[FSSDK-12503] fix: guard static MethodChannel from multi-engine overwrite

android/src/main/java/com/optimizely/optimizely_flutter_sdk/FlutterLogbackAppender.java

@@ -14,11 +14,17 @@
 public class FlutterLogbackAppender extends AppenderBase<ILoggingEvent> {
 
     public static final String CHANNEL_NAME = "optimizely_flutter_sdk_logger";
-    public static MethodChannel channel;
+    private static MethodChannel channel;
     private static final Handler mainThreadHandler = new Handler(Looper.getMainLooper());
 
-    public static void setChannel(MethodChannel channel) {
-        FlutterLogbackAppender.channel = channel;
+    public static void setChannel(MethodChannel newChannel) {
+        if (channel == null) {
+            channel = newChannel;
+        }
+    }
+
+    public static void clearChannel() {
+        channel = null;
     }
 
     @Override

android/src/main/java/com/optimizely/optimizely_flutter_sdk/OptimizelyFlutterSdkPlugin.java

@@ -212,6 +212,9 @@ public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
 
   @Override
   public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
+    if (channel != null) {
+      return;
+    }
     channel = new MethodChannel(binding.getBinaryMessenger(), "optimizely_flutter_sdk");
     channel.setMethodCallHandler(this);
     context = binding.getApplicationContext();
@@ -232,15 +235,16 @@ public void onAttachedToEngine(@NonNull FlutterPluginBinding binding) {
   @Override
   public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
     channel.setMethodCallHandler(null);
+    channel = null;
     // Stop and detach the appender
     if (flutterLogbackAppender != null) {
         Logger rootLogger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME);
         rootLogger.detachAppender(flutterLogbackAppender);
         flutterLogbackAppender.stop();
         flutterLogbackAppender = null;
     }
-    // Clean up the channel
-    FlutterLogbackAppender.setChannel(null);
+    // Clean up the logger channel
+    FlutterLogbackAppender.clearChannel();
   }
 
   @Override

ios/Classes/OptimizelyFlutterLogger.swift

@@ -13,7 +13,13 @@ public class OptimizelyFlutterLogger: NSObject, OPTLogger {
     }
 
     public static func setChannel(_ channel: FlutterMethodChannel) {
-        loggerChannel = channel
+        if loggerChannel == nil {
+            loggerChannel = channel
+        }
+    }
+
+    public static func clearChannel() {
+        loggerChannel = nil
     }
 
     public func log(level: OptimizelyLogLevel, message: String) {

ios/Classes/SwiftOptimizelyFlutterSdkPlugin.swift

@@ -38,6 +38,9 @@ public class SwiftOptimizelyFlutterSdkPlugin: NSObject, FlutterPlugin {
 
     /// Registers optimizely_flutter_sdk channel to communicate with the flutter sdk to receive requests and send responses
     public static func register(with registrar: FlutterPluginRegistrar) {
+        if channel != nil {
+            return
+        }
         channel = FlutterMethodChannel(name: "optimizely_flutter_sdk", binaryMessenger: registrar.messenger())
         let instance = SwiftOptimizelyFlutterSdkPlugin()
         registrar.addMethodCallDelegate(instance, channel: channel)
@@ -50,7 +53,13 @@ public class SwiftOptimizelyFlutterSdkPlugin: NSObject, FlutterPlugin {
                                                 taskQueue: taskQueue)
         OptimizelyFlutterLogger.setChannel(loggerChannel)
     }
-
+
+    public func detachFromEngine(for registrar: FlutterPluginRegistrar) {
+        Self.channel?.setMethodCallHandler(nil)
+        Self.channel = nil
+        OptimizelyFlutterLogger.clearChannel()
+    }
+
     /// Part of FlutterPlugin protocol to handle communication with flutter sdk.
     /// All method handlers receive a main-thread-safe result callback so that
     /// any handler calling result() from a background thread (e.g. async SDK