1page.title=Compatibility Program Overview 2@jd:body 3 4<!-- 5 Copyright 2015 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18--> 19<div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"> 23 </ol> 24 </div> 25</div> 26 27<p>The Android compatibility program makes it easy for mobile device 28manufacturers to develop compatible Android devices.</p> 29<h2 id="program-goals">Program goals</h2> 30<p>The Android compatibility program works for the benefit of the entire 31Android community, including users, developers, and device manufacturers.</p> 32<p>Each group depends on the others. Users want a wide selection of devices 33and great apps; great apps come from developers motivated by a large market 34for their apps with many devices in users' hands; device manufacturers rely 35on a wide variety of great apps to increase their products' value for 36consumers.</p> 37<p>Our goals were designed to benefit each of these groups:</p> 38<ul> 39<li> 40<p><em>Provide a consistent application and hardware environment to application 41developers.</em> 42 Without a strong compatibility standard, devices can vary so 43greatly that developers must design different versions of their applications 44for different devices. The compatibility program provides a precise definition 45of what developers can expect from a compatible device in terms of APIs and 46capabilities. Developers can use this information to make good design 47decisions, and be confident that their apps will run well on any compatible 48device.</p> 49</li> 50<li> 51<p><em>Enable a consistent application experience for consumers.</em> 52 If an application runs well on one compatible Android device, it should run well on 53any other device that is compatible with the same Android platform version. 54Android devices will differ in hardware and software capabilities, so the 55compatibility program also provides the tools needed for distribution systems 56such as Google Play to implement appropriate filtering. This means 57users see only the applications they can actually run.</p> 58</li> 59<li> 60<p><em>Enable device manufacturers to differentiate while being 61compatible.</em> 62 The Android compatibility program focuses on the aspects of 63Android relevant to running third-party applications, which allows device 64manufacturers the flexibility to create unique devices that are nonetheless 65compatible.</p> 66</li> 67<li> 68<p><em>Minimize costs and overhead associated with compatibility.</em> 69 Ensuring compatibility should be easy and inexpensive to 70device manufacturers. The testing tool is free, open source, and 71available for <a href="downloads.html">download</a>. 72It is designed to be used for continuous self-testing 73during the device development process to eliminate the cost of changing your 74workflow or sending your device to a third party for testing. Meanwhile, there 75are no required certifications, and thus no corresponding costs and 76fees.</p> 77</li> 78</ul> 79<p>The Android compatibility program consists of three key components:</p> 80<ul> 81<li>The source code to the Android software stack</li> 82<li>The Compatilbility Definition Document (CDD), representing the "policy" aspect of compatibility</li> 83<li>The Compatilbility Test Suite (CTS), representing the "mechanism" of compatibility</li> 84</ul> 85<p>Just as each version of the Android platform exists in a separate branch in 86the source code tree, there is a separate CTS and CDD for each version as 87well. The CDD, CTS, and source code are -- along with your hardware and your 88software customizations -- everything you need to create a compatible device.</p> 89<h2 id="compatibility-definition-document-cdd">Compatibility Definition Document</h2> 90<p>For each release of the Android platform, a detailed CDD will be provided. The CDD represents the "policy" 91aspect of Android compatibility.</p> 92<p>No test suite, including CTS, can truly be comprehensive. For instance, the 93CTS includes a test that checks for the presence and correct behavior of 94OpenGL graphics APIs, but no software test can verify that the graphics 95actually appear correctly on the screen. More generally, it's impossible to 96test the presence of hardware features such as keyboards, display density, 97Wi-Fi, and Bluetooth.</p> 98<p>The CDD's role is to codify and clarify specific requirements, and 99eliminate ambiguity. The CDD does not attempt to be comprehensive. Since 100Android is a single corpus of open-source code, the code itself is the 101comprehensive "specification" of the platform and its APIs. The CDD acts as a 102"hub" referencing other content (such as SDK API documentation) that provides 103a framework in which the Android source code may be used so that the end 104result is a compatible system.</p> 105<p>If you want to build a device compatible with a given Android version, 106start by checking out the source code for that version, and then read the 107corresponding CDD and stay within its guidelines. For additional details, 108simply examine <a href="/compatibility/android-cdd.pdf">the latest CDD</a>.</p> 109<h2 id="compatibility-test-suite-cts">Compatibility Test Suite</h2> 110<p>The <a href="cts/index.html">CTS</a> is a free, commercial-grade test suite, 111available for <a href="downloads.html">download</a>. 112The CTS represents the "mechanism" of compatibility.</p> 113<p>The CTS runs on a desktop machine and executes test cases directly on 114attached devices or an emulator. The CTS is a set of unit tests designed to be 115integrated into the daily workflow (such as via a continuous build system) of 116the engineers building a device. Its intent is to reveal incompatibilities 117early on, and ensure that the software remains compatible throughout the 118development process.</p> 119<h2 id="compatibility-test-suite-verifier-cts-verifier">Compatibility Test Suite Verifier (CTS Verifier)</h2> 120<p>The Compatibility Test Suite Verifier (CTS Verifier) is a supplement to the 121CTS available for <a href="downloads.html">download</a>. 122CTS Verifier provides tests for APIs and functions that cannot be tested on a 123stationary device without manual input (e.g. audio quality, accelerometer, etc).</p> 124<p>For details on the CTS, consult the <a href="cts/index.html">CTS introduction</a>.</p> 125 126 127