show the root access toggle only if root is available

app/src/main/kotlin/com/simplemobiletools/filemanager/Config.kt

@@ -68,6 +68,10 @@ class Config(context: Context) : BaseConfig(context) {
 
     fun hasCustomSorting(path: String) = prefs.contains(SORT_FOLDER_PREFIX + path)
 
+    var isRootAvailable: Boolean
+        get() = prefs.getBoolean(IS_ROOT_AVAILABLE, false)
+        set(isRootAvailable) = prefs.edit().putBoolean(IS_ROOT_AVAILABLE, isRootAvailable).apply()
+
     var enableRootAccess: Boolean
         get() = prefs.getBoolean(ENABLE_ROOT_ACCESS, false)
         set(enableRootAccess) = prefs.edit().putBoolean(ENABLE_ROOT_ACCESS, enableRootAccess).apply()

app/src/main/kotlin/com/simplemobiletools/filemanager/Constants.kt

@@ -10,4 +10,5 @@ val FAVORITES = "favorites"
 val SORT_ORDER = "sort_order"
 val SORT_FOLDER_PREFIX = "sort_folder_"
 val TEMPORARILY_SHOW_HIDDEN = "temporarily_show_hidden"
+val IS_ROOT_AVAILABLE = "is_root_available"
 val ENABLE_ROOT_ACCESS = "enable_root_access"

app/src/main/kotlin/com/simplemobiletools/filemanager/activities/MainActivity.kt

@@ -25,6 +25,7 @@ import com.simplemobiletools.filemanager.SCROLL_STATE
 import com.simplemobiletools.filemanager.dialogs.ChangeSortingDialog
 import com.simplemobiletools.filemanager.extensions.config
 import com.simplemobiletools.filemanager.fragments.ItemsFragment
+import com.stericson.RootTools.RootTools
 import kotlinx.android.synthetic.main.activity_main.*
 import java.util.*
 
@@ -45,6 +46,7 @@ class MainActivity : SimpleActivity(), ItemsFragment.ItemInteractionListener, Br
         tryInitFileManager()
         storeStoragePaths()
         checkWhatsNewDialog()
+        checkIfRootAvailable()
     }
 
     override fun onResume() {
@@ -246,6 +248,12 @@ class MainActivity : SimpleActivity(), ItemsFragment.ItemInteractionListener, Br
         }
     }
 
+    private fun checkIfRootAvailable() {
+        Thread({
+            config.isRootAvailable = RootTools.isRootAvailable()
+        }).start()
+    }
+
     private fun checkWhatsNewDialog() {
         arrayListOf<Release>().apply {
             add(Release(26, R.string.release_26))

app/src/main/kotlin/com/simplemobiletools/filemanager/activities/SettingsActivity.kt

@@ -3,6 +3,7 @@ package com.simplemobiletools.filemanager.activities
 import android.content.Intent
 import android.os.Bundle
 import com.simplemobiletools.commons.dialogs.SecurityDialog
+import com.simplemobiletools.commons.extensions.beVisibleIf
 import com.simplemobiletools.commons.extensions.handleHiddenFolderPasswordProtection
 import com.simplemobiletools.commons.extensions.updateTextColors
 import com.simplemobiletools.commons.helpers.SHOW_ALL_TABS
@@ -73,6 +74,7 @@ class SettingsActivity : SimpleActivity() {
     }
 
     private fun setupEnableRootAccess() {
+        settings_enable_root_access_holder.beVisibleIf(config.isRootAvailable)
         settings_enable_root_access.isChecked = config.enableRootAccess
         settings_enable_root_access_holder.setOnClickListener {
             if (!config.enableRootAccess) {