外文翻译安卓系统的基本描述Word格式.docx

外文翻译安卓系统的基本描述Word格式.docx

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BytheOpenMobileAlliance（openHandsetAllianceledbyGoogle）developedtheandroidsystemisawidelyoptimisticaboutanopensourcephonesystem,thesystemprovidesabasicoperatingsystem,amiddlewareapplicationlayer,ajavadevelopmenttoolsandasystemApplicationcollector（collectionofsystemapplications）.TheandroidtheSDKsince2007onthereleaseofthefirstandroidphoneinOctober2008beforethebirth.Googleopenedsincethenonhisowntime,Taiwan'

sHTC,themanufactureroftheT-MobileG1estimateG1shipmentshavemorethanonemillionattheendof2008.AccordingtoindustryinsidersexpecttheG1mobilephonesalesin2009continue.Manyothermobilephonesuppliersinthenearfutureplanstosupportthissystem.

Aroundanandroidandahugedevelopercommunityhasbeenestablished,whilealotofnewproductsandapplicationsontheandroid.Android'

smainsellingpointisthatitenablesdeveloperstoseamlesslyexpandonlineservicestomobilephones.ThisisthemostobviousexampleisGoogle'

stightlyintegratedwithGmail,CalendarandContactsWebapplicationsthroughthesystem.Usersonlyneedtoprovideanandroidusernameandpassword,thephoneautomaticallysyncwithGoogleservices.Theothervendorsarequicklyadapttheirexistinginstantmessaging,socialnetworkingandgamingservices.Androidandmanycompaniesfindnewwaystointegratetheirexistingbusinesstotheandroid.

Traditionaldesktopandserveroperatingsystemhasbeenworkingfortheintegrationofsecurityfeatures.Theseindividualsandbusinessapplicationsonasingleplatformisverygood,howeverabusinessphoneplatformlikeandroidisnotveryuseful.Itgivesthehopeofmanyresearchers.Androidisnotparkedinthebodyforotherplatformapplicationsupport:

theimplementationoftheapplicationdependsonatop-levelJAVAmiddleware,themiddlewarerunningontheembeddedLinuxkernel.Therefore,developersshoulddeploytheirapplicationstotheAndroidmustuseacustomuserinterfaceenvironment.

Inaddition,theandroidsystemapplicationslimittheapplicationtocalleachotherAPIcollaboration,andtheothertoauthenticatetheuserapplication.Althoughtheseapplicationshavecertainsafetyfeatures,someofourexperienceddeveloperstocreateAndroidapplicationswhorevealedthatthedesignofsecurityapplicationsisnotalwaysstraightforward.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（egSELECT,INSERT,orDELETEcontent.Contentsuppliersaretypicallystoredthevalues​​onthedatabaserecords,dataretrievalisaspecialcase,thefileisalsosharedbythecontentproviderinterface.

Thecomponentsofthebroadcastreceiverastosendamessagefromthemailboxtotheapplication.Typically,thebroadcastmessage,theapplicationcodeimplicitdestination.Therefore,theradioreceiversubscribetothesedestinationsreceivemessagessenttoit.Theapplicationcodecanalsobesolvedexplicitlybroadcastreceivers,includingthenamespaceallocation.

ThemainmechanismoftheinteractionofthecomponentsoftheComponentInteraction,isanintent,whichisasimplemessageobject,whichcontainsadestinationaddressanddatacomponents.TheAndroidAPIdefineshisapproachintointent,andusethatinformationtoinitiateanactivitysuchasstartanactivity（startActivity（Anintent））startservices（thestartService（Anintent））andradio（sendBroadcast（Anintent））.Androidframeworktoinformthecallstothesemethodsbegantoperforminthetargetapplicationcode.Thisprocess,theinternalcomponentsofcommunicationiscalledanaction.Simplyput,theIntentobjectdefinedinthe"

Intenttoimplementthe"

action"

.OneofthemostpowerfulfeaturesoftheAndroidisallowedavarietyofintentaddressingmechanism.Thedevelopercansolvethespaceofatargetcomponentusingitsapplications,theycanalsospecifyanimplicitname.Inthelattercase,thesystemdeterminesthebestcomponentsofanactionbyconsideringtheinstalledapplicationsanduserchoice.

Implicitnameiscalledtheactionstringbecauseofhisspecialtypeoftherequestedaction.Suchasaviewactionstring,inanintentdatafieldpointstoanimagefile,thesystemwilldirectlyreferringtothepreferredimageviewer.

Developerscanalsousetheactionstringalargenumberofradiotosendandreceive.Receiveratthereceivingend,thedevelopersuseanintentfiltertocustomizethespecialactionstring.AndroidDepartment,includingtheadditionalgoaloftheresolutionrules,butanoptionalstringtypeofdatamanipulationisthemostcommon.

AndroidapplicationsarewrittenintheJavaprogramminglanguage.ThecompiledJavacode—alongwithanydataandresourcefilesrequiredbytheapplication—isbundledbytheapttoolintoanAndroidpackage,anarchivefilemarkedbyan.apksuffix.Thisfileisthevehiclefordistributingtheapplicationandinstallingitonmobiledevices;

it'

sthefileusersdownloadtotheirdevices.Allthecodeinasingle.apkfileisconsideredtobeoneapplication.

Inmanyways,eachAndroidapplicationlivesinitsownworld:

（1）Bydefault,everyapplicationrunsinitsownLinuxprocess.Androidstartstheprocesswhenanyoftheapplication'

scodeneedstobeexecuted,andshutsdowntheprocesswhenit'

snolongerneededandsystemresourcesarerequiredbyotherapplications.

（2）Eachprocesshasitsownvirtualmachine（VM）,soapplicationcoderunsinisolationfromthecodeofallotherapplications.

（3）Bydefault,eachapplicationisassignedauniqueLinuxuserID.Permissionsaresetsothattheapplication'

sfilesarevisibleonlytothatuserandonlytotheapplicationitself—altoughtherearewaystoexportthemtootherapplicationsaswell.

It'

spossibletoarrangefortwoapplicationstosharethesameuserID,inwhilecasetheywillbeabletoseeeachother'

sfiles.Toconservesystemresources,applicationswiththesameIDcanalsoarrangetoruninthesameLinuxprocess,sharingthesameVM.

ApplicationComponents

AcentralfeatureofAndroidisthatoneapplicationcanmakeuseofelementsofotherapplication（providedthoseapplicationpermitit）.Forexample,ifyourapplicationneedstodisplayascrollinglistofimagesandanotherapplicationhasdevelopedasuitablescrollerandmadeitavailabletoothers,youcancalluponthatscrollertodothework,ratherthandevelopyourown.Yourapplicationdoesn'

tincorporatethecodeoftheotherapplicationorlinktoit.Rather,itsimplystartsupthatpieceoftheotherapplicationwhentheneedarises.

Forthistowork,thesystemmustbeabletostartanapplicationprocesswhenanypartofitisneeded,andinstantiatetheJavaobjectsforthatpart.Therefore,unlikeapplicationsonmostothersystems,Androidapplicationsdon'

thaveasingleentrypointforeverythingintheapplication（nomain（）function,forexample）.Rather,theyhaveessentialcomponentsthatthesystemcaninstantiateandrunasneeded.Therearefourtypesofcomponents:

Activities

Anactivitypresentsavisualuserinterfaceforonefocusedendeavortheusercanundertake.Forexample,anactivitymightpresentalistofmenuitemsuserscanchoosefromoritmightdisplayphotographsalongwiththeircaptions.Atextmessagingapplicationmighthaveoneactivitythatshowsalistofcontactstosendmessagesto,asecondactivitytowritethemessagetothechosencontact,andotheractivitiestoreviewold