CS4720

MobileDeviceArchitecture

CS4720– MobileApplicationDevelopment

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TheWayBackTime• Whenaphonewasaphone…• Plusastory!

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Ohyes…thiswasaphone…

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TheMotorolaDynaTAC 8000X• 1983• 13x1.75x3.5• 2.5pounds• $3,995• +MonthlyFee• +Payperminute

Thentherewasthebagphone…

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NokiaInventsMobilePhoneGaming!• ObviouslyI’mtalkingabouttheN-Gage!• …• Okay,rememberSnakeontheoldNokiaphones?

• Otherearlyappsinclude:basiccontactapps,Pong,andTetris

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Third-PartyAppsBegin• Mobilephonesstoppedbeinganovelty• Batteriesgotbetter,formfactorsimproved,coverageimproved,planswere…better…

• Thehandsetmanufacturersdidn’twanttowritealltheapplicationsforthesenewphones

• However…theydidn’twanttoopenuptheirplatform…

• Thefirstmobilewebplatformwasborn

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WAP• WirelessApplicationProtocol• Basicallyit’sastripped-downHTTPthatwasmeanttobebetterattransmittingovertheunreliablemobilenetwork

• WAPusedWMLinsteadofHTML–useda“card”mentality

• TwopopularWAPsites?CNNandESPN

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In-AppPurchasesBeforeApps• SMS…

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Whendiditallchange?• WiththeInternetfullofimagesandmedia…• Andotherhandhelddevicessellinglikegangbusters(GameBoy)…

• Whatchangedwithphones?• Phonesstartedrunningknownoperatingsystems(WindowsCEandLinux)

• Nowbiggerplayerswereinvolved,andhandsetmanufacturesdecidedtoopenup

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Andwhat’shappenedsince?• Themobilemarketisseriouslyfractured• Whodoyoudevelopfor?• HowdoyoutestforEVERYphone?• Whichmarketworksbest?• Howdoyouportyourappbetweenplatforms?• Whichtoolsdoyouuse?Canyouuse?

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AndNowGoogle• TheOpenHandsetAllianceisanattempttoeffectively“geteveryoneonthesamepage”

• OpenSource• FamiliarEnvironmentsandTools• SecureOS(Linuxw/appsigning)• NoRoyaltiesorDeveloperFees

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TheThree-TieredArchitecture

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TheThree-TieredArchitecture• Forawebapplication…

– Thebrowser+dynamicallygeneratedHTMListhepresentationlayer

– Middlewarefiles(function-specificPHP,JavaservletsonTomcat)containthebusinesslogic

– Thedatabaseserveristhedatalayer

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It'snotnewstoyou• Theconceptsofthethree-tieredarchitectureapplytomanydesignscenarios– Keepthepresentationseparatesoit'slightweight,easiertomaintain,andcanbetestedseparately

– Keepthelogicseparatesoyoucanchangethelogicasneededwithouthavingtochangethepresentationtoomuch

– KeepthedataseparatebecauseyoushouldNEVERbuildasystembasedonthecurrentdatavalues

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Model-View-Controller• ThisisthedefinitionofwhatMVCis• TheMVCpatternmaps:

– Identifieswhattheuserisaskingfor– Loadsaparticularresource– Displaysthepertinentinfoaboutthatresourcebacktotheuser

• ToModel,Controller,View(inthatorder)

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MVC

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MVC

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Controller• Theroleofthecontrollerisbasicallytrafficcop• Ittakestherequestfromtheuserand(withtheassistanceoftheserverandroutingrules)turnsitintoamethodcallofsorts

• Itfindstheappropriatemodeltoload• Itfindstheappropriateviewtoload• Itreturnsthewholethingbacktotheuser

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Model• Themodelistherepresentationofthedata• Thismayormaynotbedirectlylinkedtoadatabase(butoftenisinlargerapps)

• AmodelisoftentranslateddirectlyintoaDBtable,withthecolumnsasitsattributes

• Think“classdefinitionw/DBbackend”• Oftencontainsrelationshiprules(aStudenthasmanyClasses,forinstance)

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View• Theclosestthingtowhatyou’vebeendealingwithsofaristheview

• It’seffectivelyanHTMLtemplatethatwillbepopulatedwiththeappropriatedatafromtheloadedmodel

• ItoftenhasPHP(orwhatever)embeddedinit• AllUIcomponentsgohere

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PuttingitallTogether• So,ifyouwerebuildingablog,whatmightsomeofthemodelsbe?

• Whataretheresourcesthatshouldhaveaddressestothem?

• Howdotheyrelatetoeachother?

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Non-shockeroftheday• Weneedtoconsiderthesamethingsforamobilearchitecture

• Why?Whataddedconcernsdowehavewhenweconsidermobileapplications?– PresentationLayerconcerns– LogicLayerconcerns– DataLayerconcerns

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MobileArchitectures

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• RichMobileArchitecture– Businessandsomedataservicesonthephoneitself– Goodforappsthathavetorun“offthegrid”

• ThinMobileArchitecture– Mostbusinessandalldataservicesontheserver– Goodforappsthatrequirephoneservices,butdoesrequireInternetconnectivity

• RichInternetApplication– Eschewstheuseofanyphoneresourcesotherthanabrowser

– Goodforappsthatcanrunonanythingwithabrowser

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Whicharewedoing?

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• RichInternetApplication– Well,it'scertainlynotthisone…whynot?

• RichapporThinapp?• Dobothfollowthethree-tieredarchitecturestructure?Whyorwhynot?

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RichMobileArchitecture

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ThePresentationLayer• Remember:it'saphone!

– Simple=good– Peoplehavedifferentsizedfingers– Useractionscallfunctionswhichexecutefeatures;useractions!=features

– Phonescanhavevaryingamountsofpower/resources

– Phonescanbeonoroffthecellulargridatanypoint

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PresentationApproach• Rememberyourclienttype• Determinehowyouwillpresentdatainacoherent,unifiedmethod

• Determinehowyouwillguardagainstuntrustedinput• Ensureyouhavefactoredoutyourbusinesslogic• Determinehowyouwillpassdatabetweenlayers(i.e.howyouwillcalltheservice,howyouwillgetmoreinfoaboutabuilding,etc)

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TheBusinessLayer• Forthemostpart,theseareyourwebservicesandrelatedfunctionalities– Eachofyourthreewebservicesyouareusing

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BusinessApproach• IdentifyFEATURESthatwillexistatthislevel• Buildcomponentsthatsupportafeature'sexecution

• Hideimplementationdetailsfromthepresentationlayer

• Determineif(how)youwillcacheinformationonthedevice

• Mapoutusecases

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TheDataLayer• Thiswillbeyourmodulethattalkstothedatabase

• Willbeintertwinedwiththebusinesslayertosomedegree

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DataApproach• Foreachfeature,determinewhatdataisrequired

• BuildSQLqueriesaroundthefeatures• Ensurethatyouareusingpreparedstatementstoguardagainstincorrectdataentry(orinjection)

• Determinehowyouwillmanageconnections• Determineifyouwillbatchupcommandsintoonebigcommand

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YourMobileArchitecture

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• YourApproach:• Android/iOS UIwhichcalls…

• …your “businesslogic”cope

• …thatconnectstosomedatastore(localorremote)

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TheAndroidArchitecture

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YourMainComponents• Activities– representasinglescreenwithaUI• Services– representsaprocessrunninginthebackground

• ContentProvider– alinkbacktothedata• BroadcastReceiver– listensforsystem-widemessagestorespondto

• Application– asetofActivitiesthatmakeupacohesiveunit

• Intent– amessagetobepassed33

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TheActivity

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TheIntent

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