Multitasking for Microsoft Windows Phone

Introduction

While Windows
Phone
platform brought a new and much improved mobile operating system from
Microsoft, the first version did not have the platform maturity its rivals
enjoyed at the moment. However with Windows Phone Mango, also called the 7.5
version of the Windows Phone operating system, Microsoft brought in about 500
changes from the 7.0 release, the primary being the multitasking, which
brought with it parity with its rivals.

For performance optimization, Windows Phone runs only one
process in the foreground (unlike our desktops which can run quite a few). To
ensure that user experience is optimal, Windows Phone Mango now has the ability
to run an application in the background (so display resources are only utilized
for the process running in the foreground).

With Windows Phone 7.5, the support for multitasking has
added new possibilities in what the Windows Phone user can now do. Let us take
a look at what new scenarios are enabled as a result of multitasking.

Background Audio

You no longer are constrained to keeping your Music player
application running while you desperately want to check your Facebook Wall or
the latest YouTube trending video. An application developer can create an
AudioPlayerAgent, which can run in the background rendering your favorite tunes
while you check your email /Facebook posts.

Scheduled Tasks

multitasking in the Windows Phone platform enables scheduled
tasks. This feature allows applications to run code in the background when the
main application is not running. Check out the Background Agents article for
more details on this.

Background File Transfers

You no longer have to wait for an active download in your
application to move on to the next important thing on your phone. Windows Phone
Mango allows applications to use the background transfer service to queue
downloads, which can be performed when the application is not running in the
foreground. At the time of writing this article, both uploading and downloading
files in the background are supported.

The APIs reside in the Microsoft.Phone.BackgroundTransfer
class.

Scheduled Notifications

This is akin to the alarm clock facility, however, this
feature is meant for an application to set up reminders to launch itself. The
reminders can be one-time or recurring. You can use the ScheduledNotification
class to do this.

Faster Application Switching

With Windows Phone 7.0, any action that navigated a user
away from the application would result in termination of the application. With
Windows Phone 7.5, this behavior has changed for the better. Upon navigating
away, an application is put into a dormant state. When the user navigates back
to the application, it restores its state and hence it can resume instantly
without any performance delays. This feature is on by default, so applications
do not have to write even a single line of code to support this.

Tombstoning

While discussing the new possibilities unleashed by
multitasking, we should not forget that primary drives, which enables this
behavior. Due to the limited resources available on these mobile devices, the
operating system will try to swap resources from an idle application and give
them to an in-use application. While developers in general dislike this
feature, they have to account for this Windows Phone operating system behavior
in their application invocation scenarios and architect their application
accordingly. An application can be tombstoned away and resurrected back.
Tombstoning also follows a Deactivated event, although a deactivated
application isn’t guaranteed to be tombstoned.

An application enters the Deactivated/Tombstoned stage
usually when the user presses the Start button, or the lock screen comes up, or
a user clicks a popped-up toast of another application and navigates to it.

In all such cases, the application needs to handle the state
transition accurately to allow the application user a pleasant experience.

Summary

In this article, we learned about the new features that are
enabled on the Windows Phone platform by the introduction of multitasking in
Mango.

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