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1、毕业论文5000字英文翻译怎么找啊篇一：毕业设计的5000字英文文献翻译外文及翻译英语原文AndroidApplicationFundamentalsAndroidapplicationsarewrittenintheJavaprogramminglanguage.TheAndroidSDKtoolscompilethecodealongwithanydataandresourcefilesintoanAndroidpackage,anarchivefilewithan.apksuffix.Allthecodeinasingle.apkfileisconsideredtobeoneapplic
2、ationandisthefilethatAndroid-powereddevicesusetoinstalltheapplication.Onceinstalledonadevice,eachAndroidapplicationlivesinitsownsecuritysandbox:?TheAndroidoperatingsystemisamulti-userLinuxsysteminwhicheachapplicationisadifferentuser.?Bydefault,thesystemassignseachapplicationauniqueLinuxuserID(theIDi
3、susedonlybythesystemandisunknowntotheapplication).ThesystemsetspermissionsforallthefilesinanapplicationsothatonlytheuserIDassignedtothatapplicationcanaccessthem.?Eachprocesshasitsownvirtualmachine(VM),soanapplicationscoderunsinisolationfromotherapplications.?Bydefault,everyapplicationrunsinitsownLin
4、uxprocess.Androidstartstheprocesswhenanyoftheapplicationscomponentsneedtobeexecuted,thenshutsdowntheprocesswhenitsnolongerneededorwhenthesystemmustrecovermemoryforotherapplications.Inthisway,theAndroidsystemimplementstheprincipleofleastprivilege.Thatis,eachapplication,bydefault,hasaccessonlytothecom
5、ponentsthatitrequirestodoitsworkandnomore.Thiscreatesaverysecureenvironmentinwhichanapplicationcannotaccesspartsofthesystemforwhichitisnotgivenpermission.However,therearewaysforanapplicationtosharedatawithotherapplicationsandforanapplicationtoaccesssystemservices:?Itspossibletoarrangefortwoapplicati
6、onstosharethesameLinuxuserID,inwhichcasetheyareabletoaccesseachothersfiles.Toconservesystemresources,applicationswiththesameuserIDcanalsoarrangetoruninthesameLinuxprocessandsharethesameVM(theapplicationsmustalsobesignedwiththesamecertificate).?Anapplicationcanrequestpermissiontoaccessdevicedatasucha
7、stheuserscontacts,SMSmessages,themountablestorage(SDcard),camera,Bluetooth,andmore.Allapplicationpermissionsmustbegrantedbytheuseratinstalltime.ThatcoversthebasicsregardinghowanAndroidapplicationexistswithinthesystem.Therestofthisdocumentintroducesyouto:?Thecoreframeworkcomponentsthatdefineyourappli
8、cation.?Themanifestfileinwhichyoudeclarecomponentsandrequireddevicefeaturesforyourapplication.?Resourcesthatareseparatefromtheapplicationcodeandallowyourapplicationtogracefullyoptimizeitsbehaviorforavarietyofdeviceconfigurations.ApplicationComponentsApplicationcomponentsaretheessentialbuildingblocks
9、ofanAndroidapplication.Eachcomponentisadifferentpointthroughwhichthesystemcanenteryourapplication.Notallcomponentsareactualentrypointsfortheuserandsomedependoneachother,buteachoneexistsasitsownentityandplaysaspecificroleeachoneisauniquebuildingblockthathelpsdefineyourapplicationsoverallbehavior.Ther
10、earefourdifferenttypesofapplicationcomponents.Eachtypeservesadistinctpurposeandhasadistinctlifecyclethatdefineshowthecomponentiscreatedanddestroyed.Herearethefourtypesofapplicationcomponents:ActivitiesAnactivityrepresentsasinglescreenwithauserinterface.Forexample,anemailapplicationmighthaveoneactivi
11、tythatshowsalistofnewemails,anotheractivitytocomposeanemail,andanotheractivityforreadingemails.Althoughtheactivitiesworktogethertoformacohesiveuserexperienceintheemailapplication,eachoneisindependentoftheothers.Assuch,adifferentapplicationcanstartanyoneofthese共21页第1页activities(iftheemailapplicationa
12、llowsit).Forexample,acameraapplicationcanstarttheactivityintheemailapplicationthatcomposesnewmail,inorderfortheusertoshareapicture.AnactivityisimplementedasasubclassofActivityandyoucanlearnmoreaboutitintheActivitiesdeveloperguide.ServicesAserviceisacomponentthatrunsinthebackgroundtoperformlong-runni
13、ngoperationsortoperformworkforremoteprocesses.Aservicedoesnotprovideauserinterface.Forexample,aservicemightplaymusicinthebackgroundwhiletheuserisinadifferentapplication,oritmightfetchdataoverthenetworkwithoutblockinguserinteractionwithanactivity.Anothercomponent,suchasanactivity,canstarttheservicean
14、dletitrunorbindtoitinordertointeractwithit.AserviceisimplementedasasubclassofServiceandyoucanlearnmoreaboutitintheServicesdeveloperguide.ContentprovidersAcontentprovidermanagesasharedsetofapplicationdata.Youcanstorethedatainthefilesystem,anSQLitedatabase,ontheweb,oranyotherpersistentstoragelocationy
15、ourapplicationcanaccess.Throughthecontentprovider,otherapplicationscanqueryorevenmodifythedata(ifthecontentproviderallowsit).Forexample,theAndroidsystemprovidesacontentproviderthatmanagestheuserscontactinformation.Assuch,anyapplicationwiththeproperpermissionscanquerypartofthecontentprovider(suchasCo
16、ntactsContract.Data)toreadandwriteinformationaboutaparticularperson.Contentprovidersarealsousefulforreadingandwritingdatathatisprivatetoyourapplicationandnotshared.Forexample,theNotePadsampleapplicationusesacontentprovidertosavenotes.AcontentproviderisimplementedasasubclassofContentProviderandmustimplementastandardsetofAPIsthatenableotherapplicationstoperformtransactions.Formoreinformation,seetheContentPro
