Windows 8 DevUnleashed - Session 3

Session III – Lifecycle and More

Daryl Rudolph

Agenda

ApplicationLifecycle

Live Tiles, Background Process andLock Screen

Implementing the Search Contract

Application Lifecycle

Show the flow

Feel Connected and Alive

Memory Management

User selects app for foreground

System manages app lifetime

User launches many apps

User manages app lifetime

App process lifetime

RunningApp

SuspendedApp

Suspending Terminated

AppLow

MemoryResumin

g

Application States

Running

SuspendedNot Running

Resuming

Activated Suspending

Process lifetime walkthrough

App 1 App 2 App 3Running

Suspended

Terminated

… App N

Apps suspend after a short

delay

App terminated under memory

pressure without notification

Apps resume instantly from

suspend

When do apps get terminated

• System needs more memory• User switch occurs• System shutdown• Apps crash

Apps do not get notified when they are getting

terminated

Process state transitions

Running

App

SuspendedApp

suspendingTermina

tedApp

Low Memory

Code gets to runNo

code runs

App not running

resuming

App gets 5seconds to

handle suspend

App is not notified before

termination

Apps are notified when they have been resumed

User Launches App

Splash screen

Suspend under the hood

• Suspended apps are not scheduled by the NT Kernel

• No CPU, Disk or Network consumed• All threads are suspended• Apps remain in memory• Kernel ensures apps are not suspended in critical

sections that could cause system wide deadlocks• Apps instantly resumed from suspend when

brought to foreground

Interacting with your users

Entice Discover Share

App Activation Through Contracts

• Apps are activated through contracts• Launch, search, ShareTarget, etc.

• Apps need to initialize contract specific actions

• Context is provided

Running App

launch

shareTarget

activated

kind

search

App crash? Start over

• Apps that are stuck are no fun• Your app can be terminated abruptly in any of

these cases• Too long to load• Too long to suspend• Stopped handling input messages (Blocking I/O on UI

thread)• Task manager

• Bring the user back home, and ignore saved user session state

• previousExecutionState is provided in activation event args

Best practices for saving and restoring state

Scenario You should….User is using your App

• Save user data incrementally

App switched away from (Suspending)

• Save where the user is – what screen they are on, for example

Not running App launched by user (Activated)

• Bring the user back and restore their session as if they never left

Suspended App launched by user (Resuming)

• Do nothing

Demo

Suspend Demo

Search Contract

Finding your application

Use the Right Contracts

Search 1 2 3

1. Search box is scoped to the main app on screen

2. Query suggestions provided by the main app on screen• Autocompletes to terms for

which the app has search results

3. List of installed Windows 8 style apps that have implemented the search contract

2

3

1

Query submitted

User

Show Search results view

Yes

Show previous

search results view

NoQuery chang

ed?

User enters a query and hits

Search

User selects a query

suggestion

Search Pane

Submit query to App

Search App

Query Submitted

Event

Demo

Search Contract Demo

Live tiles

Keep the action going

Invest in a Great Tile

Tiles Sizes• Tap on tile to launch or switch to an

app

• Static default tile specified in app manifest

• Two sizes:

Both sizes can have live updates

Wide (2x1)

310X150

Square (1x1)

150X150

Badges

• Overlays status on top of tile• Supports square and wide tiles• Number up to 99 or pre-defined glyph:

• Always legible on top of images

BadgeBadge

Notification Queuing

• By default only last notification shown• Opt-in to automatically cycle tile through last five

notifications

Live Tiles things to remember

• Tiles updated using pre-defined templates

• Text-only, image-only or combination• JPEG or PNG only, max size 150 KB• Local, cloud or background updates

Invest in a Great Tile

Demo

Live Tiles

Secondary Tiles

• Tiles created by “pinning” content from app

• Pin initiated by app via simple runtime call

• User confirms pin operation via system UI

• Exposes a personalized surface for app

• Same capabilities as app tiles• Launch leads to relevant content

Demo

Secondary Tiles

RTC – Real Time Communication apps

Keep the action going

Invest in a Great Tile

Review app process lifetime

RunningApp

SuspendedApp

Suspending Terminated

AppLow

MemoryResumin

g

…with RTC apps

RunningApp

SuspendedApp

Suspending Terminated

AppLow

MemoryResumin

g

BackgroundTask

Executes

The app lifecycle

BackgroundTask

Executes

BackgroundTask

Executes

Network Trigger

RTC trigger APIs

System Trigger Time Trigger

Background Task Infrastructure

VoIP IM Your App

App

OS

Network Trigger

System Trigger

Time Trigger

Background Task Infrastructure

VoIP IM Mail

Changing Live Tile

Time Trigger

Setting up a Time Trigger

Live tiles with push notifications

• Tiles can be updated even if your app is not running!

• Push notifications can be used to remotely update a tile on the Start screen

• Great for showing the newest content available to your users

App Cloud Service

Windows Push Notification Service

(WNS)

HTTP POST

Notification Delivered

Push Notification Overview

1. Request Channel URI

2. Register with your Cloud Service

3. Authenticate & Push Notification

Windows 8

Notification

Client Platform

Windows 8 Style

App

App Service

Windows Push Notification

Service

1

2

3

3

POST <channel URI> HTTP/1.1Content-Type: text/xmlHost: db3.notify.windows.comX-WNS-Type: wns/badgeAuthorization: Bearer <authentication token>Content-Length: 58

<?xml version="1.0" encoding="utf-8"?><badge value="11"/>

Register for Time TriggerTime Trigger

using Windows.ApplicationModel.Background;

// Specify the triggerTimeTrigger trigger = new TimeTrigger(UpdateInterval, Periodic);

Create time

trigger

// Associate app code with the triggerBackgroundTaskBuilder taskBuilder = new BackgroundTaskBuilder();taskBuilder.TaskEntryPoint = “MyApp.Background.UpdateEmailTask";taskBuilder.SetTrigger(trigger);taskBuilder.Name = “TimerExpiry";

Associate trigger

with app code

// Register the task for background executionIBackgroundTaskRegistration taskRegistration = taskBuilder.Register();

Register trigger

public sealed class UpdateLiveTileTask : IBackgroundTask { public void Run(IBackgroundTaskInstance taskInstance) {

// Your app code to update email }}}

using Windows.ApplicationModel.Background;

Time Trigger App execution upon

timer expiry

Demo

Live Tiles /Lock Screen/Background

Best Practices for Tiles

• Display new, tailored and engaging content to the user

• Keep tile fresh by updating as your app content changes

• Reference content that lives on your app’s home page so the user can find it easily.

• Keep content safely ignorable and glanceable - for short messages only

• Use square size if tile is not live• No display ads!

Agenda

ApplicationLifecycle

Live Tiles, Background Process andLock Screen

Implementing the Search Contract

Hands-On Lab 3 OR Create your own app

Running in the background

Create your own app

• You can work on Hands-on Lab 3 OR Create your own app• You have until 4:20 PM• Don’t have to decide if you are entering until 4:20 PM• Presentation can be PowerPoint and/or demonstration

• Must let me know beforehand if you don’t have VGA connection

• Each contestant will have exactly 3 minutes to present!• Be creative. Keep in mind the traits of a great Windows 8

app!

• Note: Anyone who attended today can enter to win the app contest sponsored by Component Art for a $10,000 grand prize, even if you don’t enter today’s contest.

Contact/References

• Magenic – http://www.magenic.com• Daryl Rudolph – darylr@magenic.com

• http://dev.windows.com

• http://design.windows.com

• API Sites• http://www.restfulwebservices.net• http://developer.mashery.com/apis• http://www.programmableweb.com