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1、1.AppComponents:ApplicationFundamentals(程序基本面):QUICKVIEW:·Androidapplicationsarecomposed(组成)ofoneormoreapplicationcomponents(activities,services,contentproviders,andbroadcastreceivers)·Eachcomponentperforms(执行)adifferentroleintheoverall(全部)applicationbehavior,and
2、eachonecanbeactivatedindividually(个别的)(evenbyotherapplications)·Themanifestfilemustdeclareallcomponentsintheapplicationandshouldalsodeclareallapplicationrequirements,suchastheminimumversionofAndroidrequiredandanyhardwareconfigurationsrequired·Non-codeapplicationr
3、esources(images,strings,layoutfiles,etc.)shouldincludealternatives(替代选择)fordifferentdeviceconfigurations(suchasdifferentstringsfordifferentlanguagesanddifferentlayoutsfordifferentscreensizes)·Anapplicationcanrequestpermissiontoaccessdevicedatasuchastheuser'sconta
4、cts,SMSmessages,themountablestorage(SDcard),camera,Bluetooth,andmore.Allapplicationpermissionsmustbegranted(同意)bytheuseratinstalltime.ApplicationComponents(程序组件):Herearethefourtypesofapplicationcomponents:Activities·An activity represents(表现)asinglescreenwithause
5、rinterface(界面).Forexample,anemailapplicationmighthaveoneactivitythatshowsalistofnewemails,anotheractivitytocompose(构成)anemail,andanotheractivityforreadingemails.Althoughtheactivitiesworktogethertoformacohesiveuserexperienceintheemailapplication,eachoneisindepende
6、ntoftheothers.Assuch,adifferentapplicationcanstartanyoneoftheseactivities(iftheemailapplicationallowsit).Forexample,acameraapplicationcanstarttheactivityintheemailapplicationthatcomposesnewmail,inorderfortheusertoshareapicture.·Anactivityisimplementedasasubclasso
7、f Activity andyoucanlearnmoreaboutitinthe Activitiesdeveloperguide.Services·A service isacomponentthatrunsinthebackgroundtoperform(执行)long-runningoperationsortoperformworkforremoteprocesses.Aservicedoesnotprovideauserinterface.Forexample,aservicemightplaymusicint
8、hebackgroundwhiletheuserisinadifferentapplication,oritmightfetch(取数据)dataoverthenetworkwithoutblockinguserinteractionwithanactivity.Anothercomponent,suchasanac
