🐛 Construct listener gracefully

lib/src/fluwx.dart

@@ -25,21 +25,22 @@ import 'method_channel/fluwx_platform_interface.dart';
 import 'response/wechat_response.dart';
 
 class Fluwx {
-  late final WeakReference<void Function(WeChatResponse event)>
-      responseListener;
+  Fluwx() {
+    _responseSubscription = FluwxPlatform.instance.responseEventHandler.listen(
+      _responseEventListener,
+      onDone: () {
+        _responseSubscription?.cancel();
+      },
+    );
+  }
 
-  final List<WeChatResponseSubscriber> _responseListeners = [];
+  final _responseListeners = <WeChatResponseSubscriber>[];
+  StreamSubscription? _responseSubscription;
 
-  Fluwx() {
-    responseListener = WeakReference((event) {
-      for (var listener in _responseListeners) {
+  void _responseEventListener(WeChatResponse event) {
+    for (final listener in _responseListeners.toList()) {
       listener(event);
     }
-    });
-    final target = responseListener.target;
-    if (target != null) {
-      FluwxPlatform.instance.responseEventHandler.listen(target);
-    }
   }
 
   Future<bool> get isWeChatInstalled =>