[webview_flutter_wkwebview] Updates platform views on iOS to only have a weak reference to the native view

packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.24.1
+
+* Updates platform views on iOS to only have a weak reference to the native view. This is a
+  potential workaround to prevent a crash during the Flutter engine shutdown. See https://github.com/flutter/flutter/issues/168535
+
 ## 3.24.0
 
 * Adds support for `WebKitWebViewControllerCreationParams.javaScriptCanOpenWindowsAutomatically` to allow JavaScript's

packages/webview_flutter/webview_flutter_wkwebview/darwin/Tests/PlatformViewImplTests.swift

@@ -0,0 +1,25 @@
+// Copyright 2013 The Flutter Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import XCTest
+
+@testable import webview_flutter_wkwebview
+
+#if os(iOS)
+  import UIKit
+#endif
+
+class PlatformViewImplTests: XCTestCase {
+  #if os(iOS)
+    func testPlatformViewImplStoresViewWithAWeakReference() {
+      var view: UIView? = UIView()
+      let platformView = PlatformViewImpl(uiView: view!)
+
+      XCTAssertNotNil(platformView.uiView)
+
+      view = nil
+      XCTAssertNil(platformView.uiView)
+    }
+  #endif
+}

packages/webview_flutter/webview_flutter_wkwebview/darwin/webview_flutter_wkwebview/Sources/webview_flutter_wkwebview/FlutterViewFactory.swift

@@ -13,23 +13,36 @@ import Foundation
   #error("Unsupported platform.")
 #endif
 
-/// Implementation of `FlutterPlatformViewFactory` that retrieves the view from the `WebKitLibraryPigeonInstanceManager`.
-class FlutterViewFactory: NSObject, FlutterPlatformViewFactory {
-  unowned let instanceManager: WebKitLibraryPigeonInstanceManager
-
-  #if os(iOS)
-    class PlatformViewImpl: NSObject, FlutterPlatformView {
-      let uiView: UIView
+#if os(iOS)
+  class PlatformViewImpl: NSObject, FlutterPlatformView {
+    // TODO(bparrishMines): Change to strong reference once this issue is fixed in the engine and
+    // makes it to stable. See https://github.com/flutter/flutter/issues/168535.
+    // The InstanceManager used by pigeon adds an associated object to added instances that makes a message call when
+    // they are deallocated. This sets a weak reference to the underlying UIView to prevent a crash where the UIView is
+    // no longer referenced by the plugin, but the FlutterViewController still maintains a transitive reference to it
+    // when the BinaryMessenger becomes invalid.
+    weak var uiView: UIView?
 
-      init(uiView: UIView) {
-        self.uiView = uiView
-      }
+    init(uiView: UIView) {
+      self.uiView = uiView
+    }
 
-      func view() -> UIView {
+    func view() -> UIView {
+      if let uiView = uiView {
         return uiView
       }
+
+      NSLog(
+        "WebViewFlutterPluginError: UIView has been deallocated, but is still being requested as a PlatformView."
+      )
+      return UIView()
     }
-  #endif
+  }
+#endif
+
+/// Implementation of `FlutterPlatformViewFactory` that retrieves the view from the `WebKitLibraryPigeonInstanceManager`.
+class FlutterViewFactory: NSObject, FlutterPlatformViewFactory {
+  unowned let instanceManager: WebKitLibraryPigeonInstanceManager
 
   init(instanceManager: WebKitLibraryPigeonInstanceManager) {
     self.instanceManager = instanceManager
@@ -42,14 +55,9 @@ class FlutterViewFactory: NSObject, FlutterPlatformViewFactory {
       let identifier: Int64 = args is Int64 ? args as! Int64 : Int64(args as! Int32)
       let instance: AnyObject? = instanceManager.instance(forIdentifier: identifier)
 
-      if let instance = instance as? FlutterPlatformView {
-        instance.view().frame = frame
-        return instance
-      } else {
-        let view = instance as! UIView
-        view.frame = frame
-        return PlatformViewImpl(uiView: view)
-      }
+      let view = instance as! UIView
+      view.frame = frame
+      return PlatformViewImpl(uiView: view)
     }
   #elseif os(macOS)
     func create(

packages/webview_flutter/webview_flutter_wkwebview/pubspec.yaml

@@ -2,7 +2,7 @@ name: webview_flutter_wkwebview
 description: A Flutter plugin that provides a WebView widget based on Apple's WKWebView control.
 repository: https://github.com/flutter/packages/tree/main/packages/webview_flutter/webview_flutter_wkwebview
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+webview%22
-version: 3.24.0
+version: 3.24.1
 
 environment:
   sdk: ^3.9.0