Fix crash when closing a window with Alt+F4 in multi-win Flutter on Windows

shell/platform/windows/flutter_windows_view.cc

@@ -536,12 +536,15 @@ void FlutterWindowsView::SendKey(int key,
                                  KeyEventCallback callback) {
   engine_->keyboard_key_handler()->KeyboardHook(
       key, scancode, action, character, extended, was_down,
-      [=, callback = std::move(callback)](bool handled) {
-        if (!handled) {
-          engine_->text_input_plugin()->KeyboardHook(
-              key, scancode, action, character, extended, was_down);
+      [=, engine = engine_, view_id = view_id_,
+       callback = std::move(callback)](bool handled) {
+        if (engine->view(view_id)) {
+          if (!handled) {
+            engine->text_input_plugin()->KeyboardHook(
+                key, scancode, action, character, extended, was_down);
+          }
+          callback(handled);
         }
-        callback(handled);
       });
 }
 

shell/platform/windows/flutter_windows_view_unittests.cc

@@ -306,6 +306,35 @@ TEST(FlutterWindowsViewTest, KeySequence) {
   key_event_logs.clear();
 }
 
+TEST(FlutterWindowsViewTest, KeyEventCallback) {
+  std::unique_ptr<FlutterWindowsEngine> engine = GetTestEngine();
+
+  std::unique_ptr<FlutterWindowsView> view = engine->CreateView(
+      std::make_unique<NiceMock<MockWindowBindingHandler>>());
+
+  class MockCallback {
+   public:
+    MOCK_METHOD(void, Call, ());
+  };
+
+  NiceMock<MockCallback> callback_with_valid_view;
+  NiceMock<MockCallback> callback_with_invalid_view;
+
+  auto trigger_key_event = [&](NiceMock<MockCallback>& callback) {
+    view->OnKey(kVirtualKeyA, kScanCodeKeyA, WM_KEYDOWN, 'a', false, false,
+                [&](bool) { callback.Call(); });
+  };
+
+  EXPECT_CALL(callback_with_valid_view, Call()).Times(1);
+  EXPECT_CALL(callback_with_invalid_view, Call()).Times(0);
+
+  trigger_key_event(callback_with_valid_view);
+  engine->RemoveView(view->view_id());
+  trigger_key_event(callback_with_invalid_view);
+
+  key_event_logs.clear();
+}
+
 TEST(FlutterWindowsViewTest, EnableSemantics) {
   std::unique_ptr<FlutterWindowsEngine> engine = GetTestEngine();
   EngineModifier modifier(engine.get());