Fix FlutterBlue.state stream cancel

CHANGELOG.md

@@ -2,6 +2,7 @@
 * connect timeout fixed (thanks to crazy-rodney, sophisticode, SkuggaEdward, MousyBusiness and cthurston)
 * Add timestamp field to ScanResult class #59 (thanks to simon-iversen)
 * Add FlutterBlue.name to get the human readable device name #93 (thanks to mvo5)
+* Fix bug where if there were multiple subscribers to FlutterBlue.state and one cancelled it would accidentally cancel all subscribers (thank to MacMalainey and MrCsabaToth)
 
 ## 1.1.3
 * Read RSSI from a connected BLE device #1 (thanks to sophisticode)

lib/src/flutter_blue_plus.dart

@@ -14,6 +14,12 @@ class FlutterBluePlus {
  Stream<MethodCall> get _methodStream => _methodStreamController
  .stream; // Used internally to dispatch methods from platform.
 
+ /// Cached broadcast stream for FlutterBlue.state events
+ /// Caching this stream allows for more than one listener to subscribe
+ /// and unsubscribe apart from each other,
+ /// while allowing events to still be sent to others that are subscribed
+ Stream<BluetoothState>? _stateStream;
+
  /// Singleton boilerplate
  FlutterBluePlus._() {
  _channel.setMethodCallHandler((MethodCall call) async {
@@ -87,10 +93,13 @@ class FlutterBluePlus {
  .then((buffer) => protos.BluetoothState.fromBuffer(buffer))
  .then((s) => BluetoothState.values[s.state.value]);
 
- yield* _stateChannel
+ _stateStream ??= _stateChannel
  .receiveBroadcastStream()
  .map((buffer) => protos.BluetoothState.fromBuffer(buffer))
- .map((s) => BluetoothState.values[s.state.value]);
+ .map((s) => BluetoothState.values[s.state.value])
+ .doOnCancel(() => _stateStream = null);
+
+ yield* _stateStream!;
  }
 
  /// Retrieve a list of connected devices