关于加载图片问题w

Question

我想在程序运行的时候提前把mainpage的image1控件图片加载完毕再进入，但是图片却不显示

 private void Application_Launching(object sender, LaunchingEventArgs e)
        {
            MainPage main = new MainPage();
            BitmapImage bi = new BitmapImage(new Uri("startscreen2.jpg", UriKind.RelativeOrAbsolute));
            main.image1.Source = bi;
            System.Threading.Thread.Sleep(4000);
          }