How do I prevent the blog reader template from crashing when there is no internet connection? I want the app to display an error message rather than crashing. I assume there is some code missing in data.js below:
(function () {
"use strict";
// Set up array variables
var dataPromises = [];
var blogs;
// Create a data binding for our ListView
var blogPosts =
new WinJS.Binding.List();
// Process the blog feeds
function getFeeds() {
// Create an object for each feed in the blogs array
// Get the content for each feed in the blogs array
// Return when all asynchronous operations are complete
// Create an object for each feed in the blogs array
blogs = [
{
key:
"blog1",
url:
'http://blogs.windows.com/windows/b/windowsexperience/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog2",
url:
'http://blogs.windows.com/windows/b/extremewindows/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog3",
url:
'http://blogs.windows.com/windows/b/business/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog4",
url:
'http://blogs.windows.com/windows/b/bloggingwindows/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog5",
url:
'http://blogs.windows.com/windows/b/windowssecurity/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog6",
url:
'http://blogs.windows.com/windows/b/springboard/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog7",
url:
'http://blogs.windows.com/windows/b/windowshomeserver/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog8",
url:
'http://blogs.windows.com/windows_live/b/developer/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog9",
url:
'http://blogs.windows.com/ie/b/ie/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog10",
url:
'http://blogs.windows.com/windows_phone/b/wpdev/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
},
{
key:
"blog11",
url:
'http://blogs.windows.com/windows_phone/b/wmdev/atom.aspx',
title:
'tbd', updated: 'tbd',
acquireSyndication: acquireSyndication, dataPromise:
null
}];
// Get the content for each feed in the blogs array
blogs.forEach(function (feed) {
feed.dataPromise = feed.acquireSyndication(feed.url);
dataPromises.push(feed.dataPromise);
});
// Return when all asynchronous operations are complete
return WinJS.Promise.join(dataPromises).then(function () {
return blogs;
});
}
function acquireSyndication(url) {
// Call xhr for the URL to get results asynchronously
return WinJS.xhr(
{
url: url,
headers: {
"If-Modified-Since":
"Mon, 27 Mar 1972 00:00:00 GMT" }
});
}
function getBlogPosts() {
// Walk the results to retrieve the blog posts
getFeeds().then(function () {
// Process each blog
blogs.forEach(function (feed) {
feed.dataPromise.then(function (articlesResponse) {
var articleSyndication = articlesResponse.responseXML;
if (articleSyndication) {
// Get the blog title
feed.title = articleSyndication.querySelector("feed > title").textContent;
// Use the date of the latest post as the last updated date
var published = articleSyndication.querySelector("feed > entry > published").textContent;
// Convert the date for display
var date = new Date(published);
var dateFmt = new Windows.Globalization.DateTimeFormatting.DateTimeFormatter(
"month.abbreviated day year.full");
var blogDate = dateFmt.format(date);
feed.updated =
"Last updated " + blogDate;
// Get the blog posts
getItemsFromXml(articleSyndication, blogPosts, feed);
}
else {
// There was an error loading the blog.
feed.title =
"Error loading blog";
feed.updated =
"Error";
blogPosts.push({
group: feed,
key:
"Error loading blog",
title: feed.url,
author:
"Unknown",
month:
"?",
day:
"?",
year:
"?",
content:
"Unable to load the blog at " + feed.url
});
}
});
});
});
return blogPosts;
}
function getItemsFromXml(articleSyndication, bPosts, feed) {
// Get the info for each blog post
var posts = articleSyndication.querySelectorAll("entry");
// Process each blog post
for (var postIndex = 0; postIndex < posts.length; postIndex++) {
var post = posts[postIndex];
// Get the title, author, and date published
var postTitle = post.querySelector("title").textContent;
var postAuthor = post.querySelector("author > name").textContent;
var postPublished = post.querySelector("published").textContent;
// Convert the date for display
var postDate = new Date(postPublished);
var monthFmt = new Windows.Globalization.DateTimeFormatting.DateTimeFormatter(
"month.abbreviated");
var dayFmt = new Windows.Globalization.DateTimeFormatting.DateTimeFormatter(
"day");
var yearFmt = new Windows.Globalization.DateTimeFormatting.DateTimeFormatter(
"year.full");
var blogPostMonth = monthFmt.format(postDate);
var blogPostDay = dayFmt.format(postDate);
var blogPostYear = yearFmt.format(postDate);
// Process the content so it displays nicely
var staticContent = toStaticHTML(post.querySelector("content").textContent);
// Store the post info we care about in the array
bPosts.push({
group: feed,
key: feed.title,
title: postTitle,
author: postAuthor,
month: blogPostMonth.toUpperCase(),
day: blogPostDay,
year: blogPostYear,
content: staticContent
});
}
}
var list = getBlogPosts();
var groupedItems = list.createGrouped(
function groupKeySelector(item) {
return item.group.key; },
function groupDataSelector(item) {
return item.group; }
);
WinJS.Namespace.define("Data", {
items: groupedItems,
groups: groupedItems.groups,
getItemReference: getItemReference,
getItemsFromGroup: getItemsFromGroup,
resolveGroupReference: resolveGroupReference,
resolveItemReference: resolveItemReference
});
// Get a reference for an item, using the group key and item title as a
// unique reference to the item that can be easily serialized.
function getItemReference(item) {
return [item.group.key, item.title];
}
// This function returns a WinJS.Binding.List containing only the items
// that belong to the provided group.
function getItemsFromGroup(group) {
return list.createFiltered(function (item) {
return item.group.key === group.key; });
}
// Get the unique group corresponding to the provided group key.
function resolveGroupReference(key) {
for (var i = 0; i < groupedItems.groups.length; i++) {
if (groupedItems.groups.getAt(i).key === key) {
return groupedItems.groups.getAt(i);
}
}
}
// Get a unique item from the provided string array, which should contain a
// group key and an item title.
function resolveItemReference(reference) {
for (var i = 0; i < groupedItems.length; i++) {
var item = groupedItems.getAt(i);
if (item.group.key === reference[0] && item.title === reference[1]) {
return item;
}
}
}
})();
