Shows prompt when Bluetooth is off and trying to add device

When trying to add a Meshtastic device, the app will check if bluetooth is turned on, if it isn't then it will display a message.

app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt

@@ -1,5 +1,6 @@
 package com.geeksville.mesh.ui
 
+import android.bluetooth.BluetoothAdapter
 import android.bluetooth.BluetoothDevice
 import android.companion.CompanionDeviceManager
 import android.content.*
@@ -475,6 +476,7 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
             if (!myActivity.hasScanPermission()) {
                 myActivity.requestScanPermission()
             } else {
+                checkBTEnabled()
                 if (!scanModel.hasCompanionDeviceApi) checkLocationEnabled()
                 scanLeDevice()
             }
@@ -501,6 +503,18 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
         }
     }
 
+    private fun checkBTEnabled(
+        warningReason: String = getString(R.string.requires_bluetooth)
+    ) {
+
+        var btAdapter = BluetoothAdapter.getDefaultAdapter();
+
+        if (!(btAdapter.isEnabled())) {
+            warn("We need bluetooth")
+            showSnackbar(warningReason)
+        }
+    }
+
     private val updateProgressFilter = IntentFilter(SoftwareUpdateService.ACTION_UPDATE_PROGRESS)
 
     private val updateProgressReceiver: BroadcastReceiver = object : BroadcastReceiver() {