When developing apps that support multiple API versions, you may want a standard way to provide newer features on earlier versions of Android or gracefully fall back to equivalent functionality. Rather than building code to handle earlier versions of the platform, you can leverage these libraries to provide that compatibility layer. In addition, the Support Libraries provide additional convenience classes and features not available in the standard Framework API for easier development and support across more devices.
Originally a single binary library for apps, the Android Support Library has evolved into a suite of libraries for app development. Many of these libraries are now a strongly recommended, if not essential, part of app development.
This document provides an overview of the support library to help you understand its components and how to use it effectively in your app.
Caution: Starting with Support Library release 24.2.0 (August 2016), the minimum supported API level across most support libraries has increased to Android 2.3 (API level 9) for most library packages. For more information, see Version Support and Package Names in this document.
Uses for the Support Libraries
There are a few distinct uses for the support libraries. Backward compatibility classes for earlier versions of the platform is just one of them. Here is a more complete list of ways you can use the support libraries in your app:
Backward Compatibility for newer APIs - A large amount of the
support libraries provide backward compatibility for newer framework
classes and methods. For example, the
Fragmentsupport class provides support for fragments on devices running versions earlier than Android 3.0 (API level 11).
Convenience and Helper Classes - The support libraries provides a
number of helper classes, particularly for user interface development. For
RecyclerViewclass provides an user interface widget for displaying and managing very long lists, useable on versions of Android from API level 7 and up.
- Debugging, Testing and Utilities - There are a number of classes that provide utility beyond code you incorporate into your app, including the support-annotations library for improved code lint checks on method inputs, the Testing Support Library, and the Multidex library for configuring and distributing apps with over 65,536 methods.
Using Support versus Framework APIs
Support Libraries provide classes and methods that closely resemble APIs in the Android Framework. Upon discovering this, you may wonder if you should use the framework version of the API or the support library equivalent. Here are the guidelines for when you should use support library classes in place of Framework APIs:
- Compatibility for a Specific Feature - If you want to support a recent platform feature on devices that a running earlier versions of the platform, use the equivalent classes and methods from the support library.
Compatibility for Related Library Features - More sophisticated
support library classes may depend on one or more additional support
library classes, so you should use support library classes for those
dependencies. For example, the
ViewPagersupport class should be used with
General Device Compatibility - If you do not have a specific
platform feature you intend to use with your app in a backward compatible
way, it is still a good idea to use support library classes in your app.
For example, you may want to use
ActivityCompatin place of the framework
Activityclass, so you can take advantage of newer features later on, such as incorporating the new permissions model introduced in Android 6.0 (API level 23).
Support Library classes that provide a compatible implementation of platform API classes may not be able to provide the full set of functionality available in the latest release, due to the limitations of the host device platform version. In these cases, Support Library classes are designed to degrade gracefully, and may not provide the all the functionality or data of the current, platform API. For this reason, you should review the reference documentation for the library classes and methods you use, and thoroughly test on devices running the earliest version of the platform supported by your app.
Note: The support libraries do not provide equivalent classes and methods for each framework API. In some cases, you may need to wrap a framework method call with an explicit SDK version check and provide alternative code to handle methods not available on a device. For more information on using version checks in your code, see Supporting Different Platform Versions.
Version Support and Package Names
Some of the Support Library packages have package names to indicate the minimum level of the API they support, using a v# notation, such as the support-v4 package. Starting with Support Library version 24.2.0 (released in August 2016), the minimum supported API level has changed to Android 2.3 (API level 9) for all support library packages. For this reason, when working with any recent release of the support library, you should not assume that the the v# package notation indicates a minimum API support level. This change in recent releases also means that library packages with the v4 and v7 are essentially equivalent in the minimum level of API they support. For example, the support-v4 and the support-v7 package both support a minimum API level of 9, for releases of the Support Library from 24.2.0 and higher.
For versions of the Support Library prior to release 24.2.0, the v# package notation does indicate a minimum version of the platform API supported by the library. In prior releases, the support-v4 package and the appcompat-v7 package support a minimum level of API level 4 and API level 7, respectively.
Support Library Release Versions
The release version of the Support Library, such as 24.2.0 or 25.0.1, is different from the minimum API level supported by any library in that release.The release version number indicates which version of the platform API it was built against, and therefore, what the most recent APIs may be included in this version of the libraries.
Specifically, the first section of the release version number, for example the 24 in version 24.2.0, generally corresponds with the version of the platform API available when it was released. The release version level of the support library indicates it incorporates some features of that API level, but you should not assume it provides compatibility with all features released in the new platform API version.
Most libraries in the Android Support Library suite have some dependency on
one or more libraries. For example, nearly all support libraries have a
dependency on the
support-compat package. In general, you do not
need to worry about support library dependencies, because the gradle build
tool manages library dependencies for you, by automatically including
If you want to see what libraries and library dependencies are included in your app, run the following command at the build root of your app development project to get a report of the dependencies for that project, including Android Support Libraries and other libraries:
gradle -q dependencies your-app-project:dependencies
Note that all Android Support Libraries also depend on some base level of the platform, for recent releases, that is Android 2.3 (API level 9) or higher.