Windows Phone 7 platform overview. Mobile application development for Windows Phone platform basics. Multitasking and services with Phone 7.

1. WINDOWS PHONE 7
MULTITASKING & BACKGROUND
TASKS
Rom an Ivasyshyn
Softj
ourn Inc.

2. Topics

Platform overview

Multi-Tasking with background agents

Windows Phone Task Manager

Background Notifications

File Transfer Tasks, Music Playback Tasks

3. Platform overview

Intelligent OS and well designed API

Powerful instrumentation and language

Up to date mobile OS

WP7 Marketplace now available for Ukraine

Multitasking

Push notifications

Implementation of social network API

4. Foreground tasks

Normally a windows phone application runs in
the foreground

At any given time one application is running in
the foreground

This is to ensure the best performance and
battery life for the phone user

5. Background agents

Windows Phone application can start a
background agent.
− It is PeriodicTask, ResourceIntensiveTask or both at
same time
− There is only one agent allowed per application

The agent can run only when the main
application is not in the foreground

Agent is not equivalent to foreground
application running in the background
− It's limited in what it can do and the access it has the
processor and other phone facilities

6. Background Agent restriction

The number of Agents allowed to be active at one time is
restricted by the Windows Phone system

If the right conditions do not arise, Agent will not be
started
− The background agents only run in situations where the system feels
able to give them access to the processor

If the phone goes into “Power Saver” mode it may stop
running background agents completely

User can also manage the agents running on their phone
and may chose to disable them

Don't put any critical logic into yours app background
agent

7. Agent and Tasks

A Task is the container that is managed by the
operation system and runs at the appointed
time

It runs an Agent which does the work
− The agent code is called as a method in a class
− The class is created as part of a Scheduled Task Agent
Project

There are two kinds of Task
− Periodic tasks that are runs through a certain period of
time
− Resource intensive tasks that run where the phone in a
position to let them

8. Periodic task agent

A periodic task agent runs every
− Typically every 30 minutes or more, depends on phone
loading

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 less
− The phone sets a limit on the maximum number of active
at any time

Good for location tracking, polling background
services etc.

9. Resource intensive agents

Resource intensive agents run where the
phone is in a position where it can usefully
perform some data processing
− Where the phone is powered by the main
− Where the phone is connected to WiFi
− Where the phone is not being used (locked screen
displayed)

A “Resource Intensive”
agent can run for up to
10 minutes

10. Dual purpose agent

It is possible for application to perform both
periodic and resource intensive tasks in the
same time

This can be achieved using a single
background agent class, run from both kind of
task

The agent will run periodically and when phone
is in a position to allow resource intensive work

When the agent starts it can determine the
context in which it is running and then behave
appropriate

11. Background and Foreground
communication

For Periodic and Resource-intensive Agents:
− LINQ 2 SQL, file in isolated storage that is guarded with a
Mutex.
− Avoid IsolatedStorageSettings

For Audio Agents: Store custom data in the Tag
property of the AudioTrack class.

Use methods NotifyConplete or Abort to set
state flag

Toast and Tile notification

12. Windows Phone Task Manager

13. File transfer tasks

It is also possible to create a background task
to transfer files to and from your application's
isolate storage

The transfers may perform where the
application is not running

File can be downloaded from HTTP or HTTPS
hosts

The system maintains a queue of active
transfers and services

Application can query the state of active
transfer

14. Background transfer policies

There are a set of policies that control transfer
behavior
− Maximum Upload file size: 5Mb
− Maximum Download file size over cellular: 20Mb
− Maximum Downloads file over WiFi: 100Mb

These can be modified by setting the value of
TransferPreferences on the particular transfer

15. Audio Playback Agent

The audio can be streamed

There are no ability to play music from library
(only from application's isolate storage)

16. Conclusion

Use background tasks to perform particular job

DO NOT put any critical logic into yours app
background agent

There are a set of default backgrounds agent
designed for common tasks

17. Questions