Android中判断当前API的版本号

Android中由于不同版本API会有一些变化，导致一些较早版本可能不支持新的方法，或者某些功能处理过程不太一样，需要判断当前版本然后进行适当的处理。

那么，如何判断当前API的版本号呢？

例如判断api版本号是否大于等于19：

     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {...}  

其中， Build.VERSION_CODES. KITKAT  = 19

Build.VERSION.SDK_INT是什么：

public static final int SDK_INT = SystemProperties.getInt("ro.build.version.sdk", 0);

获取系统属性配置文件中“ro.build.version.sdk”的值，该值即为当前设备的系统版本号。

在Android源码 frameworks\base\core\java\android\os\Build.java 文件中的 Build.VERSION_CODES 类下包含对应各个版本的版本号信息。

以下是Android 7.0版本下的源码：

    public static class VERSION_CODES {
        /**
         * Magic version number for a current development build, which has
         * not yet turned into an official release.
         */
        public static final int CUR_DEVELOPMENT = 10000;
        
        /**
         * October 2008: The original, first, version of Android.  Yay!
         */
        public static final int BASE = 1;
        
        /**
         * February 2009: First Android update, officially called 1.1.
         */
        public static final int BASE_1_1 = 2;
        
        /**
         * May 2009: Android 1.5.
         */
        public static final int CUPCAKE = 3;
        
        /**
         * September 2009: Android 1.6.
         */
        public static final int DONUT = 4;
        
        /**
         * November 2009: Android 2.0
         */
        public static final int ECLAIR = 5;
        
        /**
         * December 2009: Android 2.0.1
         */
        public static final int ECLAIR_0_1 = 6;
        
        /**
         * January 2010: Android 2.1
         */
        public static final int ECLAIR_MR1 = 7;
        
        /**
         * June 2010: Android 2.2
         */
        public static final int FROYO = 8;
        
        /**
         * November 2010: Android 2.3
         */
        public static final int GINGERBREAD = 9;
        
        /**
         * February 2011: Android 2.3.3.
         */
        public static final int GINGERBREAD_MR1 = 10;

        /**
         * February 2011: Android 3.0.
         */
        public static final int HONEYCOMB = 11;
        
        /**
         * May 2011: Android 3.1.
         */
        public static final int HONEYCOMB_MR1 = 12;
        
        /**
         * June 2011: Android 3.2.
         */
        public static final int HONEYCOMB_MR2 = 13;

        /**
         * October 2011: Android 4.0.
         */
        public static final int ICE_CREAM_SANDWICH = 14;

        /**
         * December 2011: Android 4.0.3.
         */
        public static final int ICE_CREAM_SANDWICH_MR1 = 15;

        /**
         * June 2012: Android 4.1.
         */
        public static final int JELLY_BEAN = 16;

        /**
         * Android 4.2: Moar jelly beans!
         */
        public static final int JELLY_BEAN_MR1 = 17;

        /**
         * Android 4.3: Jelly Bean MR2, the revenge of the beans.
         */
        public static final int JELLY_BEAN_MR2 = 18;

        /**
         * Android 4.4: KitKat, another tasty treat.
         */
        public static final int KITKAT = 19;

        /**
         * Android 4.4W: KitKat for watches, snacks on the run.
         */ 
        public static final int KITKAT_WATCH = 20

        public static final int L = 21;

        /**
         * Lollipop. A flat one with beautiful shadows. But still tasty.  Android 5.0
         */   
        public static final int LOLLIPOP = 21;

        /**
         * Lollipop with an extra sugar coating on the outside!  Android 5.1 
         */  
        public static final int LOLLIPOP_MR1 = 22

        /**
         * M is for Marshmallow! Android 6.0
         */
        public static final int M = 23;

        /**
         * N is for ¯\_(ツ)_/¯. Android 7.0
         */
        public static final int N = 24;
    }