毕业论文外文文献翻译Android-ApplicationFundamentals安卓应用基础.doc

毕业论文外文文献翻译Android-ApplicationFundamentals安卓应用基础.doc

《毕业论文外文文献翻译Android-ApplicationFundamentals安卓应用基础.doc》由会员分享，可在线阅读，更多相关《毕业论文外文文献翻译Android-ApplicationFundamentals安卓应用基础.doc（24页珍藏版）》请在冰豆网上搜索。

毕业设计（论文）

外文文献翻译

文献、资料中文题目：

安卓应用基础

文献、资料英文题目：

AndroidApplicationFundamentals

文献、资料来源：

文献、资料发表（出版）日期：

院（部）：

专业：

班级：

姓名：

学号：

指导教师：

翻译日期：

2017.02.14

外文及翻译

英语原文

AndroidApplicationFundamentals

AndroidapplicationsarewrittenintheJavaprogramminglanguage.TheAndroidSDKtoolscompilethecode—alongwithanydataandresourcefiles—intoan Androidpackage,anarchivefilewithan .apk suffix.Allthecodeinasingle .apk fileisconsideredtobeoneapplicationandisthefilethatAndroid-powereddevicesusetoinstalltheapplication.

Onceinstalledonadevice,eachAndroidapplicationlivesinitsownsecuritysandbox:

lTheAndroidoperatingsystemisamulti-userLinuxsysteminwhicheachapplicationisadifferentuser.

lBydefault,thesystemassignseachapplicationauniqueLinuxuserID（theIDisusedonlybythesystemandisunknowntotheapplication）.ThesystemsetspermissionsforallthefilesinanapplicationsothatonlytheuserIDassignedtothatapplicationcanaccessthem.

lEachprocesshasitsownvirtualmachine（VM）,soanapplication'scoderunsinisolationfromotherapplications.

lBydefault,everyapplicationrunsinitsownLinuxprocess.Androidstartstheprocesswhenanyoftheapplication'scomponentsneedtobeexecuted,thenshutsdowntheprocesswhenit'snolongerneededorwhenthesystemmustrecovermemoryforotherapplications.

Inthisway,theAndroidsystemimplementsthe principleofleastprivilege.Thatis,eachapplication,bydefault,hasaccessonlytothecomponentsthatitrequirestodoitsworkandnomore.Thiscreatesaverysecureenvironmentinwhichanapplicationcannotaccesspartsofthesystemforwhichitisnotgivenpermission.

However,therearewaysforanapplicationtosharedatawithotherapplicationsandforanapplicationtoaccesssystemservices:

lIt'spossibletoarrangefortwoapplicationstosharethesameLinuxuserID,inwhichcasetheyareabletoaccesseachother'sfiles.Toconservesystemresources,applicationswiththesameuserIDcanalsoarrangetoruninthesameLinuxprocessandsharethesameVM（theapplicationsmustalsobesignedwiththesamecertificate）.

lAnapplicationcanrequestpermissiontoaccessdevicedatasuchastheuser'scontacts,SMSmessages,themountablestorage（SDcard）,camera,Bluetooth,andmore.Allapplicationpermissionsmustbegrantedbytheuseratinstalltime.

ThatcoversthebasicsregardinghowanAndroidapplicationexistswithinthesystem.Therestofthisdocumentintroducesyouto:

lThecoreframeworkcomponentsthatdefineyourapplication.

lThemanifestfileinwhichyoudeclarecomponentsandrequireddevicefeaturesforyourapplication.

lResourcesthatareseparatefromtheapplicationcodeandallowyourapplicationtogracefullyoptimizeitsbehaviorforavarietyofdeviceconfigurations.

ApplicationComponents

ApplicationcomponentsaretheessentialbuildingblocksofanAndroidapplication.Eachcomponentisadifferentpointthroughwhichthesystemcanenteryourapplication.Notallcomponentsareactualentrypointsfortheuserandsomedependoneachother,buteachoneexistsasitsownentityandplaysaspecificrole—eachoneisauniquebuildingblockthathelpsdefineyourapplication'soverallbehavior.

Therearefourdifferenttypesofapplicationcomponents.Eachtypeservesadistinctpurposeandhasadistinctlifecyclethatdefineshowthecomponentiscreatedanddestroyed.

Herearethefourtypesofapplicationcomponents:

Activities

An activity representsasinglescreenwithauserinterface.Forexample,anemailapplicationmighthaveoneactivitythatshowsalistofnewemails,anotheractivitytocomposeanemail,andanotheractivityforreadingemails.Althoughtheactivitiesworktogethertoformacohesiveuserexperienceintheemailapplication,eachoneisindependentoftheothers.Assuch,adifferentapplicationcanstartanyoneoftheseactivities（iftheemailapplicationallowsit）.Forexample,acameraapplicationcanstarttheactivityintheemailapplicationthatcomposesnewmail,inorderfortheusertoshareapicture.

Anactivityisimplementedasasubclassof Activity andyoucanlearnmoreaboutitinthe Activities developerguide.

Services

A service isacomponentthatrunsinthebackgroundtoperformlong-runningoperationsortoperformworkforremoteprocesses.Aservicedoesnotprovideauserinterface.Forexample,aservicemightplaymusicinthebackgroundwhiletheuserisinadifferentapplication,oritmightfetchdataoverthenetworkwithoutblockinguserinteractionwithanactivity.Anothercomponent,suchasanactivity,canstarttheserviceandletitrunorbindtoitinordertointeractwithit.

Aserviceisimplementedasasubc