Windows商店应用程序:通过代码动态更改背景图像

Question

我在一个天气应用程序上工作，我想根据天气的晴朗，多云等动态改变背景图像。我将来自App.xaml.cs的所有页面的背景图像设置如下：

  rootFrame.Background = new ImageBrush
            {
                Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill,
                ImageSource = new BitmapImage { UriSource = new Uri("ms-appx:///Assets/blueSky.jpg") }
            };

我在App.xaml.cs中设置了图像，这样所有页面都会得到相同的图像，而不需要每次都加载图像。App.xaml.cs的完整代码：

 sealed partial class App : Application
{

    /// <summary>
    /// Initializes the singleton application object.  This is the first line of authored code
    /// executed, and as such is the logical equivalent of main() or WinMain().
    /// </summary>
    public App()
    {
        this.InitializeComponent();
        this.Suspending += OnSuspending;

    }

    /// <summary>
    /// Invoked when the application is launched normally by the end user.  Other entry points
    /// will be used when the application is launched to open a specific file, to display
    /// search results, and so forth.
    /// </summary>
    /// <param name="args">Details about the launch request and process.</param>
    protected async override void OnLaunched(LaunchActivatedEventArgs args)
    {
        Frame rootFrame = Window.Current.Content as Frame;


        // Do not repeat app initialization when the Window already has content,
        // just ensure that the window is active
        if (rootFrame == null)
        {
            // Create a Frame to act as the navigation context and navigate to the first page
            rootFrame = new Frame();


            // Her we set the application background Image for all pages
            rootFrame.Background = new ImageBrush
            {
                Stretch = Windows.UI.Xaml.Media.Stretch.UniformToFill,
                ImageSource = new BitmapImage { UriSource = new Uri("ms-appx:///Assets/blueSky.jpg") }
            };
            weather.Common.SuspensionManager.RegisterFrame(rootFrame, "appFrame");


            if (args.PreviousExecutionState == ApplicationExecutionState.Terminated)
            {
                //TODO: Load state from previously suspended application
                await weather.Common.SuspensionManager.RestoreAsync();
            }

            // Place the frame in the current Window
            Window.Current.Content = rootFrame;
        }

        if (rootFrame.Content == null)
        {
            // When the navigation stack isn't restored navigate to the first page,
            // configuring the new page by passing required information as a navigation
            // parameter
            if (!rootFrame.Navigate(typeof(MainPage), args.Arguments))
            {
                throw new Exception("Failed to create initial page");
            }
        }
        // Ensure the current window is active
        Window.Current.Activate();
    }

    /// <summary>
    /// Invoked when application execution is being suspended.  Application state is saved
    /// without knowing whether the application will be terminated or resumed with the contents
    /// of memory still intact.
    /// </summary>
    /// <param name="sender">The source of the suspend request.</param>
    /// <param name="e">Details about the suspend request.</param>
    private async void OnSuspending(object sender, SuspendingEventArgs e)
    {
        var deferral = e.SuspendingOperation.GetDeferral();
        //TODO: Save application state and stop any background activity
        await weather.Common.SuspensionManager.SaveAsync();
        deferral.Complete();
    }
}

这对于1张图像很好，但我不能自动更改图像。有什么想法吗？

Answer 1

从web服务获取天气信息的代码在哪里？在该代码中，获取当前天气，然后根据天气预报设置背景图片。