Add isDiscoverable to detect is discoverable mode active

- Remove `getDiscoverableTimeout` since it was not working properly (almost always returning last set timeout)
+ Add example with countdown for discoverable mode timeout

android/src/main/java/io/github/edufolly/flutterbluetoothserial/FlutterBluetoothSerialPlugin.java

@@ -359,18 +359,9 @@ public void onResult(boolean granted) {
                 result.success(null);
                 break;
 
-            case "getDiscoverableTimeout": {
-                try {
-                    java.lang.reflect.Method method;
-                    method = bluetoothAdapter.getClass().getMethod("getDiscoverableTimeout");
-                    int value = (int) method.invoke(bluetoothAdapter);
-                    result.success(value);
-                }
-                catch (Exception ex) {
-                    result.error("bond_error", "error while unbonding", exceptionToString(ex));
-                }
+            case "isDiscoverable":
+                result.success(bluetoothAdapter.getScanMode() == BluetoothAdapter.SCAN_MODE_CONNECTABLE_DISCOVERABLE);
                 break;
-            }
 
             case "requestDiscoverable": {
                 Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);

example/lib/MainPage.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
 import 'package:scoped_model/scoped_model.dart';
@@ -18,6 +19,9 @@ class MainPage extends StatefulWidget {
 class _MainPage extends State<MainPage> {
   BluetoothState _bluetoothState = BluetoothState.UNKNOWN;
 
+  Timer _discoverableTimeoutTimer;
+  int _discoverableTimeoutSecondsLeft = 0;
+
   BackgroundCollectingTask _collectingTask;
 
   @override
@@ -31,13 +35,20 @@ class _MainPage extends State<MainPage> {
 
     // Listen for futher state changes
     FlutterBluetoothSerial.instance.onStateChanged().listen((BluetoothState state) {
-      setState(() { _bluetoothState = state; });
+      setState(() {
+        _bluetoothState = state;
+
+        // Discoverable mode is disabled when Bluetooth gets disabled
+        _discoverableTimeoutTimer = null;
+        _discoverableTimeoutSecondsLeft = 0;
+      });
     });
   }
 
   @override
   void dispose() {
     _collectingTask?.dispose();
+    _discoverableTimeoutTimer?.cancel();
     super.dispose();
   }
 
@@ -81,7 +92,7 @@ class _MainPage extends State<MainPage> {
               ),
             ),
             ListTile(
-              title: Text("Discoverable"),
+              title: _discoverableTimeoutSecondsLeft == 0 ? const Text("Discoverable") : Text("Discoverable for $_discoverableTimeoutSecondsLeft seconds"),
               subtitle: const Text("PsychoX-Luna"),
               trailing: Row(
                 mainAxisSize: MainAxisSize.min,
@@ -101,6 +112,21 @@ class _MainPage extends State<MainPage> {
                       else {
                         print('Discoverable mode acquired for $timeout seconds');
                       }
+                      setState(() {
+                        _discoverableTimeoutTimer?.cancel();
+                        _discoverableTimeoutSecondsLeft = timeout;
+                        _discoverableTimeoutTimer = Timer.periodic(Duration(seconds: 1), (Timer timer) {
+                          setState(() {
+                            if (_discoverableTimeoutSecondsLeft <= 0) {
+                              timer.cancel();
+                              _discoverableTimeoutSecondsLeft = 0;
+                            }
+                            else {
+                              _discoverableTimeoutSecondsLeft -= 1;
+                            }
+                          });
+                        });
+                      });
                     },
                   )
                 ]

lib/FlutterBluetoothSerial.dart

@@ -90,9 +90,8 @@ class FlutterBluetoothSerial {
 
   // @TODO . add `discoverableName` (get/set)
 
-  /// Timeout in seconds left in discoverable mode. Negative values means 
-  /// out of discoverable mode or error (such as adapter disabled).
-  Future<int> get discoverableTimeout => _methodChannel.invokeMethod("getDiscoverableTimeout");
+  /// Describes is the local device in discoverable mode.
+  Future<bool> get isDiscoverable => _methodChannel.invokeMethod("isDiscoverable");
 
   /// Asks for discoverable mode (probably always prompt for user interaction in fact).
   /// Returns number of seconds acquired or zero if canceled or failed gracefully.