automatically detect subscription type

automatically detect subscription type on Android so that
isNotification param doesn’t need to be specified

Author: randdusing

readme.md

@@ -957,7 +957,7 @@ bluetoothle.read(readSuccess, readError, params);
 
 
 ### subscribe ###
-Subscribe to a particular service's characteristic. Once a subscription is no longer needed, execute unsubscribe in a similar fashion. The Client Configuration descriptor will automatically be written to enable notification/indication.
+Subscribe to a particular service's characteristic. Once a subscription is no longer needed, execute unsubscribe in a similar fashion. The Client Configuration descriptor will automatically be written to enable notification/indication based on the characteristic's properties.
 
 ```javascript
 bluetoothle.subscribe(subscribeSuccess, subscribeError, params);
@@ -967,14 +967,12 @@ bluetoothle.subscribe(subscribeSuccess, subscribeError, params);
 * address = The address/identifier provided by the scan's return object
 * service = The service's UUID
 * characteristic = The characteristic's UUID
-* isNotification is only required on Android. True (or null) means notification will be enabled. False means indication will be enabled.
 
 ```javascript
 {
   "address": "ECC037FD-72AE-AFC5-9213-CA785B3B5C63",
   "service": "180d",
   "characteristic": "2a37",
-  "isNotification" : true
 }
 ```
 

src/android/BluetoothLePlugin.java

@@ -148,7 +148,6 @@ public class BluetoothLePlugin extends CordovaPlugin {
   private final String keyIsScanning = "isScanning";
   private final String keyIsConnected = "isConnected";
   private final String keyIsDiscovered = "isDiscovered";
-  private final String keyIsNotification = "isNotification";
   private final String keyPeripheral = "peripheral";
   private final String keyState = "state";
   private final String keyDiscoveredState = "discoveredState";
@@ -1794,11 +1793,10 @@ private void subscribeAction(JSONArray args, CallbackContext callbackContext) {
 
     boolean result = false;
 
-    //Set the descriptor for notification
-    if (obj.optBoolean(keyIsNotification, true)) {
+    //Use properties to determine whether notification or indication should be used
+    if ((characteristic.getProperties() & BluetoothGattCharacteristic.PROPERTY_NOTIFY) == BluetoothGattCharacteristic.PROPERTY_NOTIFY) {
       result = descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
     } else {
-      //Or for indication
       result = descriptor.setValue(BluetoothGattDescriptor.ENABLE_INDICATION_VALUE);
     }