安卓應(yīng)用基礎(chǔ)畢業(yè)論文外文翻譯

1、roidApplicationFundamentalsroidapplicationsarewrittenintheJavaprogramminglanguage.TheroidSDKtoolscompilethecode—alongwithanydataresourcefiles—intoanroidpackageanarchivefilewithan.apksuffix.Allthecodeinasingle.apkfileisco

2、nsideredtobeoneapplicationisthefilethatroidpowereddevicesusetoinstalltheapplication.Onceinstalledonadeviceeachroidapplicationlivesinitsownsecuritysbox:TheroidoperatingsystemisamultiuserLinuxsysteminwhicheachapplicationis

3、adifferentuser.BydefaultthesystemassignseachapplicationauniqueLinuxuserID(theIDisusedonlybythesystemisunknowntotheapplication).ThesystemsetspermissionsfallthefilesinanapplicationsothatonlytheuserIDassignedtothatapplicati

4、oncanaccessthem.Eachprocesshasitsownvirtualmachine(VM)soanapplicationscoderunsinisolationfromotherapplications.BydefaulteveryapplicationrunsinitsownLinuxprocess.roidstartstheprocesswhenanyoftheapplicationscomponentsneedt

5、obeexecutedthenshutsdowntheprocesswhenitsnolongerneededwhenthesystemmustrecovermemyfotherapplications.Inthiswaytheroidsystemimplementstheprincipleofleastprivilege.Thatiseachapplicationbydefaulthasaccessonlytothecomponent

6、sthatitrequirestodoitswknome.Thiscreatesaverysecureenvironmentinwhichanapplicationcannotaccesspartsofthesystemfwhichitisnotgivenpermission.Howevertherearewaysfanapplicationtosharedatawithotherapplicationsfanapplicationto

7、accesssystemservices:ItspossibletoarrangeftwoapplicationstosharethesameLinuxuserIDinwhichcasetheyareabletoaccesseachothersfiles.ToconservesystemresourcesapplicationswiththesameuserIDcanalsoarrangetoruninthesameLinuxproce

8、ssoneoftheseactivities(iftheemailapplicationallowsit).Fexampleacameraapplicationcanstarttheactivityintheemailapplicationthatcomposesnewmailinderftheusertoshareapicture.AnactivityisimplementedasasubclassofActivityyoucanle

9、arnmeaboutitintheActivitiesdeveloperguide.ServicesAserviceisacomponentthatrunsinthebackgroundtoperfmlongrunningoperationstoperfmwkfremoteprocesses.Aservicedoesnotprovideauserinterface.Fexampleaservicemightplaymusicintheb

10、ackgroundwhiletheuserisinadifferentapplicationitmightfetchdataoverthewkwithoutblockinguserinteractionwithanactivity.Anothercomponentsuchasanactivitycanstarttheserviceletitrunbindtoitindertointeractwithit.Aserviceisimplem

11、entedasasubclassofServiceyoucanlearnmeaboutitintheServicesdeveloperguide.ContentprovidersAcontentprovidermanagesasharedsetofapplicationdata.YoucanstethedatainthefilesystemanSQLitedatabaseonthewebanyotherpersistentstagelo

12、cationyourapplicationcanaccess.Throughthecontentproviderotherapplicationscanqueryevenmodifythedata(ifthecontentproviderallowsit).Fexampletheroidsystemprovidesacontentproviderthatmanagestheuserscontactinfmation.Assuchanya

13、pplicationwiththeproperpermissionscanquerypartofthecontentprovider(suchasContactsContract.Data)toreadwriteinfmationaboutaparticularperson.Contentprovidersarealsousefulfreadingwritingdatathatisprivatetoyourapplicationnots

14、hared.FexampletheNotePadsampleapplicationusesacontentprovidertosavenotes.AcontentproviderisimplementedasasubclassofContentProvidermustimplementastardsetofAPIsthatenableotherapplicationstoperfmtransactions.Fmeinfmationsee