XML : Android - check for loss of Bluetooth connection?

I am writing an app that connects to an Arduino bluetooth device. The goal is for the Android user to receive a push notification if the phone leaves the range of the Arduino. This should occur regardless of whether the app is in the foreground or not. To do this, I am currently using a BroadcastReceiver in the Android Manifest. However, I am not receiving any such notifications.

Here is the Receiver class that implements BroadcastReceiver:

  public class Receiver extends BroadcastReceiver {        @Override      public void onReceive(Context context, Intent intent) {          BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();          String action = intent.getAction();          if (action.equals(BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED)) {              if (adapter.getState() == BluetoothAdapter.STATE_OFF) {                  pushNotification(context);              }          }      }        public void pushNotification(Context context) {            NotificationCompat.Builder builder = new NotificationCompat.Builder(context);          builder.setSmallIcon(R.mipmap.ic_launcher);            builder.setAutoCancel(true);            builder.setLargeIcon(BitmapFactory.decodeResource(context.getResources(), R.mipmap.ic_launcher));            builder.setContentTitle("This is a notification!");          builder.setContentText("This is the notification text!");          builder.setSubText("This is the notification subtext!");            NotificationManager notificationManager = (NotificationManager) context.getSystemService(context.NOTIFICATION_SERVICE);          notificationManager.notify(1, builder.build());      }  }    

And the AndroidManifest.xml

  <?xml version="1.0" encoding="utf-8"?>  <manifest xmlns:android="http://schemas.android.com/apk/res/android">        <uses-permission android:name="android.permission.BLUETOOTH"/>      <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>      <uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>        <application          android:allowBackup="true"          android:icon="@mipmap/ic_launcher"          android:label="@string/app_name"          android:supportsRtl="true"          android:theme="@style/AppTheme">          <activity android:name=".MainActivity">              <intent-filter>                  <action android:name="android.intent.action.MAIN" />                    <category android:name="android.intent.category.LAUNCHER" />              </intent-filter>          </activity>          <receiver              android:name=".Receiver"              android:enabled="true"              android:exported="true">              <intent-filter>                  <action android:name="android.bluetooth.adapter.action.STATE_CHANGED" />              </intent-filter>          </receiver>      </application>    </manifest>    

I'm fairly certain that the problem lies in the constants I am using in my logic. However, I'm not sure which ones I should use. As it is, the receiver is activated when ANY state change occurs to the Android Bluetooth, but I only want a notification when the connection is lost, which might not have anything to do with a state change of the Android Bluetooth receiver. What should I do to make sure pushNotification() is called under these conditions?