外文文献The basic of description of android system对Android系统的基本描诉.docx
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外文文献The basic of description of android system对Android系统的基本描诉.docx
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外文文献Thebasicofdescriptionofandroidsystem对Android系统的基本描诉
外文文献-Thebasicofdescriptionofandroidsystem对Android系统的基本描诉
毕业设计外文文献原文及译文
Thebasicofdescriptionofandroidsystem
对Android系统的基本描诉
学生姓名:
学号:
电子与计算机科学技术系系别:
计算机科学与技术专业:
指导教师:
2015年5月
2015届毕业设计外文文献原文及译文
Thebasicofdescriptionofandroidsystem
BytheOpenMobileAlliance(openHandsetAllianceledbyGoogle)developedtheandroidsystemisawidelyoptimisticaboutanopensourcephonesystem,thesystemprovidesabasicoperatingsystem,amiddlewareapplicationlayer,ajavadevelopmenttoolsandasystemApplicationcollector(collectionofsystemapplications).
TheandroidtheSDKsince2007onthereleaseofthefirstandroidphoneinOctober2008beforethebirth.Googleopenedsincethenonhisowntime,Taiwan'sHTC,themanufactureroftheT-MobileG1estimateG1shipmentshavemorethanonemillionattheendof2008.AccordingtoindustryinsidersexpecttheG1mobilephonesalesin2009continue.Manyothermobilephonesuppliersinthenearfutureplanstosupportthissystem.
Aroundanandroidandahugedevelopercommunityhasbeenestablished,whilealotofnewproductsandapplicationsontheandroid.Android'smainsellingpointisthatitenablesdeveloperstoseamlesslyexpandonlineservicestomobilephones.CalendarandContactsWebapplicationsthroughthesystem.Usersonlyneedtoprovideanandroidusernameandpassword,thephoneautomaticallysyncwithGoogleservices.Theothervendorsarequicklyadapttheirexistinginstantmessaging,socialnetworkingandgamingservices.Androidandmanycompaniesfindnewwaystointegratetheirexistingbusinesstotheandroid.
Traditionaldesktopandserveroperatingsystemhasbeenworkingfortheintegrationofsecurityfeatures.Theseindividualsandbusinessapplicationsonasingleplatformisverygood,howeverabusinessphoneplatformlikeandroidisnotveryuseful.Itgivesthehopeofmanyresearchers.Androidisnotparkedinthebodyforotherplatformapplicationsupport:
theimplementationoftheapplicationdependsonatop-levelJAVAmiddleware,themiddlewarerunningontheembeddedLinuxkernel.Therefore,developersshoulddeploytheirapplicationstotheAndroidmustuseacustomuserinterfaceenvironment.
Inaddition,theandroidsystemapplicationslimittheapplicationtocalleachotherAPI.
Althoughtheseapplicationshavecertainsafetyfeatures,someofourexperienceddeveloperstocreateAndroidapplicationswhorevealedthatthedesignofsecurity
2015届毕业设计外文文献原文及译文
applicationsisnotalwaysstraightforward.Androidusesasimplepermissionlabeldistributionmodetorestrictaccesstoresources,butthereasonsforthenecessityandconvenienceofotherapplications,thedesignershaveincreasedtheconfusiononthissystem.ThispaperattemptstoexplainthecomplexityoftheAndroidsecurity,andpayattentiontosomeofthepossibledevelopmentdefectsandapplicationsecurity.Wetrytodrawsomelessonslearned,andhopethatthesafetyofthefuture.
Androidapplicationframeworkfordevelopersisamandatoryframework.Itdoesnothaveamain()functionfunctionorasingleentrypointfortheimplementationofthecontrary,thedevelopermustinthedesignofapplicationcomponents.WedevelopedapplicationstohelptheAPIoftheandroidSDK.TheAndroidsystemdefinesfourkindsofcomponenttype.
Activitycomponentthatdefinestheapplicationuserinterface.Usually,theapplicationdeveloperdefineseachactivityscreen.Activitycanstart,itmaypassandreturnvalues.CanbehandledatatimeonlyakeyboardsystemActivity,allotherActivitywillbesuspendedatthistime.
Servicecomponentsperformbackgroundprocessing.Theneedforsomeoperationswhenanactivity,afterthedisappearanceoftheuserinterface(suchasdownloadingafileorplayingmusic),itusuallytakesuchactionspeciallydesignedservices.Developerscanalsouseaspecialdaemonatsystemstartup,theserviceisusuallydefinedaremoteprocedurecall(RPC),andothersystemcomponentscanbeusedtosendtheinterfacecommandandretrievedata,aswellastoregisteracallbackfunction.
ContentProvidercomponentstorageandsharedatawithrelationaldatabaseinterfaces.EachContentsupplierhasanassociated"rights"todescribeitscontentscontains.OthercomponentswhenusedasahandletoexecuteSQLqueries(forexampleSELECT,INSERT,
orDELETEcontent.Contentsuppliersaretypicallystoredthevaluesonthedatabaserecords,dataretrievalisaspecialcase,thefileisalsosharedbythecontentproviderinterface.
Thecomponentsofthebroadcastreceiverastosendamessagefromthemailboxtotheapplication.Typically,thebroadcastmessage,theapplicationcodeimplicitdestination.
2015届毕业设计外文文献原文及译文
Therefore,theradioreceiversubscribetothesedestinationsreceivemessagessenttoit.Theapplicationcodecanalsobesolvedexplicitlybroadcastreceivers,includingthenamespaceallocation.
ThemainmechanismoftheinteractionofthecomponentsoftheComponentInteraction,isanintent,whichisasimplemessageobject,whichcontainsadestinationaddressanddatacomponents.TheAndroidAPIdefineshisapproachintointent,andusethatinformationtoinitiateanactivity.suchasstartanactivity(startActivity(Anintent))startservices(thestartService(Anintent))andradio(sendBroadcast(Anintent)).Androidframeworktoinformthecallstothesemethodsbegantoperforminthetargetapplicationcode.Thisprocess,theinternalcomponentsofcommunicationiscalledanaction.Simplyput,theIntentobjectdefinedinthe"Intenttoimplementthe"action".OneofthemostpowerfulfeaturesoftheAndroidisallowedavarietyofintentaddressingmechanism.Thedevelopercansolvethespaceofatargetcomponentusingitsapplications,theycanalsospecifyanimplicitname.Inthelattercase,thesystemdeterminesthebestcomponentsofanactionbyconsideringtheinstalledapplicationsanduserchoice.
AndroidapplicationsarewrittenintheJavaprogramminglanguage.ThecompiledJavacode—alongwithanydataandresourcefilesrequiredbytheapplication—isbundledby
theapttoolintoanAndroidpackage,anarchivefilemarkedbyan.Asuffix.Thisfileisthevehiclefordistributingtheapplicationandinstallingitonmobiledevices;it'sthefileusersdownloadtotheirdevices.Allthecodeinasingle.APKfileisconsideredtobeoneapplication.
Inmanyways,eachAndroidapplicationlivesinitsownworld:
(1)Bydefault,everyapplicationrunsinitsownLinuxprocess.Androidstartstheprocesswhenanyoftheapplication'scodeneedstobeexecuted,andshutsdowntheprocesswhenit'snolongerneededandsystemresourcesarerequiredbyotherapplications.
(2)Eachprocesshasitsownvirtualmachine(VM),soapplicationcoderunsinisolationfromthecodeofallotherapplications.
2015届毕业设计外文文献原文及译文
(3)Bydefault,eachapplicationisassignedauniqueLinuxuserID.Permissionsaresetsothattheapplication'sfilesarevisibleonlytothatuserandonlytotheapplicationitselftherearewaystoexportthemtootherapplicationsaswell.
ApplicationComponents
AcentralfeatureofAndroidisthatoneapplicationcanmakeuseofelementsofotherapplication(providedthoseapplicationpermitit).Forexample,ifyourapplicationneedstodisplayascrollinglistofimagesandanotherapplicationhasdevelopedasuitableandmadeitavailabletoothers,youcancalluponthattodothework,ratherthandevelopyourown.Yourapplicationdoesn'tincorporatethecodeoftheotherapplicationorlinktoit.Rather,itsimplystartsupthatpieceoftheotherapplicationwhentheneedarises.Forthistowork,thesystemmustbeabletostartanapplicationprocesswhenanypartofitisneeded,andinstantiatetheJavaobjectsforthatpart.Therefore,unlikeapplicationsonmostothersystems,Androidapplicationsdon'thaveasingleentrypointforeverythingintheapplication(nomain()function,forexample).Rather,theyhaveessentialcomponentsthatthesystemcaninstantiateandrunasneeded.Therearefourtypesofcomponents:
Activities
Anactivitypresentsavisualuserinterfaceforonefocusedendeavortheusercanundertake.Forexample,anactivitymightpresentalistofmenuitemsuserscanchoosefromoritmightdisplayphotographsalongwiththeircaptions.Atextmessagingapplicationmighthaveoneactivitythatshowsalistofcontactstosendmessagesto,asecondactivitytowritethemessagetothechosencontact,andotheractivitiestoreviewoldmessagesorchangeorchangesettings.Toughtheyworktogethertoformacohesiveuserinterface,eachactivityisindependentoftheothers.EachoneisimplementedasasubclassoftheActivitybaseclass.
Anapplicationmightconsistofjustoneactivityor,likethetextmessagingapplicationjustmentioned,itmaycontainseveral.Whattheactivitiesare,andhowmanytherearedepends,ofcourse,ontheapplicationanditsdesign.Typically,oneoftheactivitiesismarkedasthefirstonethatshouldbepresentedtotheuserwhentheapplicationislaunched.Moving
2015届毕业设计外文文献原文及译文
fromoneactivitytoanotherisaccomplishedbyhavingthecurrentactivitystartthenextone.
Eachactivityisgivenadefaultwindowtodrawin.Typically,thewindowfillsthescreen,butitmightbesmallerthanthescreenandfloatontopofotherwindows.Anactivitycanalsomakeuseofadditionalwindows—forexample,apop-updialogthatcallsforauser
responseinthemidstoftheactivity,orawindowthatpresentsuserswithvitalinformationwhentheyselectaparticularitemon-screen.Thevisualcontentofthewindowisprovidedbyahierarchyofviews—obj
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