我正在构建一个Windows手机应用程序，我遇到了这个问题：我在FirstRun()文件中有一个App.xaml.cs函数，用于检查应用程序是否第一次运行。我有两个消息框，每次都给我看（第一次运行而不是第一次运行）。问题是，当我第一次运行应用程序时，我收到消息“第一次运行”但在此之后，没有继续，我得到另一条消息“不首先运行”，程序没有进入需要的功能在第一次运行时执行。什么可以导致IsFirstRun()函数的这个“双重”调用，并返回不同的结果？以下是功能：
public static bool IsFirstRun()
{
if (!settings.Contains(FIRST_RUN_FLAG)) //First time running
{
settings.Add(FIRST_RUN_FLAG, false);
return true;
}
return false;
}
UriMapper帮我找到了正确的页面：
公共类FirstRunUriMapper：UriMapperBase { 公开覆盖Uri MapUri（Uri uri） {
if (uri.OriginalString == "/LaunchPage.xaml")
{
MessageBox.Show("Searching for LaunchPage...");
if (App.IsFirstRun())
{
MessageBox.Show("First run...Should show introductionPage...");
uri = new Uri("/MainPage.xaml", UriKind.Relative);
}
else
{
MessageBox.Show("...Should show MainPage...");
uri = new Uri("/IntroductionPage.xaml", UriKind.Relative);
}
}
return uri;
}
}
修改
如我所知，我为整个班级提供了现在正常工作的修改后的UriMapper，但仍无法找到导致双MapUri()方法调用的原因：
public class FirstRunUriMapper : UriMapperBase
{
public override Uri MapUri(Uri uri)
{
if (uri.OriginalString == "/LaunchPage.xaml")
{
if (App.FirstRun)
{
if (App.IsFirstRun())
{
uri = new Uri("/IntroductionPage.xaml", UriKind.Relative);
}
else
{
uri = new Uri("/IntroductionPage.xaml", UriKind.Relative);
App.FirstRun = false;
}
}
else
{
uri = new Uri("/MainPage.xaml", UriKind.Relative);
}
}
return uri;
}
}
App.xaml.cs类：
公共部分类App：应用程序 {
private static string FIRST_RUN_FLAG = "FIRST_RUN_FLAG";
private static IsolatedStorageSettings settings = IsolatedStorageSettings.ApplicationSettings;
public static bool FirstRun = true;
/// <summary>
/// Provides easy access to the root frame of the Phone Application.
/// </summary>
/// <returns>The root frame of the Phone Application.</returns>
public static PhoneApplicationFrame RootFrame { get; private set; }
/// <summary>
/// Checks if the app runs for the first time
/// </summary>
/// <returns>True if the app runs for the first time, otherwise false.</returns>
public static bool IsFirstRun()
{
if (!settings.Contains(FIRST_RUN_FLAG)) //First time running
{
settings.Add(FIRST_RUN_FLAG, false);
return true;
}
return false;
}
public void loadModel()
{
string dataFromAppSettings;
ContactLensesModel model;
//Search for the string into the Application Settings
if (IsolatedStorageSettings.ApplicationSettings.TryGetValue(MainPage.Model.modelKey, out dataFromAppSettings))
{
model = JsonConvert.DeserializeObject<ContactLensesModel>(dataFromAppSettings);
MainPage.Model = model;
}
else //The model does not exist
{
MainPage.Model = null;
}
}
public void saveModel()
{
//Convert to a JSON format
var modelData = JsonConvert.SerializeObject(MainPage.Model);
//Save the model to the settings
IsolatedStorageSettings.ApplicationSettings[MainPage.Model.modelKey] = modelData;
IsolatedStorageSettings.ApplicationSettings.Save();
}
/// <summary>
/// Constructor for the Application object.
/// </summary>
public App()
{
// Global handler for uncaught exceptions.
UnhandledException += Application_UnhandledException;
// Standard XAML initialization
InitializeComponent();
// Phone-specific initialization
InitializePhoneApplication();
// Language display initialization
InitializeLanguage();
// Show graphics profiling information while debugging.
if (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 handed off to GPU with a colored overlay.
//Application.Current.Host.Settings.EnableCacheVisualization = true;
// Prevent the screen from turning off while under the debugger by disabling
// the application's idle detection.
// Caution:- Use this under debug mode only. Application that disables user idle detection will continue to run
// and consume battery power when the user is not using the phone.
PhoneApplicationService.Current.UserIdleDetectionMode = IdleDetectionMode.Disabled;
}
}
// 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)
{
RootFrame.UriMapper = new FirstRunUriMapper();
loadModel();
}
// 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)
{
loadModel();
if (e.IsApplicationInstancePreserved == false)
{
RootFrame.UriMapper = new FirstRunUriMapper();
}
}
// 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)
{
saveModel();
}
// 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)
{
saveModel();
}
// Code to execute if a navigation fails
private void RootFrame_NavigationFailed(object sender, NavigationFailedEventArgs e)
{
if (Debugger.IsAttached)
{
// A navigation has failed; break into the debugger
Debugger.Break();
}
}
// Code to execute on Unhandled Exceptions
private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
{
if (Debugger.IsAttached)
{
// An unhandled exception has occurred; break into the debugger
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;
// Handle reset requests for clearing the backstack
RootFrame.Navigated += CheckForResetNavigation;
// 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;
}
private void CheckForResetNavigation(object sender, NavigationEventArgs e)
{
// If the app has received a 'reset' navigation, then we need to check
// on the next navigation to see if the page stack should be reset
if (e.NavigationMode == NavigationMode.Reset)
RootFrame.Navigated += ClearBackStackAfterReset;
}
private void ClearBackStackAfterReset(object sender, NavigationEventArgs e)
{
// Unregister the event so it doesn't get called again
RootFrame.Navigated -= ClearBackStackAfterReset;
// Only clear the stack for 'new' (forward) and 'refresh' navigations
if (e.NavigationMode != NavigationMode.New && e.NavigationMode != NavigationMode.Refresh)
return;
// For UI consistency, clear the entire page stack
while (RootFrame.RemoveBackEntry() != null)
{
; // do nothing
}
}
#endregion
// Initialize the app's font and flow direction as defined in its localized resource strings.
//
// To ensure that the font of your application is aligned with its supported languages and that the
// FlowDirection for each of those languages follows its traditional direction, ResourceLanguage
// and ResourceFlowDirection should be initialized in each resx file to match these values with that
// file's culture. For example:
//
// AppResources.es-ES.resx
// ResourceLanguage's value should be "es-ES"
// ResourceFlowDirection's value should be "LeftToRight"
//
// AppResources.ar-SA.resx
// ResourceLanguage's value should be "ar-SA"
// ResourceFlowDirection's value should be "RightToLeft"
//
// For more info on localizing Windows Phone apps see http://go.microsoft.com/fwlink/?LinkId=262072.
//
private void InitializeLanguage()
{
try
{
// Set the font to match the display language defined by the
// ResourceLanguage resource string for each supported language.
//
// Fall back to the font of the neutral language if the Display
// language of the phone is not supported.
//
// If a compiler error is hit then ResourceLanguage is missing from
// the resource file.
RootFrame.Language = XmlLanguage.GetLanguage(AppResources.ResourceLanguage);
// Set the FlowDirection of all elements under the root frame based
// on the ResourceFlowDirection resource string for each
// supported language.
//
// If a compiler error is hit then ResourceFlowDirection is missing from
// the resource file.
FlowDirection flow = (FlowDirection)Enum.Parse(typeof(FlowDirection), AppResources.ResourceFlowDirection);
RootFrame.FlowDirection = flow;
}
catch
{
// If an exception is caught here it is most likely due to either
// ResourceLangauge not being correctly set to a supported language
// code or ResourceFlowDirection is set to a value other than LeftToRight
// or RightToLeft.
if (Debugger.IsAttached)
{
Debugger.Break();
}
throw;
}
}
}
}
答案 0 :(得分：0)
static bool first = true;
public override Uri MapUri(Uri uri)
{
if (uri.OriginalString == "/LaunchPage.xaml")
{
if (first) MessageBox.Show("Searching for LaunchPage...");
if (App.IsFirstRun())
{
if (first) MessageBox.Show("First run...Should show introductionPage...");
uri = new Uri("/MainPage.xaml", UriKind.Relative);
}
else
{
if (first) MessageBox.Show("...Should show MainPage...");
uri = new Uri("/IntroductionPage.xaml", UriKind.Relative);
}
}
first = false;
}
return uri;
}
答案 1 :(得分：0)
您是否尝试过连接RootFrame.UriMapper而不是覆盖？
private void Application_Launching(object sender, LaunchingEventArgs e)
{
RootFrame.UriMapper = new YourUriMapper();
}