Windows Phone 8 Fundamental

Windows Phone 8
App Development
7th April, 2013
Nguyen Pham
Pham.nguyen@Hotmail.com
http://phamnguyen.info

Windows Phone 8 Fundamentals
24/07/2013Microsoft confidential2
Windows Phone 8
Features of the platform
• Lifecycle
• Data
• Background
• App2app

Application
Lifecycle
7th April, 2013

Tombstoned
• Windows Phone apps transition between different
application states
• Apps are launched from Start Screen icon, apps menu
or from deep link
• User may close apps
• The OS will suspend your app if it loses focus
Suspended apps may be tombstoned
• Apps may be reactivated from a suspended state
• When the user starts a new instance of your app, any
suspended instance is discarded
• In Windows Phone 8.0, you can enable Fast Application
Resume to relaunch the suspended instance
Windows Phone Application Lifecycle
24/07/2013
Not running
Running
LaunchingClosing
DeactivatingActivating
Dormant

States and Tombstones
• When an application is resumed from Dormant, it resumes exactly where it left off
• All objects and their state is still in memory
• You may need to run some logic to reset time-dependent code or networking calls
• When an application is resumed from Tombstoned, it resumes on the same page where it left
off but all in-memory objects and the state of controls has been lost
• When a new instance of an applicatPersistent data will have been restored, but what about
transient data or “work in progress” at the time the app was suspended?
• This is what the state dictionaries are for, to store transient data
• State dictionaries are held by the system for suspended applications
• ion is launched the state dictionaries are empty
• If there is a previous instance of the application that is suspended, standard behaviour is
that the suspended instance – along with its state dictionaries - is discarded
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The Application State dictionary
• Transient data for a tombstoned application may be stored in the application state
dictionary
• This can be set in the Application_Deactivated method and then restored to memory
when the application is activated from tombstoned
• This means that the Application_Deactivated method has two things to do:
• Store persistent data in case the application is never activated again
• Optionally store transient data in the application state dictionary in case the user comes
back to the application from a tombstoned state
PhoneApplicationService.Current.State["Url"] = "www.robmiles.com";

Saving Transient Data on Deactivation
• Use the Page State dictionary to store transient data at page scope such as data the user has
entered but not saved yet
• Page and Application State are string-value dictionaries held in memory by the system but
which is not retained over reboots
protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedFrom(e);
if (e.NavigationMode != System.Windows.Navigation.NavigationMode.Back
&& e.NavigationMode != System.Windows.Navigation.NavigationMode.Forward)
{
// If we are exiting the page because we've navigated back or forward,
// no need to save transient data, because this page is complete.
// Otherwise, we're being deactivated, so save transient data
// in case we get tombstoned
this.State["incompleteEntry"] = this.logTextBox.Text;
}
}

Restoring Transient Data on Reactivation
• In OnNavigatedTo, if the State dictionary contains the value stored by OnNavigatedFrom,
then you know that the page is displaying because the application is being reactivated
protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
base.OnNavigatedTo(e);
// If the State dictionary contains our transient data,
// we're being reactivated so restore the transient data
if (this.State.ContainsKey("incompleteEntry"))
{
this.logTextBox.Text = (string)this.State["incompleteEntry"];
}
}

Manipulating the Back Stack
• This statement disables idle detection mode for your application
• It will now continue running under the lock screen
• An application can interrogate the back stack and also remove entries from it
• The method above would purge all the items in the stack
• A program can also enumerate the BackStack entries and find out where they point
• It is not possible to push entries onto the BackStack, nice though this would be
private void PurgeBackStackButton_Click(object sender, RoutedEventArgs e)
{
while (NavigationService.CanGoBack)
NavigationService.RemoveBackEntry();
}

Fast Application Resume
• By default a fresh instance of your application is always launched when the user starts a
new copy from the programs page or a deep link in a secondary tile or reminder, or via
new features such as File and Protocol associations or launching by speech commands
• This forces all the classes and data to be reloaded and slows down activation
• Windows 8 provides Fast Application Resume, which reactivates a dormant application if
the user launches a new copy
• This feature was added to enable background location tracking
• You can take advantage of it to reactivate a dormant application instead of launching a
new instance
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Enabling FAR in PropertiesWMAppManifest.xml
• This is how FAR is selected
• You have to edit the file by hand, there is no GUI for this
<Tasks>
<DefaultTask Name ="_default" NavigationPage="MainPage.xaml"/>
</Tasks>
<Tasks>
<DefaultTask Name ="_default" NavigationPage="MainPage.xaml">
<BackgroundExecution>
<ExecutionType Name="LocationTracking" />
</BackgroundExecution>
</DefaultTask>
</Tasks>

The Two Flavors of FAR
• Oddly, you enable FAR by registering your app as a “LocationTracking” app – whether or
not you actually track location!
• If you have marked your app LocationTracking *and* you actively track location by using
the GeoCoordinateWatcher or GeoLocator classes:
• App continues to run in the background if it is deactivated while actively tracking
• If re-launched from the Apps menu or via a Deep Link, the existing instance will be reactivated if it is
running in the background or fast resumed if it is dormant
• More on this in the Maps and Location Session!
• If you have marked your app LocationTracking but you don’t have any GPS code in your
app, then your app is one that can be fast resumed
• When deactivated, your app is suspended just like normal
• But when your app is relaunched and the previous instance is currently dormant, that previous
instance is fast resumed
24/07/201313

7th April, 2013
Files and Storage in
Windows Phone 8

File Type/ API
Installation
Folder
Local Folder Example
Local Database data
context
appdata:/ isostore:/
MyDataContext db = new MyDataContext
("isostore:/mydb.sdf")
Files access using
WP7.1 Isolated
Storage API
not supported
StorageFile and
StorageFolder
APIs
var isf =
IsolatedStorageFile.GetUserStoreForApplication()
File access using
Windows.Storage API
via URIs
ms-appx:///
ms-
appdata:///local/
var file = await
Windows.StorageFile.GetFileFromApplicationUriAsync(
new Uri("ms-appdata:///local/AppConfigSettings.xml"));
File access using
Windows.Storage API
via StorageFolder
references
Windows.
ApplicationModel.
Package.Current.
InstalledLocation
Windows.Storage.
ApplicationData.
Current.
LocalFolder
var localFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile storageFile =
await localFolder.GetFileAsync("CaptainsLog.store");
Different Methods For Addressing Storage Locations

• Three ways of getting a reference to the same file:
// WP7.1 IsolatedStorage APIs
var isf = IsolatedStorageFile.GetUserStoreForApplication();
IsolatedStorageFileStream fs = new IsolatedStorageFileStream("CaptainsLog.store", FileMode.Open, isf));
...
// WP8 Storage APIs using URI
StorageFile storageFile = await Windows.Storage.StorageFile.GetFileFromApplicationUriAsync(
new Uri("ms-appdata:///local/CaptainsLog.store "));
...
// WP8 Storage APIs
Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
Windows.Storage.StorageFile storageFile = await localFolder.GetFileAsync("CaptainsLog.store");
...
WP8 File Access Alternatives

Application Settings
• If you just want to store setting information
• Username = “Fred”
• TextColor = “Green”
• ..you can use the ApplicationSettings object in Isolated Storage
• You use this as you would a dictionary
• You then write the object to persistent storage

Saving Data in Settings
• The storage works as a dictionary
• But you have to remember to call Save when you have finished adding keys
void saveString(string message, string name)
{
IsolatedStorageSettings.ApplicationSettings[name] =
message;
IsolatedStorageSettings.ApplicationSettings.Save();
}

Loading from Settings
• Test for the key before you try to find it or you will get an exception thrown
2
2
string loadString(string name)
{
if (IsolatedStorageSettings.ApplicationSettings.
Contains(name))
{
return (string)
IsolatedStorageSettings.ApplicationSettings[name];
}
else
return null;
}

Windows.Storage Classes
• Windows Phone Runtime storage classes are in the Windows.Storage
namespace
• StorageFolder
• Represents a storage area containing files and directories
• StorageFile
• Represents a file and provides methods for manipulating them
• Not supported on Windows Phone 8:
• ApplicationData.LocalSettings
• Use custom file or IsolatedStorageSettings

Saving Data – Using StorageFolder
private async void saveToLocalFolderAsync(string message)
{
// Get a reference to the Local Folder
Windows.Storage.StorageFolder localFolder =
Windows.Storage.ApplicationData.Current.LocalFolder;
// Create the file in the local folder, or if it already exists, just open it
Windows.Storage.StorageFile storageFile =
await localFolder.CreateFileAsync("Myfile.store",
CreationCollisionOption.OpenIfExists);
Stream writeStream = await storageFile.OpenStreamForWriteAsync();
using (StreamWriter writer = new StreamWriter(writeStream))
{
await writer.WriteAsync(logData);
}
}

Loading Data
private async string loadStringAsync()
{
string theData = string.Empty;
// Get a reference to the file in the Local Folder
Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFile storageFile = await localFolder.GetFileAsync(“Myfile.store"));
// Open it and read the contents
Stream readStream = await storageFile.OpenStreamForReadAsync();
using (StreamReader reader = new StreamReader(readStream))
{
theData = await reader.ReadToEndAsync();
}
return theData;
}

Local Folder
• All read-write I/O operations
restricted to local folder
• Create a files and folder structure
hierarchy
• Use Isolated Settings storage to
store application settings

Reserved Folders
• In addition to general data storage, the local folder
is used for the following special-use scenarios:
• Shared/Media - Apps can use this folder to
display album art in the Universal Volume Control
(UVC) while playing background audio
• Shared/ShellContent - Background images for
Tiles can be stored in isolated storage, but must
be located in this folder or a subfolder of it
• Shared/Transfers – Storage area used by the
Background File Transfer service
24/07/201329

• Windows Phone 8 devices support SD cards
• App can read files stored on a storage card
• Must declare the ID_CAP_REMOVABLE_STORAGE capability in the application
manifest file
• Cannot write files - Access is Read Only
• Can only access file types for which your app has registered a file association in
WMAppManifest.xml
External Storage (SD Card)
24/07/2013

7th April, 2013
Background
Agents
New updates
from
Background
Agent

Foreground Tasks
• Normally a Windows Phone application runs in the “foreground”
• Has access to screen and interacts directly with the user of the phone
• At any given time one application is running in the foreground
• Although others may be in the memory of the phone and can be selected
as required
• This is to ensure the best possible performance and battery life for the phone user
32

Background Agents
• A Windows Phone application can start a “background agent” to work for it
• It is a PeriodicTask, ResourceIntensiveTask or both at the same time
• There is only one agent allowed per application
• The agent can run when the main application is not in the foreground
• An agent is not equivalent to a foreground application running in the background
• It is limited in what it can do and the access it has to the processor
and other phone facilities
33

Agents and Tasks
• A Task is the scheduling type you request when you schedule a background agent to run
• It is managed by the operating system which runs the agent at the appointed time
• There are two kinds of Tasks
• Periodic tasks that are run every now and then
• Resource intensive tasks that run when the phone is in a position to let them
• The background Agent is the actual code functionality you write which runs in the
background and which does the work
• The agent code is implemented in a class that derives from BackgroundAgent
• The class is created as part of a Scheduled Task Agent Project
34

PeriodicTask Agents
• A PeriodicTask Agent runs every now and then
• Typically every 30 minutes or so, depending on loading on the phone
• It is intended to perform a task that should be performed regularly
and complete quickly
• The agent is allowed to run for 25 seconds or so
• Memory usage allowed<= 6 MB
• Unscheduled after two consecutive crashes
• The phone sets a limit on the maximum number of active agents at any time
• Good for location tracking, polling background services, tile updates
35

ResourceIntensive Agents
• Resource Intensive Agents run when the phone is in a position where it can usefully
perform some data processing:
• When the phone is powered by the mains
• When the battery is >90% charged
• When the phone is connected to WiFi
• When the phone is not being used (Lock screen displayed)
• A “resource intensive” agent can run for up to 10 minutes
• Memory usage allowed<= 6 MB
• Unscheduled after two consecutive crashes
• Good for synchronisation with a host service, unpacking/preparing resources, compressing
databases
36

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Background Agent Functionality

• The code shown in this sample gets a new location whenever the Periodic agent runs
• Every 30 minutes or so
• Windows Phone 8 supports continuous background location tracking
• Suitable for Run Tracking apps and Turn-by-Turn navigation
• This is not covered here!
• See the Location and Maps module
Background Location Tracking
24/07/201338

Background Agent Tips
• Renew often
• You must reschedule agents from your foreground app at least every two weeks
• Do not implement critical functionality in a background agent
• User can disable them
• OS can suspend them in low battery situation
• If you need more reliable execution of code outside your application and need to update
Tiles or send Toast notifications, consider Push Notifications

File Transfer Tasks
• It is also possible to create a background task to transfer files to and from your
application’s isolated storage
• The transfers will take place when the application is not running
• An application can monitor the state of the downloads and display their status
• Files can be fetched from HTTP or HTTPS hosts
• At the moment FTP is not supported
• The system maintains a queue of active transfers and services each one in turn
• Applications can query the state of active transfers
40

Background Transfer Policies
• There are a set of policies that control transfer behaviour
• Maximum Upload file size: 5Mb
• Maximum Download file size over cellular (mobile phone) data: 20Mb
• Maximum Download file size over WiFi: 100Mb
• These can be modified by setting the value of TransferPreferences
on a particular transfer
• Maximum number of Background Transfer Requests per app: 25
• Increased from 5 in Windows Phone OS 7.1
41

Audio Playback Agents
• Also possible to create an Audio Playback Agent
that will manage an application controlled
playlist
• The mechanism is the same as for other
background tasks
• The audio can be streamed or held in the
application isolated storage
42

7th April, 2013
App to App
Communication
This App   This App

Agenda
File and Protocol
Associations
Launching Apps to Handle
Particular File Types
Launching one App from
Another
Auto-Launching with File and Protocol
Associations
Automatically launch your app when another app launches a
particular file type or protocol
File associations allow your app to launch to handle an email
attachment, a file opened in Internet Explorer or by another
app

• File associations allow your app to launch when the user wants to open a particular file
type, via:
• an email attachment
• a website via Internet Explorer
• a text message
• a Near Field Communications (NFC) tag
• another app from the Store
• Protocol association allows your app to automatically launch when another app launches a
special URI
• Protocol is the first part of a URI, e.g. myprotocol:/ShowProducts?CategoryID=aea6ae1f
• Your app launches another and passes it data in the remainder of the launch URI
Auto-launching with File and Protocol Associations

• Like Windows 8, Windows Phone 8 uses
LauncherLaunchFileAsync(IStorageFile) to launch a file and
LauncherLaunchUriAsync(Uri) to launch a URI
• However, the way Windows Phone XAML apps receive a file or
URI is different
• Windows 8 has a “default” Store app for a file type or URI, so that
will be launched
• In Windows Phone 8, if there are multiple Store apps installed that
can handle a particular file or protocol association, the user
chooses the receiving app from a menu
Comparison with Windows 8 User Experience

• To handle a particular file type, register for a file association in the app manifest file
• Optionally supply logos that Windows Phone OS will use when listing files
• Edit WMAppManifest.xml using the XML (Text) Editor
Registering for a File Association
Logo Size Use Dimensions
Small Email attachments 33x33 pixels
Medium Office hub list view 69x69 pixels
Large Browser download 176x176 pixels

• When your app is launched to handle a file, a deep link URI is sent to your app
/FileTypeAssociation?fileToken=89819279-4fe0-4531-9f57-d633f0949a19
• You need to implement a custom URI Mapper to parse the deep link URI and map to a
page in your app that will handle it
Listening for a file launch
FileTypeAssociation designates
that the source of the URI is a file type
association
The file token

Local Storage
SharedStorage
• Files passed to an app are stored by the OS
in a special folder called SharedStorage
• Receiving apps only have read access to
this folder
• Copy file to local storage to access it
Accessing the File
24/07/201349

• Your app can launch a file so another app can open it
Sending a File to Another App
24/07/201350
private async void LaunchFileButton_Click(object sender, RoutedEventArgs rea)
{
// Access local storage.
StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
// Access the bug query file.
StorageFile bqfile = await local.GetFileAsync("file1.bqy");
// Launch the bug query file.
Windows.System.Launcher.LaunchFileAsync(bqfile);
}

• Many file extensions are reserved for the built-in apps
• .cer, .doc, .docx, .jpg, .mp3, .pptx … etc..
• Many more reserved by the OS
• .ade, .adp ….[ > 100 in total! ] … .xnk
• If you try to reserve a file association using one of the reserved types, the reservation
request will be ignored
• See the documentation for a full list of the reserved file types
Reserved File Associations

URI scheme Description
http:[URL]
Launches the web browser and navigates to the specified
URL.
mailto:[email address]
Launches the email app and creates a new message with the
specified email address on the To line.
Note that the email is not sent until the user taps send.
ms-settings-accounts: Launches the Account Settings app.
ms-settings-airplanemode: Launches the Airplane Mode Settings app.
ms-settings-bluetooth: Launches the Bluetooth Settings app.
ms-settings-cellular: Launches the Cellular Settings app.
ms-settings-emailandaccounts: Launches the email and accounts settings app.
ms-settings-location: Launches the Location Settings app.
ms-settings-lock: Launches the Lock Screen settings app.
ms-settings-wifi: Launches the Wi-Fi Settings app.
Launching Built-in Apps
Use LaunchUriAsync to launch many of the built-in apps

Launching Built-in Apps (cont)
URI scheme Description
zune:navigate?appid=[app ID]
Launches the Windows Phone Store and shows the details
page for the specified app.
zune:reviewapp
Launches the Store and shows the review page for the
calling app.
zune:reviewapp?appid=[app ID]
Launches the Store and shows the review page for the
specified app.
zune:search?[search parameter]=[value] Launches the Store and searches for the specified content.
zune:search?keyword=[search keyword]
&contenttype=app
Launches the Store and searches for apps by keyword.
zune:search?publisher=[publisher name]
Launches the Store and searches for items by publisher
name.

The information herein is for informational
purposes only an represents the current view of
Microsoft Corporation as of the date of this
presentation. Because Microsoft must respond
to changing market conditions, it should not be
interpreted to be a commitment on the part of
Microsoft, and Microsoft cannot guarantee the
accuracy of any information provided after the
date of this presentation.
© 2012 Microsoft Corporation.
All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION
IN THIS PRESENTATION.

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