Android 部分 1.繼承 webviewClient and override OnReceiveError method 2.Custom Render the WebView iOS 部分 1.繼承 WKWebview and override decidePolicyForNavigationResponse method 2.Custom Render the WebView 收到ErrorCode再發EventAggregator 或 MessagingCenter 觸發上層Root Page再轉發Error Page 參考來源 : https://docs.microsoft.com/zh-tw/xamarin/xamarin-forms/app-fundamentals/custom-renderer/hybridwebview
