我想知道在墓碑之后是否有办法将页面状态恢复到应用程序中的标准页面。例如，如果应用程序在用户位于第2页时进行了逻辑删除，则还原的页面将始终为页面1.我在如何从应用程序的第2页恢复数据时遇到问题，我将此方法视为克服此问题的替代方法问题
public FeedPage()
{
InitializeComponent();
this.Loaded += new RoutedEventHandler(FeedPage_Loaded);
performanceProgressBar.Visibility = System.Windows.Visibility.Collapsed;
LoadFeed();
}
private void LoadFeed()
{
FrameworkElement root = Application.Current.RootVisual as FrameworkElement;
var currentFeed = root.DataContext as FeedViewModel;
WebClient client = new WebClient();
performanceProgressBar.IsIndeterminate = true;
performanceProgressBar.Visibility = System.Windows.Visibility.Visible;
client.DownloadStringCompleted += new DownloadStringCompletedEventHandler(client_DownloadStringCompleted);
client.DownloadStringAsync(new Uri(currentFeed.FeedUrl));
this.DataContext = currentFeed;
ApplicationBar.IsVisible = false;
}
...
private void FeedPage_Loaded(object sender, RoutedEventArgs e)
{
if (!App.ViewModel.IsDataLoaded)
{
App.ViewModel.LoadData();
}
}
我的问题是我现在不知道如何在tobstone存储currentFeed。每次激活应用程序时，currentFeed都为空。我尝试了很多解决方案但没有结果。
public partial class App : Application
{
private static MainViewModel viewModel = null;
/// <summary>
/// A static ViewModel used by the views to bind against.
/// </summary>
/// <returns>The MainViewModel object.</returns>
public static MainViewModel ViewModel
{
get
{
// Delay creation of the view model until necessary
if (viewModel == null)
viewModel = new MainViewModel();
return viewModel;
}
}
/// <summary>
/// Provides easy access to the root frame of the Phone Application.
/// </summary>
/// <returns>The root frame of the Phone Application.</returns>
public PhoneApplicationFrame RootFrame { get; private set; }
/// <summary>
/// Constructor for the Application object.
/// </summary>
public App()
{
// Global handler for uncaught exceptions.
UnhandledException += Application_UnhandledException;
// Show graphics profiling information while debugging.
if (System.Diagnostics.Debugger.IsAttached)
{
// Display the current frame rate counters.
Application.Current.Host.Settings.EnableFrameRateCounter = true;
// Show the areas of the app that are being redrawn in each frame.
//Application.Current.Host.Settings.EnableRedrawRegions = true;
// Enable non-production analysis visualization mode,
// which shows areas of a page that are being GPU accelerated with a colored overlay.
//Application.Current.Host.Settings.EnableCacheVisualization = true;
}
// Standard Silverlight initialization
InitializeComponent();
// Phone-specific initialization
InitializePhoneApplication();
}
// Code to execute when the application is launching (eg, from Start)
// This code will not execute when the application is reactivated
private void Application_Launching(object sender, LaunchingEventArgs e)
{
}
// Code to execute when the application is activated (brought to foreground)
// This code will not execute when the application is first launched
private void Application_Activated(object sender, ActivatedEventArgs e)
{
}
// Code to execute when the application is deactivated (sent to background)
// This code will not execute when the application is closing
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
}
// Code to execute when the application is closing (eg, user hit Back)
// This code will not execute when the application is deactivated
private void Application_Closing(object sender, ClosingEventArgs e)
{
}
// Code to execute if a navigation fails
private void RootFrame_NavigationFailed(object sender, NavigationFailedEventArgs e)
{
if (System.Diagnostics.Debugger.IsAttached)
{
// A navigation has failed; break into the debugger
System.Diagnostics.Debugger.Break();
}
}
// Code to execute on Unhandled Exceptions
private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
{
if (System.Diagnostics.Debugger.IsAttached)
{
// An unhandled exception has occurred; break into the debugger
System.Diagnostics.Debugger.Break();
}
}
#region Phone application initialization
// Avoid double-initialization
private bool phoneApplicationInitialized = false;
// Do not add any additional code to this method
private void InitializePhoneApplication()
{
if (phoneApplicationInitialized)
return;
// Create the frame but don't set it as RootVisual yet; this allows the splash
// screen to remain active until the application is ready to render.
RootFrame = new PhoneApplicationFrame();
RootFrame.Navigated += CompleteInitializePhoneApplication;
// Handle navigation failures
RootFrame.NavigationFailed += RootFrame_NavigationFailed;
// Ensure we don't initialize again
phoneApplicationInitialized = true;
}
// Do not add any additional code to this method
private void CompleteInitializePhoneApplication(object sender, NavigationEventArgs e)
{
// Set the root visual to allow the application to render
if (RootVisual != RootFrame)
RootVisual = RootFrame;
// Remove this handler since it is no longer needed
RootFrame.Navigated -= CompleteInitializePhoneApplication;
}
#endregion
}
}
这是我的app.xaml.cs，现在没有任何更改。使用此代码，墓碑在主页和详细信息页面中工作正常，但在（当然）页面中没有。
答案 0 :(得分：0)
我在如何从我的应用上的第2页恢复数据时遇到问题，我将此方法视为克服此问题的替代方法。
为什么不解决这个，真正的问题？您所要求的不太可能通过市场认证，通常被认为是糟糕的用户体验。
恢复数据非常简单。所以没有理由不这样做。
<强>更新
嗯，这看起来很可疑
FrameworkElement root = Application.Current.RootVisual as FrameworkElement;
currentFeed = root.DataContext as FeedViewModel;
RootVisual肯定是您尝试显示的页面本身？否则，它是另一个页面，根本没有加载。
解决方案是使用Application.Current.RootVisual中的DataContext进行避免。如果你问我，这通常是不好的做法。
因此，您需要在State属性中手动持久保存ViewModel，或者需要以其他方式解析它（我建议使用后者）。
但基本上你需要阅读更多有关如何为平台开发的内容。看看已知可行的一些示例/教程。
答案 1 :(得分：0)
在App.xaml.cs中查看以下方法：
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
private void Application_Activated(object sender, ActivatedEventArgs e)
以下是您应该保存并从分离存储加载状态数据的位置。
这也是您可以强制应用程序导航到另一个页面的地方，但我强烈建议不要这样做。用户不期望这种行为，也许你甚至不会在市场上发布。而且根本不难做到，你所要做的就是在这些方法中加载并保存你的状态。
到目前为止，您尝试做了什么？问题到底在哪里？