[webview_flutter_wkwebview] add functions to display a system popup using Javascript in iOS

packages/webview_flutter/webview_flutter_wkwebview/ios/Classes/FWFUIDelegateHostApi.m

@@ -133,6 +133,62 @@ - (void)webView:(WKWebView *)webView
                                                     decisionHandler(decision);
                                                   }];
 }
+
+- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler {
+    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"" message:message preferredStyle:UIAlertControllerStyleAlert];
+      [alert addAction:[UIAlertAction actionWithTitle:@"Ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
+        completionHandler();
+      }]];
+      [[self topViewController] presentViewController:alert animated:YES completion:NULL];
+}
+
+- (void)webView:(WKWebView *)webView runJavaScriptConfirmPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(BOOL))completionHandler {
+    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"" message:message preferredStyle:UIAlertControllerStyleAlert];
+      [alert addAction:[UIAlertAction actionWithTitle:@"Ok" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
+        completionHandler(YES);
+      }]];
+      [alert addAction:[UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction *action) {
+        completionHandler(NO);
+      }]];
+      [[self topViewController] presentViewController:alert animated:YES completion:NULL];
+    completionHandler(true);
+}
+
+-(UIViewController *)topViewController{
+    UIViewController *controller = [self topViewControllerWithRootViewController:[self getCurrentWindow].rootViewController];
+    return controller;
+}
+
+/**
+ * topViewControllerWithRootViewController
+ */
+-(UIViewController *)topViewControllerWithRootViewController:(UIViewController *)viewController{
+  if (viewController==nil) return nil;
+  if (viewController.presentedViewController!=nil) {
+    return [self topViewControllerWithRootViewController:viewController.presentedViewController];
+  } else if ([viewController isKindOfClass:[UITabBarController class]]){
+    return [self topViewControllerWithRootViewController:[(UITabBarController *)viewController selectedViewController]];
+  } else if ([viewController isKindOfClass:[UINavigationController class]]){
+    return [self topViewControllerWithRootViewController:[(UINavigationController *)viewController visibleViewController]];
+  } else {
+    return viewController;
+  }
+}
+/**
+ * getCurrentWindow
+ */
+-(UIWindow *)getCurrentWindow{
+  UIWindow *window = [UIApplication sharedApplication].keyWindow;
+  if (window.windowLevel!=UIWindowLevelNormal) {
+    for (UIWindow *wid in [UIApplication sharedApplication].windows) {
+      if (window.windowLevel==UIWindowLevelNormal) {
+        window = wid;
+        break;
+      }
+    }
+  }
+  return window;
+}
 @end
 
 @interface FWFUIDelegateHostApiImpl ()
@@ -164,4 +220,6 @@ - (void)createWithIdentifier:(nonnull NSNumber *)identifier
                                                              instanceManager:self.instanceManager];
   [self.instanceManager addDartCreatedInstance:uIDelegate withIdentifier:identifier.longValue];
 }
+
+
 @end