Android中使用Build获取当前系统SDK版本

android中部分API的使用，需要在特定的SDK版本之后才能使用，因此在兼容老版本SDK的时候，经常需要判断API的版本。

Android中提供了Build类来判断API的版本，我们可以这样子操作：

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR1) {
       // TODO
} 

Build.VERSION.SDK_INT来获取当前API的版本

/**
* The user-visible SDK version of the framework; its possible
* values are defined in {@link Build.VERSION_CODES}.
*/
public static final int SDK_INT = SystemProperties.getInt( "ro.build.version.sdk", 0);

而Build.VERSION_CODES中存储了我们所有API的版本：

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

         * 
 They must explicitly request the
         * {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE} permission to be
         * able to modify the contents of the SD card.  (Apps targeting
         * earlier versions will always request the permission.)
         * 
 They must explicitly request the
         * {@link android.Manifest.permission#READ_PHONE_STATE} permission to be
         * able to be able to retrieve phone state info.  (Apps targeting
         * earlier versions will always request the permission.)
         * 
 They are assumed to support different screen densities and
         * sizes.  (Apps targeting earlier versions are assumed to only support
         * medium density normal size screens unless otherwise indicated).
         * They can still explicitly specify screen support either way with the
         * supports-screens manifest tag.
         * 
 {@link android.widget.TabHost} will use the new dark tab
         * background design.
         * 
         */
        public static final int DONUT = 4;
        
        /**
         * November 2009: Android 2.0
         * 
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 The {@link android.app.Service#onStartCommand
         * Service.onStartCommand} function will return the new
         * {@link android.app.Service#START_STICKY} behavior instead of the
         * old compatibility {@link android.app.Service#START_STICKY_COMPATIBILITY}.
         * 
 The {@link android.app.Activity} class will now execute back
         * key presses on the key up instead of key down, to be able to detect
         * canceled presses from virtual keys.
         * 
 The {@link android.widget.TabWidget} class will use a new color scheme
         * for tabs. In the new scheme, the foreground tab has a medium gray background
         * the background tabs have a dark gray background.
         * 
         */
        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
         *
         * 
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.
         * 
         */
        public static final int GINGERBREAD = 9;
        
        /**
         * February 2011: Android 2.3.3.
         */
        public static final int GINGERBREAD_MR1 = 10;

        /**
         * February 2011: Android 3.0.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 The default theme for applications is now dark holographic:
         *      {@link android.R.style#Theme_Holo}.
         * 
 On large screen devices that do not have a physical menu
         * button, the soft (compatibility) menu is disabled.
         * 
 The activity lifecycle has changed slightly as per
         * {@link android.app.Activity}.
         * 
 An application will crash if it does not call through
         * to the super implementation of its
         * {@link android.app.Activity#onPause Activity.onPause()} method.
         * 
 When an application requires a permission to access one of
         * its components (activity, receiver, service, provider), this
         * permission is no longer enforced when the application wants to
         * access its own component.  This means it can require a permission
         * on a component that it does not itself hold and still access that
         * component.
         * 
 {@link android.content.Context#getSharedPreferences
         * Context.getSharedPreferences()} will not automatically reload
         * the preferences if they have changed on storage, unless
         * {@link android.content.Context#MODE_MULTI_PROCESS} is used.
         * 
 {@link android.view.ViewGroup#setMotionEventSplittingEnabled}
         * will default to true.
         * 
 {@link android.view.WindowManager.LayoutParams#FLAG_SPLIT_TOUCH}
         * is enabled by default on windows.
         * 
 {@link android.widget.PopupWindow#isSplitTouchEnabled()
         * PopupWindow.isSplitTouchEnabled()} will return true by default.
         * 
 {@link android.widget.GridView} and {@link android.widget.ListView}
         * will use {@link android.view.View#setActivated View.setActivated}
         * for selected items if they do not implement {@link android.widget.Checkable}.
         * 
 {@link android.widget.Scroller} will be constructed with
         * "flywheel" behavior enabled by default.
         * 
         */
        public static final int HONEYCOMB = 11;
        
        /**
         * May 2011: Android 3.1.
         */
        public static final int HONEYCOMB_MR1 = 12;
        
        /**
         * June 2011: Android 3.2.
         *
         * 
Update to Honeycomb MR1 to support 7 inch tablets, improve
         * screen compatibility mode, etc.
         *
         * 
As of this version, applications that don't say whether they
         * support XLARGE screens will be assumed to do so only if they target
         * {@link #HONEYCOMB} or later; it had been {@link #GINGERBREAD} or
         * later.  Applications that don't support a screen size at least as
         * large as the current screen will provide the user with a UI to
         * switch them in to screen size compatibility mode.
         *
         * 
This version introduces new screen size resource qualifiers
         * based on the screen size in dp: see
         * {@link android.content.res.Configuration#screenWidthDp},
         * {@link android.content.res.Configuration#screenHeightDp}, and
         * {@link android.content.res.Configuration#smallestScreenWidthDp}.
         * Supplying these in  as per
         * {@link android.content.pm.ApplicationInfo#requiresSmallestWidthDp},
         * {@link android.content.pm.ApplicationInfo#compatibleWidthLimitDp}, and
         * {@link android.content.pm.ApplicationInfo#largestWidthLimitDp} is
         * preferred over the older screen size buckets and for older devices
         * the appropriate buckets will be inferred from them.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
New {@link android.content.pm.PackageManager#FEATURE_SCREEN_PORTRAIT}
         * and {@link android.content.pm.PackageManager#FEATURE_SCREEN_LANDSCAPE}
         * features were introduced in this release.  Applications that target
         * previous platform versions are assumed to require both portrait and
         * landscape support in the device; when targeting Honeycomb MR1 or
         * greater the application is responsible for specifying any specific
         * orientation it requires.
         * 
{@link android.os.AsyncTask} will use the serial executor
         * by default when calling {@link android.os.AsyncTask#execute}.
         * 
{@link android.content.pm.ActivityInfo#configChanges
         * ActivityInfo.configChanges} will have the
         * {@link android.content.pm.ActivityInfo#CONFIG_SCREEN_SIZE} and
         * {@link android.content.pm.ActivityInfo#CONFIG_SMALLEST_SCREEN_SIZE}
         * bits set; these need to be cleared for older applications because
         * some developers have done absolute comparisons against this value
         * instead of correctly masking the bits they are interested in.
         * 
         */
        public static final int HONEYCOMB_MR2 = 13;

        /**
         * October 2011: Android 4.0.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 For devices without a dedicated menu key, the software compatibility
         * menu key will not be shown even on phones.  By targeting Ice Cream Sandwich
         * or later, your UI must always have its own menu UI affordance if needed,
         * on both tablets and phones.  The ActionBar will take care of this for you.
         * 
 2d drawing hardware acceleration is now turned on by default.
         * You can use
         * {@link android.R.attr#hardwareAccelerated android:hardwareAccelerated}
         * to turn it off if needed, although this is strongly discouraged since
         * it will result in poor performance on larger screen devices.
         * 
 The default theme for applications is now the "device default" theme:
         *      {@link android.R.style#Theme_DeviceDefault}. This may be the
         *      holo dark theme or a different dark theme defined by the specific device.
         *      The {@link android.R.style#Theme_Holo} family must not be modified
         *      for a device to be considered compatible. Applications that explicitly
         *      request a theme from the Holo family will be guaranteed that these themes
         *      will not change character within the same platform version. Applications
         *      that wish to blend in with the device should use a theme from the
         *      {@link android.R.style#Theme_DeviceDefault} family.
         * 
 Managed cursors can now throw an exception if you directly close
         * the cursor yourself without stopping the management of it; previously failures
         * would be silently ignored.
         * 
 The fadingEdge attribute on views will be ignored (fading edges is no
         * longer a standard part of the UI).  A new requiresFadingEdge attribute allows
         * applications to still force fading edges on for special cases.
         * 
 {@link android.content.Context#bindService Context.bindService()}
         * will not automatically add in {@link android.content.Context#BIND_WAIVE_PRIORITY}.
         * 
 App Widgets will have standard padding automatically added around
         * them, rather than relying on the padding being baked into the widget itself.
         * 
 An exception will be thrown if you try to change the type of a
         * window after it has been added to the window manager.  Previously this
         * would result in random incorrect behavior.
         * 
 {@link android.view.animation.AnimationSet} will parse out
         * the duration, fillBefore, fillAfter, repeatMode, and startOffset
         * XML attributes that are defined.
         * 
 {@link android.app.ActionBar#setHomeButtonEnabled
         * ActionBar.setHomeButtonEnabled()} is false by default.
         * 
         */
        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.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 You must explicitly request the {@link android.Manifest.permission#READ_CALL_LOG}
         * and/or {@link android.Manifest.permission#WRITE_CALL_LOG} permissions;
         * access to the call log is no longer implicitly provided through
         * {@link android.Manifest.permission#READ_CONTACTS} and
         * {@link android.Manifest.permission#WRITE_CONTACTS}.
         * 
 {@link android.widget.RemoteViews} will throw an exception if
         * setting an onClick handler for views being generated by a
         * {@link android.widget.RemoteViewsService} for a collection container;
         * previously this just resulted in a warning log message.
         * 
 New {@link android.app.ActionBar} policy for embedded tabs:
         * embedded tabs are now always stacked in the action bar when in portrait
         * mode, regardless of the size of the screen.
         * 
 {@link android.webkit.WebSettings#setAllowFileAccessFromFileURLs(boolean)
         * WebSettings.setAllowFileAccessFromFileURLs} and
         * {@link android.webkit.WebSettings#setAllowUniversalAccessFromFileURLs(boolean)
         * WebSettings.setAllowUniversalAccessFromFileURLs} default to false.
         * 
 Calls to {@link android.content.pm.PackageManager#setComponentEnabledSetting
         * PackageManager.setComponentEnabledSetting} will now throw an
         * IllegalArgumentException if the given component class name does not
         * exist in the application's manifest.
         * 
 {@link android.nfc.NfcAdapter#setNdefPushMessage
         * NfcAdapter.setNdefPushMessage},
         * {@link android.nfc.NfcAdapter#setNdefPushMessageCallback
         * NfcAdapter.setNdefPushMessageCallback} and
         * {@link android.nfc.NfcAdapter#setOnNdefPushCompleteCallback
         * NfcAdapter.setOnNdefPushCompleteCallback} will throw
         * IllegalStateException if called after the Activity has been destroyed.
         * 
 Accessibility services must require the new
         * {@link android.Manifest.permission#BIND_ACCESSIBILITY_SERVICE} permission or
         * they will not be available for use.
         * 
 {@link android.accessibilityservice.AccessibilityServiceInfo#FLAG_INCLUDE_NOT_IMPORTANT_VIEWS
         * AccessibilityServiceInfo.FLAG_INCLUDE_NOT_IMPORTANT_VIEWS} must be set
         * for unimportant views to be included in queries.
         * 
         */
        public static final int JELLY_BEAN = 16;

        /**
         * November 2012: Android 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 {@code android:exported} is now
         * {@code false}. See
         * 
         * the android:exported section in the provider documentation for more details.
         * 
{@link android.view.View#getLayoutDirection() View.getLayoutDirection()}
         * can return different values than {@link android.view.View#LAYOUT_DIRECTION_LTR}
         * based on the locale etc.
         * 
 {@link android.webkit.WebView#addJavascriptInterface(Object, String)
         * WebView.addJavascriptInterface} requires explicit annotations on methods
         * for them to be accessible from Javascript.
         * 
         */
        public static final int JELLY_BEAN_MR1 = 17;

        /**
         * July 2013: Android 4.3, the revenge of the beans.
         */
        public static final int JELLY_BEAN_MR2 = 18;

        /**
         * October 2013: Android 4.4, KitKat, another tasty treat.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 The default result of {android.preference.PreferenceActivity#isValidFragment
         * PreferenceActivity.isValueFragment} becomes false instead of true.
         * 
 In {@link android.webkit.WebView}, apps targeting earlier versions will have
         * JS URLs evaluated directly and any result of the evaluation will not replace
         * the current page content.  Apps targetting KITKAT or later that load a JS URL will
         * have the result of that URL replace the content of the current page
         * 
 {@link android.app.AlarmManager#set AlarmManager.set} becomes interpreted as
         * an inexact value, to give the system more flexibility in scheduling alarms.
         * 
 {@link android.content.Context#getSharedPreferences(String, int)
         * Context.getSharedPreferences} no longer allows a null name.
         * 
 {@link android.widget.RelativeLayout} changes to compute wrapped content
         * margins correctly.
         * 
 {@link android.app.ActionBar}'s window content overlay is allowed to be
         * drawn.
         * 
The {@link android.Manifest.permission#READ_EXTERNAL_STORAGE}
         * permission is now always enforced.
         * 
Access to package-specific external storage directories belonging
         * to the calling app no longer requires the
         * {@link android.Manifest.permission#READ_EXTERNAL_STORAGE} or
         * {@link android.Manifest.permission#WRITE_EXTERNAL_STORAGE}
         * permissions.
         * 
         */
        public static final int KITKAT = 19;

        /**
         * Android 4.4W: KitKat for watches, snacks on the run.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
{@link android.app.AlertDialog} might not have a default background if the theme does
         * not specify one.
         * 
         */
        public static final int KITKAT_WATCH = 20;

        /**
         * Temporary until we completely switch to {@link #LOLLIPOP}.
         * @hide
         */
        public static final int L = 21;

        /**
         * Lollipop.  A flat one with beautiful shadows.  But still tasty.
         *
         * 
Applications targeting this or a later release will get these
         * new changes in behavior:
         * 

         * 
 {@link android.content.Context#bindService Context.bindService} now
         * requires an explicit Intent, and will throw an exception if given an implicit
         * Intent.
         * 
 {@link android.app.Notification.Builder Notification.Builder} will
         * not have the colors of their various notification elements adjusted to better
         * match the new material design look.
         * 
 {@link android.os.Message} will validate that a message is not currently
         * in use when it is recycled.
         * 
 Hardware accelerated drawing in windows will be enabled automatically
         * in most places.
         * 
 {@link android.widget.Spinner} throws an exception if attaching an
         * adapter with more than one item type.
         * 
 If the app is a launcher, the launcher will be available to the user
         * even when they are using corporate profiles (which requires that the app
         * use {@link android.content.pm.LauncherApps} to correctly populate its
         * apps UI).
         * 
 Calling {@link android.app.Service#stopForeground Service.stopForeground}
         * with removeNotification false will modify the still posted notification so that
         * it is no longer forced to be ongoing.
         * 
 A {@link android.service.dreams.DreamService} must require the
         * {@link android.Manifest.permission#BIND_DREAM_SERVICE} permission to be usable.
         * 
         */
        public static final int LOLLIPOP = 21;

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