Windows 商店应用程序在没有互联网时崩溃

Question

我正在创建我的第一个 Windows 商店应用程序，并且在启动期间我有几个 Web 服务调用，并且还定期通过该应用程序调用。但是我注意到当我因为网络服务调用而无法访问互联网时，我的应用程序将无法启动/崩溃或只是关闭。我希望我的应用程序以一些初始数据以正常方式启动，即使没有互联网访问也看起来正常。我从 webservice 获得的数据主要是我在各种文本框和图表中显示的天气数据。

下面的代码在我的扩展初始屏幕中显示了 Web 服务调用。

public sealed partial class ExtendedSplashScreen : Page
{

//parameterItem max1DayAgo = new parameterItem();
//parameterItem min1DayAgo = new parameterItem();


public ExtendedSplashScreen()
{
    this.InitializeComponent();
}

/// <summary>
/// Invoked when this page is about to be displayed in a Frame.
/// </summary>
/// <param name="e">Event data that describes how this page was reached.  The Parameter
/// property is typically used to configure the page.</param>
protected override async void OnNavigatedTo(NavigationEventArgs e)
{

    string[] periodSelector = { "1DayAgo", "1WeekAgo", "1MonthAgo" };
    string[] modeSelector = { "max", "min" };
    string[] parameterSelector = { "umtTemp1", "umtWindSpeed", "umtAdjBaromPress", "umtRainRate" };


    //Create a webservice object
    ServiceReference.WebServiceSoapClient webServiceObj = new ServiceReference.WebServiceSoapClient();
    //First we create an object that holds max data for yesterday
    var getMax1DayAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[0], modeSelector[0]);

    //create an object that holds min data for yesterday

    var getMin1DayAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[0], modeSelector[1]);
    //Save arrayOfValue and arrayOfUnit to a parameterItem object. these objects are created during startup
    // and the can be accessed and updated by all methods in this page later we will see that maxMinButton_Click method
    //for the maxMinButton will use these data

    //create an object that holds max data for last week
    var getMax1WekAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[1], modeSelector[0]);
    //create an object that holds min data for last week
    var getMin1WekAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[1], modeSelector[1]);
    //create an object that holds max data for last month
    var getMax1MonthAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[2], modeSelector[0]);
    //create an object that holds min data for last month
    var getMin1MonthAgoObj = await webServiceObj.GetSelectedMaxMinDataAsync(parameterSelector, periodSelector[2], modeSelector[1]);


    (App.Current as App).max1DayAgo.arrayOfValue = getMax1DayAgoObj.arrayOfValue;
    (App.Current as App).max1DayAgo.arrayOfUnit = getMax1DayAgoObj.arrayOfUnit;

    (App.Current as App).min1DayAgo.arrayOfValue = getMin1DayAgoObj.arrayOfValue;
    (App.Current as App).min1DayAgo.arrayOfUnit = getMin1DayAgoObj.arrayOfUnit;


    (App.Current as App).max1WeekAgo.arrayOfValue = getMax1WekAgoObj.arrayOfValue;
    (App.Current as App).max1WeekAgo.arrayOfUnit = getMax1WekAgoObj.arrayOfUnit;

    (App.Current as App).min1WeekAgo.arrayOfValue = getMin1WekAgoObj.arrayOfValue;
    (App.Current as App).min1WeekAgo.arrayOfUnit = getMin1WekAgoObj.arrayOfUnit;

    (App.Current as App).max1MonthAgo.arrayOfValue = getMax1MonthAgoObj.arrayOfValue;
    (App.Current as App).max1MonthAgo.arrayOfUnit = getMax1MonthAgoObj.arrayOfUnit;

    (App.Current as App).min1MonthAgo.arrayOfValue = getMin1MonthAgoObj.arrayOfValue;
    (App.Current as App).min1MonthAgo.arrayOfUnit = getMin1MonthAgoObj.arrayOfUnit;


    string[] startupData = new string[13];


    startupData[0] = " " + (App.Current as App).max1DayAgo.arrayOfValue[0] + " " + (App.Current as App).max1DayAgo.arrayOfUnit[0]; //    maxTemp 
    startupData[1] = " " + (App.Current as App).max1DayAgo.arrayOfValue[1] + " " + (App.Current as App).max1DayAgo.arrayOfUnit[1]; //    maxWindSped 
    startupData[2] = " " + (App.Current as App).max1DayAgo.arrayOfValue[2] + " " + (App.Current as App).max1DayAgo.arrayOfUnit[2]; //    maxAirPressure 
    startupData[3] = " " + (App.Current as App).max1DayAgo.arrayOfValue[3] + " " + (App.Current as App).max1DayAgo.arrayOfUnit[3];//     maxRainfall

    startupData[4] = " " + (App.Current as App).min1DayAgo.arrayOfValue[0] + " " + (App.Current as App).min1DayAgo.arrayOfUnit[0]; //    minTemp 
    startupData[5] = " " + (App.Current as App).min1DayAgo.arrayOfValue[1] + " " + (App.Current as App).min1DayAgo.arrayOfUnit[1];//     minWindSped 
    startupData[6] = " " + (App.Current as App).min1DayAgo.arrayOfValue[2] + " " + (App.Current as App).min1DayAgo.arrayOfUnit[2];//     minAirPressure  
    startupData[7] = " " + (App.Current as App).min1DayAgo.arrayOfValue[3] + " " + (App.Current as App).min1DayAgo.arrayOfUnit[3];//     minRainfall



    // Main fields
    // ServiceReference.WebServiceSoapClient webServiceObj = new ServiceReference.WebServiceSoapClient();
    var getLatestTempObj = await webServiceObj.GetLatestDataAsync("umtTemp1");
    var getLatestWindObj = await webServiceObj.GetLatestDataAsync("umtWindSpeed");
    var getLatestwindDirObj = await webServiceObj.GetLatestDataAsync("umtAdjWinDir");
    var getLatestairPressureObj = await webServiceObj.GetLatestDataAsync("umtAdjBaromPress");

    startupData[8] = " " + getLatestTempObj.Value + " " + getLatestTempObj.Unit;//temperatureMainTxtBlock.Text
    startupData[9] = " " + getLatestWindObj.Value + " " + getLatestWindObj.Unit;//temperatureMainTxtBlock.Text

    startupData[10] = "" + getLatestwindDirObj.Value; //temperatureMainTxtBlock.Text

    startupData[11] = " " + getLatestairPressureObj.Value + " " + getLatestairPressureObj.Unit;//temperatureMainTxtBlock.Text

    startupData[12] = "Last update: " + getLatestwindDirObj.Timestamp;//temperatureMainTxtBlock.Text
    //save the startup data to the global variables
    (App.Current as App).NavigateData = startupData;



    this.Frame.SetNavigationState(e.Parameter as string);
    this.Frame.Navigate(typeof(MainPage));
}
}

Answer 1

我们在一些基于团队的应用程序中采用的一种方法是在任何调用返回网络数据之前检查网络状态。示例：

async Task RefreshFromWeb(...) { if (!App.HasInternetAccess) { await new Windows.UI.Popups.MessageDialog(Strings.NoInternetWarning).ShowAsync(); return; } //attempt access here } public static bool HasInternetAccess { get { var profile = Windows.Networking.Connectivity.NetworkInformation.GetInternetConnectionProfile(); if (profile == null) return false; return profile.GetNetworkConnectivityLevel() == Windows.Networking.Connectivity.NetworkConnectivityLevel.InternetAccess; } }

我们有时也采取了另一种非常相似的方法，但使用 await 并返回 true 或 false（同样可以在上面轻松完成，上面的方法只是给出对话框）

public static async System.Threading.Tasks.Task HasInternet() { var profile = Windows.Networking.Connectivity.NetworkInformation.GetInternetConnectionProfile(); var hasNetAccess = profile != null; if (!hasNetAccess) await new Windows.UI.Popups.MessageDialog( content: InfoHub.AppHubViewModel.Strings.NoInternetWarning, title: InfoHub.AppHubViewModel.Strings.NoInternetWarning).ShowAsync(); return hasNetAccess; } async void YourControlEvent_Click(object sender, ItemClickEventArgs e) { //if net access, do your stuff, otherwise ignore for now if (await IsInternet()) { //do net calls here } }

Answer 2

您需要围绕这一行实现一些异常处理： ServiceReference.WebServiceSoapClient webServiceObj = new ServiceReference.WebServiceSoapClient();

并实现将在离线模式下工作的回退，即从缓存中检索数据。

Answer 3

您可以在App.xaml.cs 中使用NetworkStatusChanged 事件，然后您可以声明一个静态变量并使用它来检查Internet 是否可用。如果 Internet 可用，请执行您想要的操作，否则显示错误消息。

public static bool IsInternetAvailable;

void NetworkInformation_NetworkStatusChanged(object sender)
{
    if (NetworkInformation.GetInternetConnectionProfile() != null)
        App.IsInternetAvailable = true;
    else
        App.IsInternetAvailable = false;
}

当您有可能出现异常时，请始终使用 try catch 块。