"/>
+        <permission name="android.permission.MANAGE_USB"/>
+        <permission name="android.permission.WRITE_SECURE_SETTINGS"/>
     </privapp-permissions>
 </permissions>