Android ---Check System Version at Runtime（在软件运行时检查判断系统版本）

Android为我们提供了一个常量类Build，其中最主要是Build中的两个内部类VERSION和VERSION_CODES

VERSION表示当前系统版本的信息，其中就包括SDK的版本信息，用于成员SDK_INT表示；

对于VERSION_CODES在ＳＤＫ开发文档中时这样描述的，Enumeration of the currently known SDK version codes. These are the values that can be found in SDK. Version numbers increment monotonically with each official platform release.

在我们自己开发应用过程中，常常使用如下的代码形式判断运行新API还是旧的API:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)     {            // 包含新API的代码块    }    else    {            // 包含旧的API的代码块    }

以下为版本号:

 intBASEOctober 2008: The original, first, version of Android.intBASE_1_1February 2009: First Android update, officially called 1.1.intCUPCAKEMay 2009: Android 1.5.intCUR_DEVELOPMENTMagic version number for a current development build, which has not yet turned into an official release.intDONUTSeptember 2009: Android 1.6.intECLAIRNovember 2009: Android 2.0

Applications targeting this or a later release will get these new changes in behavior:

• The Service.onStartCommand function will return the newSTART_STICKY behavior instead of the old compatibilitySTART_STICKY_COMPATIBILITY.

intECLAIR_0_1December 2009: Android 2.0.1intECLAIR_MR1January 2010: Android 2.1intFROYOJune 2010: Android 2.2intGINGERBREADNovember 2010: Android 2.3

Applications targeting this or a later release will get these new changes in behavior:

• The application's notification icons will be shown on the new dark status bar background, so must be visible in this situation.

intGINGERBREAD_MR1February 2011: Android 2.3.3.intHONEYCOMBFebruary 2011: Android 3.0.intHONEYCOMB_MR1May 2011: Android 3.1.intHONEYCOMB_MR2June 2011: Android 3.2.intICE_CREAM_SANDWICHOctober 2011: Android 4.0.intICE_CREAM_SANDWICH_MR1December 2011: Android 4.0.3.intJELLY_BEANJune 2012: Android 4.1.intJELLY_BEAN_MR1Android 4.2: Moar jelly beans!

Applications targeting this or a later release will get these new changes in behavior:

• Content Providers: The default value of android:exported is now false.