j2me best practices and patterns

《j2me best practices and patterns》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。

1、Chapter4J2MEBestPracticesandPatterns71P:10CompCompRef8710-9ch04.vpThursday,February06,200312:01:12PM72J2ME:TheCompleteReferenceesigningapplicationsforsmallcomputingdevicesisachallenge,tosaytheleast,primarilybecauseofthelimitedresourcesfoundinthesedevices.Youmus

2、tassumeDthatthesmallcomputingdevicecontainsminimalmemoryandstorageroomforpersistentdata,asdiscussedinthefirsttwochaptersofthisbook.Manytraditionalsystemsdesignmethodsandbestpracticesaresimplynotappropriateforbuildingapplicationstorunonsmallcomputingdevices.Thismeans

3、thatyoumustrethinkyourapproachtodesigninganapplicationearmarkedforasmallcomputingdevice.Fortunately,therearebestpracticesandpatternsthatyoucanimplementinyourdesignthatovercomemanylimitationsinherentinsmallcomputingdevices.Inthischapteryou’lllearnaboutbestpracticesan

4、dpatternsfordevelopingJ2MEapplications.TheRealityofWorkinginaJ2MEWorldAsmallcomputingdevicehasaradicallydifferenthardwareconfigurationthantraditionalcomputingdevicessuchasdesktopcomputersandservers.Itisforthisreasonthatyoumusttakeintoaccountthedevice’shardwareconfig

5、urationwhendesigningyourJ2MEapplication.Considerthefollowingdifferencesbetweentraditionalcomputingdevicesandsmallcomputingdevices.Traditionalcomputingdevicesareundercontinuouspowerfromthepowergrid,whilesomesmallcomputingdevicessuchascellulartelephonesrelyonbatterypo

6、werthatdiminishesduringthecourseofoperation.Apowergridpowersothersmallcomputingdevicessuchasset-topboxesandappliances.Anotherimportantdifferencebetweentraditionalcomputingdevicesandsmallcomputingdevicesisthenetworkconnection.Unliketraditionalcomputingdevices,mobiles

7、mallcomputingdevicesconnecttoanetworkviaaradioorinfraredconnectionwhosequalityvariesdependingonthedistanceofthedevicefromanetworkreceiverandthestrengthofthesignalgeneratedbythedevice.Somenonmobilesmallcomputingdevicessuchasset-topboxesuseahard-wirednetworkconnection

8、similartotraditionalcomputingdevices.Inconsistencyinanetworkconnectionandthediminishinglongevityofpowertypicallyrequiretheuserofasmallcomp