Fix RCTAlertController not showing when using SceneDelegate on iOS 13.0+ (#35716)

Summary:
On iOS 13.0+, app may use SceneDelegate for multiple windows support or CarPlay support. RCTAlertController can't find the correct root vc in such scene based apps.

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[iOS] [Fixed] - Fix RCTAlertController not showing when using SceneDelegate on iOS 13.0+.

Pull Request resolved: #35716

Reviewed By: cipolleschi

Differential Revision: D42253653

Pulled By: makovkastar

fbshipit-source-id: ae4e833abca2af7af8028f3af9bd8d3f60ebd392

Author: ouabing

React/CoreModules/RCTAlertController.m

@@ -20,14 +20,21 @@ @implementation RCTAlertController
 - (UIWindow *)alertWindow
 {
   if (_alertWindow == nil) {
-    UIWindow *keyWindow = RCTSharedApplication().keyWindow;
-    if (keyWindow) {
-      _alertWindow = [[UIWindow alloc] initWithFrame:keyWindow.bounds];
+    _alertWindow = [self getUIWindowFromScene];
+
+    if (_alertWindow == nil) {
+      UIWindow *keyWindow = RCTSharedApplication().keyWindow;
+      if (keyWindow) {
+        _alertWindow = [[UIWindow alloc] initWithFrame:keyWindow.bounds];
+      } else {
+        // keyWindow is nil, so we cannot create and initialize _alertWindow
+        NSLog(@"Unable to create alert window: keyWindow is nil");
+      }
+    }
+
+    if (_alertWindow) {
       _alertWindow.rootViewController = [UIViewController new];
       _alertWindow.windowLevel = UIWindowLevelAlert + 1;
-    } else {
-      // keyWindow is nil, so we cannot create and initialize _alertWindow
-      NSLog(@"Unable to create alert window: keyWindow is nil");
     }
   }
 
@@ -56,4 +63,17 @@ - (void)hide
   _alertWindow = nil;
 }
 
+- (UIWindow *)getUIWindowFromScene
+{
+  if (@available(iOS 13.0, *)) {
+    for (UIScene *scene in RCTSharedApplication().connectedScenes) {
+      if (scene.activationState == UISceneActivationStateForegroundActive &&
+          [scene isKindOfClass:[UIWindowScene class]]) {
+        return [[UIWindow alloc] initWithWindowScene:(UIWindowScene *)scene];
+      }
+    }
+  }
+  return nil;
+}
+
 @end