在App构造函数中调用此方法（在设置MainPage之前）

private void SetUpEntry()
    {
        Microsoft.Maui.Handlers.EntryHandler.Mapper.AppendToMapping("SetUpEntry", (handler, view) =>
        {
#if ANDROID

#elif IOS || MACCATALYST

            //remove outline
            handler.PlatformView.BorderStyle = UIKit.UITextBorderStyle.None;

#elif WINDOWS
      
#endif
        });
    }