am fc279e51: Merge "Created Android University lesson for Multiple APKs." into ics-mr0

page.title=Creating Multiple APKs for Different API Levels

parent.title=Creating and Maintaining Multiple APKs

parent.link=index.html

trainingnavtop=true

next.title=Creating Multiple APKs for Different Screen Sizes

next.link=screensize.html

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<style type="text/css">

.blueCell { background-color: #9fc5e8;}

.greenCell { background-color: #b6d7a8;}

.redCell { background-color: #ea9999;}

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<div id="tb-wrapper">

<div id="tb">

<!-- table of contents -->

<h2>This lesson teaches you to</h2>

<ol>

  <li><a href="#Confirm">Confirm You Need Multiple APKs</a></li>

  <li><a href="#ChartReqs">Chart Your Requirements</a></li>

  <li><a href="#CreateLibrary">Put All Common Code and Resources in a Library Project</a></li>

  <li><a href="#CreateAPKs">Create New APK Projects</a></li>

  <li><a href="#AdjustManifests">Adjust the Manifests</a></li>

  <li><a href="#PreLaunch">Go Over Pre-launch Checklist</a></li>

</ol>

<!-- other docs (NOT javadocs) -->

<h2>You should also read</h2>

<ul>

  <li><a href="http://developer.android.com/guide/market/publishing/multiple-apks.html">Multiple APK

Support</a></li>

  <li><a

href="http://android-developers.blogspot.com/2010/07/how-to-have-your-cupcake-and-eat-it-too.html">

How to have your (Cup)cake and eat it too</a></li>

</ul>

</div>

</div>

<p>When developing your Android application to take advantage of multiple APKs on Android Market,

it’s important to adopt some good practices from the get-go, and prevent unnecessary headaches

further into the development process.  This lesson shows you how to create multiple APKs of your

app, each covering a slightly different range of API levels.  You will also gain some tools

necessary to make maintaining a multiple APK codebase as painless as possible.</p>

<h2 id="Confirm">Confirm You Need Multiple APKs</h2>

<p>When trying to create an application that works across multiple generations of the Android

platform, naturally you want your application to take advantage of new features on new devices,

without sacrificing backwards compatibility.  It may seem at the outset as though multiple APK

support is the best solution, but this often isn’t the case.  The <a

href="{@docRoot}guide/market/publishing/multiple-apks.html#ApiLevelOptions">Using Single APK

Instead</a> section of the multiple APK developer guide includes some useful information on how to

accomplish this with a single APK, including use of our support library. You can also learn how to

write code that runs only at certain API levels in a single APK, without resorting to

computationally expensive techniques like reflection from  <a

href="http://android-developers.blogspot.com/2010/07/how-to-have-your-cupcake-and-eat-it-too.html">

this article</a>.</p>

<p>If you can manage it, confining your application to a single APK has several

advantages, including:</p>

<ul>

<li>Publishing and testing are easier</li>

<li>There’s only one codebase to maintain</li>

<li>Your application can adapt to device configuration changes</li>

<li>App restore across devices just works</li>

<li>You don’t have to worry about market preference, behavior from "upgrades" from one APK to the

next, or which APK goes with which class of devices

</ul>

<p>The rest of this lesson assumes that you’ve researched the topic, studiously absorbed the

material in the resources linked, and determined that multiple APKs are the right path for your

application.</p>

<h2 id="ChartReqs">Chart Your Requirements</h2>

<p>Start off by creating a simple chart to quickly determine how many APKs you need, and what API

range each APK covers.  For handy reference, the <a

href="{@docRoot}resources/dashboard/platform-versions.html">Platform Versions</a> page of the

Android Developer website provides data about the relative number of active devices running a given

version of the Android platform.  Also, although it sounds easy at first, keeping track of which set

of API levels each APK is going to target gets difficult rather quickly, especially if there’s going

to be some overlap (there often is).  Fortunately, it’s easy to chart out your requirements quickly,

easily, and have an easy reference for later.</p>

<p>In order to create your multiple APK chart, start out with a row of cells representing the

various API levels of the Android platform.  Throw an extra cell at the end to represent future

versions of Android.</p>

<table cellpadding="10" cellspacing="0" border="1">

  <tbody>

    <tr>

      <td>3</td>

      <td>4</td>

      <td>5</td>

      <td>6</td>

      <td>7</td>

      <td>8</td>

      <td>9</td>

      <td>10</td>

      <td>11</td>

      <td>12</td>

      <td>13</td>

      <td>+</td>

    </tr>

  </tbody>

</table>

<p>Now just color in the chart such that each color represents an APK.  Here’s one example of how

you might apply each APK to a certain range of API levels.</p>

<table cellpadding="10" cellspacing="0" border="1">

  <tbody>

    <tr>

      <td class="blueCell">3</td>

      <td class="blueCell">4</td>

      <td class="blueCell">5</td>

      <td class="blueCell">6</td>

      <td class="greenCell">7</td>

      <td class="greenCell">8</td>

      <td class="greenCell">9</td>

      <td class="greenCell">10</td>

      <td class="redCell">11</td>

      <td class="redCell">12</td>

      <td class="redCell">13</td>

      <td class="redCell">+</td>

    </tr>

  </tbody>

</table>

<p>Once you’ve created this chart, distribute it to your team.  Team communication on your project

just got immediately simpler, since instead of asking "How’s the APK for API levels 3 to 6, er, you

know, the Android 1.x one.  How’s that coming along?"  You can simply say "How’s the Blue APK coming

along?"</p>

<h2 id="CreateLibrary">Put All Common Code and Resources in a Library Project</h2>

<p>Whether you’re modifying an existing Android application or starting one from scratch, this is

the first thing that you should do to the codebase, and by the far the most important.  Everything

that goes into the library project only needs to be updated once (think language-localized strings,

color themes, bugs fixed in shared code), which improves your development time and reduces the

likelihood of mistakes that could have been easily avoided.</p>

<p class="note"><strong>Note:</strong>  While the implementation details of how to create and

include library projects are beyond the scope of this lesson, you can get up to speed quickly on

their creation at the following links:</p>

<ul>

<li><a

href="{@docRoot}guide/developing/projects/projects-eclipse.html#SettingUpLibraryProject">Setting up

a library project (Eclipse)</a></li>

<li><a

href="{@docRoot}guide/developing/projects/projects-cmdline.html#SettingUpLibraryProject">Setting up

a library project (Command line)</a></li>

</ul>

<p>If you’re converting an existing application to use multiple APK support,

scour your codebase for every localized string file, list of values, theme

colors, menu icons and layout that isn’t going to change across APKs, and put

it all in the library project.  Code that isn’t going to change much should

also go in the library project.  You’ll likely find yourself extending these

classes to add a method or two from APK to APK.</p>

<p>If, on the other hand, you’re creating the application from scratch, try as

much as possible to write code in the library project <em>first</em>, then only move it down to an

individual APK if necessary.  This is much easier to manage in the long run than adding it to one,

then another, then another, then months later trying to figure out whether this blob can be moved up

to the library section without screwing anything up.</p>

<h2 id="CreateAPKs">Create New APK Projects</h2>

<p>There should be a separate Android project for each APK you’re going to release.  For easy

organization, place the library project and all related APK projects under the same parent folder. 

Also remember that each APK needs to have the same package name, although they don’t necessarily

need to share the package name with the library.  If you were to have 3 APKs following the scheme

described earlier, your root directory might look like this:</p>

<pre class="no-pretty-print classic">

alexlucas:~/code/multi-apks-root$ ls

foo-blue

foo-green

foo-lib

foo-red

</pre>

<p>Once the projects are created, add the library project as a reference to each APK project.  If

possible, define your starting Activity in the library project, and extend that Activity in your APK

project.  Having a starting activity defined in the library project gives you a chance to put all

your application initialization in one place, so that each individual APK doesn’t have to

re-implement "universal" tasks like initializing Analytics, running licensing checks, and any other

initialization procedures that don’t change much from APK to APK.</p>

<h2 id="AdjustManifests">Adjust the Manifests</h2>

<p>When a user downloads an application which uses multiple APKs through Android Market, the correct

APK to use is chosen using two simple rules:</p>

<ul>

<li>The manifest has to show that particular APK is eligible</li>

<li>Of the eligible APKs, highest version number wins</li>

</ul>

<p>

By way of example, let’s take the set of multiple APKs described earlier, and assume that we haven’t

set a max API level for any of the APKs.  Taken individually, the possible range of each APK would

look like this:</p>

<table cellpadding="10" cellspacing="0" border="1">

  <tbody>

    <tr>

      <td class="blueCell">3</td>

      <td class="blueCell">4</td>

      <td class="blueCell">5</td>

      <td class="blueCell">6</td>

      <td class="blueCell">7</td>

      <td class="blueCell">8</td>

      <td class="blueCell">9</td>

      <td class="blueCell">10</td>

      <td class="blueCell">11</td>

      <td class="blueCell">12</td>

      <td class="blueCell">13</td>

      <td class="blueCell">+</td>

    </tr>

    <tr>

      <td class="blackCell">3</td>

      <td class="blackCell">4</td>

      <td class="blackCell">5</td>

      <td class="blackCell">6</td>

      <td class="greenCell">7</td>

      <td class="greenCell">8</td>

      <td class="greenCell">9</td>

      <td class="greenCell">10</td>

      <td class="greenCell">11</td>

      <td class="greenCell">12</td>

      <td class="greenCell">13</td>

      <td class="greenCell">+</td>

    </tr>

    <tr>

      <td class="blackCell">3</td>

      <td class="blackCell">4</td>

      <td class="blackCell">5</td>

      <td class="blackCell">6</td>

      <td class="blackCell">7</td>

      <td class="blackCell">8</td>

      <td class="blackCell">9</td>

      <td class="blackCell">10</td>

      <td class="redCell">11</td>

      <td class="redCell">12</td>

      <td class="redCell">13</td>

      <td class="redCell">+</td>

    </tr>

  </tbody>

</table>

<p>

Because it is required that an APK with a higher minSdkVersion also have a

higher version code, we know that in terms of versionCode values, red ≥

green &#8805; blue.  Therefore we can effectively collapse the chart to look like this:</p>

<table cellpadding="10" cellspacing="0" border="1">

  <tbody>

    <tr>

      <td class="blueCell">3</td>

      <td class="blueCell">4</td>

      <td class="blueCell">5</td>

      <td class="blueCell">6</td>

      <td class="greenCell">7</td>

      <td class="greenCell">8</td>

      <td class="greenCell">9</td>

      <td class="greenCell">10</td>

      <td class="redCell">11</td>

      <td class="redCell">12</td>

      <td class="redCell">13</td>

      <td class="redCell">+</td>

    </tr>

  </tbody>

</table>

<p>

Now, let’s further assume that the Red APK has some requirement on it that the other two don’t.  The

Market Filters page of the Android Developer guide has a whole list of possible culprits.  For the

sake of example, let’s assume that red requires a front-facing camera.  In fact, the entire point of

the red APK is to combine the front-facing camera with sweet new functionality that was added in API

11.  But, it turns out, not all devices that support API 11 even HAVE front-facing cameras!  The

horror!</p>

<p>Fortunately, if a user is browsing Market from one such device, Android Market will look at the

manifest, see that Red lists the front-facing camera as a requirement, and quietly ignore it, having

determined that Red and that device are not a match made in digital heaven.  It will then see that

Green is not only forward-compatible with devices with API 11 (since no maxSdkVersion was defined),

but also doesn’t care whether or not there’s a front-facing camera!  The app can still be downloaded

from Android Market by the user, because despite the whole front-camera mishap, there was still an

APK that supported that particular API level.</p>

<p>  In order to keep all your APKs on separate "tracks", it’s important to have a good version code

scheme.  The recommended one can be found on the <a

href="{@docRoot}guide/market/publishing/multiple-apks.html#VersionCodes">Version Codes</a> area of

our developer guide.  Since the example set of APKs is only dealing with one of 3 possible

dimensions, it would be sufficient to separate each APK by 1000, set the first couple digits to the

minSdkVersion for that particular APK, and increment from there.  This might look like:</p>

<p>Blue: 03001, 03002, 03003, 03004...<br />

Green: 07001, 07002, 07003, 07004...<br />

Red:11001, 11002, 11003, 11004...</p>

<p>  Putting this all together, your Android Manifests would likely look something like the following:</p>

<p>Blue:</p>

<pre>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    android:versionCode="03001" android:versionName="1.0" package="com.example.foo">

    <uses-sdk android:minSdkVersion="3" />

    ...

</pre>

<p>Green:</p>

<pre>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    android:versionCode="07001" android:versionName="1.0" package="com.example.foo">

    <uses-sdk android:minSdkVersion="7" />

    ...

</pre>

<p>Red:</p>

<pre>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    android:versionCode="11001" android:versionName="1.0" package="com.example.foo">

    <uses-sdk android:minSdkVersion="11" />

    ...

</pre>

<h2 id="PreLaunch">Go Over Pre-launch Checklist</h2>

<p>  Before uploading to Android Market, double-check the following items.  Remember that these are specifically relevant to multiple APKs, and in no way represent a complete checklist for all applications being uploaded to Android Market.</p>

<ul>

<li>All APKs must have the same package name</li>

<li>All APKs must be signed with the same certificate</li>

<li>If the APKs overlap in platform version, the one with the higher minSdkVersion must have a higher version code</li>

<li>Double check your manifest filters for conflicting information (an APK that only supports cupcake on XLARGE screens isn’t going to be seen by anybody)</li>

<li>Each APK's manifest must be unique across at least one of supported screen, openGL texture, or platform version</li>

<li>Try to test each APK on at least one device.  Barring that, you have one of the most customizable device emulators in the business sitting on your development machine.  Go nuts!</li>

</ul>

<p>It’s also worth inspecting the compiled APK before pushing to market, to make sure there aren’t

any surprises that could hide your application in Market.  This is actually quite simple using the

"aapt" tool.  Aapt (the Android Asset Packaging Tool) is part of the build process for creating and

packaging your Android applications, and is also a very handy tool for inspecting them. </p>

<pre class="no-pretty-print classic">

>aapt dump badging

package: name='com.example.hello' versionCode='1' versionName='1.0'

sdkVersion:'11'

uses-permission:'android.permission.SEND_SMS'

application-label:'Hello'

application-icon-120:'res/drawable-ldpi/icon.png'

application-icon-160:'res/drawable-mdpi/icon.png'

application-icon-240:'res/drawable-hdpi/icon.png'

application: label='Hello' icon='res/drawable-mdpi/icon.png'

launchable-activity: name='com.example.hello.HelloActivity'  label='Hello' icon=''

uses-feature:'android.hardware.telephony'

uses-feature:'android.hardware.touchscreen'

main

supports-screens: 'small' 'normal' 'large' 'xlarge'

supports-any-density: 'true'

locales: '--_--'

densities: '120' '160' '240'

</pre>

<p>When you examine aapt output, be sure to check that you don’t have conflicting values for

supports-screens and compatible-screens, and that you don’t have unintended "uses-feature" values

that were added as a result of permissions you set in the manifest. In the example above, the APK

won’t be visible to very many devices.</p>

<p>Why?  By adding the required permission SEND_SMS, the feature requirement of android.hardware.telephony was implicitly added.  Since API 11 is Honeycomb (the version of Android optimized specifically for tablets), and no Honeycomb devices have telephony hardware in them, Market will filter out this APK in all cases, until future devices come along which are higher in API level AND possess telephony hardware.

</p>

<p>Fortunately this is easily fixed by adding the following to your manifest:</p>

<pre>

<uses-feature android:name="android.hardware.telephony" android:required="false" />

</pre>

<p>Once you’ve completed the pre-launch checklist, upload your APKs to Android Market.  It may take a bit for the application to show up when browsing Android Market, but when it does, perform one last check.  Download the application onto any test devices you may have, to make sure that the APKs are targeting the intended devices.  Congratulations, you’re done!</p>

page.title=Creating and Maintaining Multiple APKs

trainingnavtop=true

startpage=true

next.title=Creating Multiple APKs for Different API Levels

next.link=api.html

@jd:body

<div id="tb-wrapper">

<div id="tb">

<!-- Required platform, tools, add-ons, devices, knowledge, etc. -->

<h2>Dependencies and prerequisites</h2>

<ul>

  <li>Android 1.0 and higher</li>

  <li>You must have an <a href="http://market.android.com/publish">Android Market</a> publisher

account</li>

</ul>

<!-- related docs (NOT javadocs) -->

<h2>You should also read</h2>

<ul>

  <li><a href="http://developer.android.com/guide/market/publishing/multiple-apks.html">Multiple APK

Support</a></li>

</ul>

</div>

</div>

<p>Multiple APK support is a feature in Android Market that allows you to publish multiple APKs

under the same application listing.  Each APK is a complete instance of your application, optimized

to target specific device configurations.  Each APK can target a specific set of GL

textures, API levels, screen sizes, or some combination thereof.</p>

<p>This class shows you how to write your multiple APK application using any one of these

configuration variables.  Each lesson covers basics about how to organize your codebase and target

the right devices, as well as the smart way to avoid pitfalls such as unnecessary redundancy across

your codebase, and making mistakes in your manifest that could render an APK invisible to all

devices in Android Market.  By going through any of these lessons, you'll know how to develop

multiple APKs the smart way, make sure they're targeting the devices you want them to,

and know how to catch mistakes <em>before</em> your app goes live.</p>

<h2>Lessons</h2>

<dl>

  <dt><b><a href="api.html">Creating Multiple APKs for Different API Levels</a></b></dt>

    <dd>Learn how to target different versions of the Android platform using multiple APKs.  Also

learn how to organize your codebase, what to do with your manifest, and how to investigate your APK

configuration using the <code>aapt</code> tool before pushing live.</dd>

  <dt><b><a href="screensize.html">Creating Multiple APKs for Different Screen Sizes</a></b></dt>

    <dd>Learn how to target Android devices by screen size using multiple APKs.  Also learn how to

organize your codebase, what to do with your manifest, and how to investigate your APK configuration

using the <code>aapt</code> tool before pushing live.</dd>

  <dt><b><a href="texture.html">Creating Multiple APKs for Different GL Textures</a></b></dt>

        <dd>Learn how to target Android devices based on their support for GL texture.  Also learn

how to organize your codebase, what to do with your manifest, and how to investigate your APK

configuration using the <code>aapt</code> tool before pushing live.</dd>

  <dt><b><a href="multiple.html">Creating Multiple APKs with 2+ Dimensions</a></b></dt>

        <dd>Learn how to target different Android devices based on more than one configuration

variable (screen size, API version, GL texture).  Examples in the lesson target using a combination

of API level and screen size.  Also learn how to organize your codebase, what to do with your

manifest, and how to investigate your APK configuration using the <code>aapt</code> tool before

pushing live.</dd>

</dl>