Backward Compatibility for Applications 翻译

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1、BackwardCompatibilityforApplications应用的向后兼容AvarietyofAndroid-powereddevicesarenowavailabletoconsumersfromcarriersingeographiesaroundtheworld.Acrossthosedevices,arangeofAndroidplatformversionsareinuse,somerunningthelatestversionoftheplatform,othersrunningolderversions.Asadeveloper,youneedtoconsid

2、ertheapproachtobackwardcompatibilitythatyouwilltakeinyourapplication—doyouwanttoallowyourapplicationtorunonalldevices,orjustthoserunningthelatestsoftware?InsomecasesitwillbeusefultoemploythenewerAPIsondevicesthatsupportthem,whilecontinuingtosupportolderdevices.一种android-powered设备现在可以被全世界各地的消费者使用

3、。通过这个设备，一系列的android平台版本正在被使用，一些运行着最新的平台版本，另一些运行着比较老的版本。作为一个开发者，你需要为你的应用考虑一个向后兼容的途径，你想让你的应用能跑在所有的设备上，还是只能跑那些最新的软件？在一些情形下，在支持他们的设备上使用比较新的APIs对于继续支持较老的设备是相当有用的。SettingtheminSdkVersionIftheuseofanewAPIisintegraltotheapplication—perhapsyouneedtorecordvideousinganAPIintroducedinAndroid1.5(APILevel3)—y

4、oushouldaddatotheapplication'smanifest,toensureyourappwon'tbeinstalledonolderdevices.Forexample,ifyourapplicationdependsonanAPIintroducedinAPILevel3,youwouldspecify"3"asthevalueoftheminimumSDKversion:   ...    ... Ho

5、wever,ifyouwanttoaddausefulbutnon-essentialfeature,suchaspoppingupanon-screenkeyboardevenwhenahardwarekeyboardisavailable,youcanwriteyourprograminawaythatallowsittousethenewerfeatureswithoutfailingonolderdevices.UsingreflectionSupposethere'sasimplenewcallyouwanttouse,likeandroid.os.Debug.dumpHpr

6、ofData(Stringfilename).TheDebugclasshasexistedsinceAndroid1.0,butthemethodisnewinAnroid1.5(APILevel3).Ifyoutrytocallitdirectly,yourappwillfailtorunondevicesrunningAndroid1.1orearlier.Thesimplestwaytocallthemethodisthroughreflection.Thisrequiresdoingaone-timelookupandcachingtheresultinaMethodobje

7、ct.UsingthemethodisamatterofcallingMethod.invokeandun-boxingtheresult.Considerthefollowing:publicclassReflect{  privatestaticMethodmDebug_dumpHprofData;  static{    initCompatibility();  };  privatestaticvoidinitCompatibilit