From ee46fb9228fd6e70893270703d814a400bb8ca22 Mon Sep 17 00:00:00 2001
From: Vitaly Takmazov
Date: Fri, 26 Apr 2013 22:04:18 +0400
Subject: Fixed crash when network is unavailable, added warning message

---
 Juick/ViewModels/AppViewModel.cs  | 52 ++++++++++++++++++++++++++++-----------
 Juick/ViewModels/PageViewModel.cs |  2 ++
 2 files changed, 39 insertions(+), 15 deletions(-)

(limited to 'Juick/ViewModels')

diff --git a/Juick/ViewModels/AppViewModel.cs b/Juick/ViewModels/AppViewModel.cs
index 7d5006c..07ba7cf 100644
--- a/Juick/ViewModels/AppViewModel.cs
+++ b/Juick/ViewModels/AppViewModel.cs
@@ -2,8 +2,10 @@
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
+using System.Net.NetworkInformation;
 using Juick.Classes;
 using JuickApi;
+using Microsoft.Phone.Net.NetworkInformation;
 using RestSharp;
 using Microsoft.Phone.Notification;
 using System.Diagnostics;
@@ -13,29 +15,37 @@ namespace Juick.ViewModels
 {
     public class AppViewModel : ViewModelBase
     {
-        readonly HttpNotificationChannel pushChannel; 
+        static readonly string IsNetworkAvailablePropertyName = ExpressionHelper.GetPropertyName<AppViewModel>(x => x.NetworkUnavailable);
+        readonly HttpNotificationChannel _pushChannel; 
 
         // The name of our push channel.
-        string channelName = "JuickChannel";
+        private const string channelName = "JuickChannel";
+
+        public void UpdateNetworkStatus()
+        {
+            NetworkUnavailable = !DeviceNetworkInformation.IsNetworkAvailable;
+        }
 
         public AppViewModel()
         {
-            pushChannel = HttpNotificationChannel.Find(channelName);
+            UpdateNetworkStatus();
+            NetworkChange.NetworkAddressChanged += (sender, args) => UpdateNetworkStatus();
+            _pushChannel = HttpNotificationChannel.Find(channelName);
 
                   // If the channel was not found, then create a new connection to the push service.
-            if (pushChannel == null)
+            if (_pushChannel == null)
             {
-                pushChannel = new HttpNotificationChannel(channelName);
+                _pushChannel = new HttpNotificationChannel(channelName);
 
                 // Register for all the events before attempting to open the channel.
-                pushChannel.ChannelUriUpdated += (sender, e) => EnableNotifications(e.ChannelUri.ToString());
-                pushChannel.ErrorOccurred += (sender, e) => DisableNotifications();
+                _pushChannel.ChannelUriUpdated += (sender, e) => EnableNotifications(e.ChannelUri.ToString());
+                _pushChannel.ErrorOccurred += (sender, e) => DisableNotifications();
 
                 // Register for this notification only if you need to receive the notifications while your application is running.
                 // Register for this notification only if you need to receive the notifications while your application is running.
-                pushChannel.ShellToastNotificationReceived += (sender, e) =>
+                _pushChannel.ShellToastNotificationReceived += (sender, e) =>
                 {
-                    StringBuilder message = new StringBuilder();
+                    var message = new StringBuilder();
                     string relativeUri = string.Empty;
 
                     message.AppendFormat("Received Toast {0}:\n", DateTime.Now.ToShortTimeString());
@@ -57,20 +67,20 @@ namespace Juick.ViewModels
                     Debug.WriteLine("Received: " + message.ToString());
                 };
 
-                pushChannel.Open();
+                _pushChannel.Open();
 
                 // Bind this new channel for toast events.
-                pushChannel.BindToShellToast();
+                _pushChannel.BindToShellToast();
 
             }
             else
             {
                 // The channel was already open, so just register for all the events.
-                pushChannel.ChannelUriUpdated += (sender, e) => EnableNotifications(e.ChannelUri.ToString());
-                pushChannel.ErrorOccurred += (sender, e) => DisableNotifications();
+                _pushChannel.ChannelUriUpdated += (sender, e) => EnableNotifications(e.ChannelUri.ToString());
+                _pushChannel.ErrorOccurred += (sender, e) => DisableNotifications();
 
                 // Register for this notification only if you need to receive the notifications while your application is running.
-                pushChannel.ShellToastNotificationReceived += (sender, e) =>
+                _pushChannel.ShellToastNotificationReceived += (sender, e) =>
                 {
                     StringBuilder message = new StringBuilder();
                     string relativeUri = string.Empty;
@@ -94,7 +104,7 @@ namespace Juick.ViewModels
                     Debug.WriteLine("Received: " + message.ToString());
                 };
 
-                EnableNotifications(pushChannel.ChannelUri.ToString());
+                EnableNotifications(_pushChannel.ChannelUri.ToString());
             }
         }
         private ObservableCollection<PageViewModel> _pages;
@@ -120,6 +130,18 @@ namespace Juick.ViewModels
             }
         }
 
+        private bool _isNetworkUnavailable;
+        public bool NetworkUnavailable
+        {
+            get { return _isNetworkUnavailable; }
+            set
+            {
+                _isNetworkUnavailable = value; 
+                NotifyPropertyChanged(IsNetworkAvailablePropertyName);
+            }
+        }
+
+
         private AccountManager _acc;
 
         public AccountManager Account
diff --git a/Juick/ViewModels/PageViewModel.cs b/Juick/ViewModels/PageViewModel.cs
index e398caf..ce48449 100644
--- a/Juick/ViewModels/PageViewModel.cs
+++ b/Juick/ViewModels/PageViewModel.cs
@@ -72,6 +72,8 @@ namespace Juick.ViewModels
             _context.Client.ExecuteAsync<List<Message>>(request, response =>
             {
                 _context.IsDataLoading = false;
+                if (response.Data == null)
+                    return;
                 response.Data.Select(x => new PostItem(x)).ToList().ForEach(i => Items.Add(i));
             });
             _context.IsDataLoading = true;
-- 
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