148 lines
7.8 KiB
Plaintext
148 lines
7.8 KiB
Plaintext
page.title=Strategies for Android 1.5
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parent.title=Supporting Multiple Screens
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parent.link=screens_support.html
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@jd:body
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<div id="qv-wrapper">
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<div id="qv">
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<h2>Quickview</h2>
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<ul>
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<li>Apps developed for Android 1.5 and below support only the baseline screen
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configuration, by default</li>
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<li>There are some simple steps you should take to enable support for multiple screens in
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an application designed for Android 1.5</li>
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</ul>
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<h2>In this document</h2>
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<ol>
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<li><a href="#strategies">Adding Multiple Screens Support</a></li>
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</ol>
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<h2>See also</h2>
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<ol>
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<li><a
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href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a></li>
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</ol>
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</div>
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</div>
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<p>All applications written for Android 1.5 or earlier, by default, support only the
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baseline HVGA screen used on the T-Mobile G1 and similar devices, which is <em>normal</em> screen
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size and medium density (<em>mdpi</em>). Android 1.6 introduced support for different screen
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configurations and added APIs that allow applications to control how they operate on different
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screens, using alternative resources for different screen configurations.</p>
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<p>If your manifest file includes the <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">{@code <uses-sdk>}</a> element,
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with the <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code android:minSdkVersion}</a>
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attribute set to {@code "3"} or lower, and does <em>not</em> include the <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
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android:targetSdkVersion}</a> set to {@code "4"} or higher, then this document is for you. By
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default, an application written for Android 1.5 or below that does not set the <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
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android:targetSdkVersion}</a> set to {@code "4"} or higher runs in <a
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href="screen-compat-mode.html">screen compatibility mode</a> when on a device with a screen larger than
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the
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<em>normal</em> screen size (basically, the system displays the application in a small window
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that is roughly the size of the normal screen size).</p>
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<p>This document describes how to get your application out of <a
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href="screen-compat-mode.html">screen compatibility
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mode</a> and instead support multiple screens, but also maintain compatibility with Android 1.5 and
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below.</p>
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<p class="note"><strong>Note:</strong> Before you begin, you should first decide whether it's even
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necessary to support Android 1.5. To see the relative number of devices that are still running
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Android 1.5, see the <a
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href="http://developer.android.com/about/dashboards/index.html">Platform Versions
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Dashboard</a>.</p>
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<h2 id="strategies">Adding Multiple Screens Support</h2>
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<p>If you have already developed and published an Android application based on
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Android 1.5 or earlier platform version, and want to maintain compatibility with Android 1.5, you
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need to make some changes to your application in order for it to properly run on newer devices with
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different screen configurations. You should be able to make these changes to your application such
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that you can distribute a single {@code .apk} to all devices.</p>
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<p>The recommended strategy is to develop your application against Android 1.6 (because it's the
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lowest version that includes support for multiple screens) and test your application on each
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platform version your application supports (especially the minimum platform, such as Android 1.5).
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Here's how to do that:</p>
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<ol>
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<li>Maintain compatibility with existing devices by leaving your application's <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code android:minSdkVersion}</a>
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attribute as it is. You <em>do not</em> need to increment the value of the attribute to support new
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devices and multiple screens. </li>
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<li>Extend compatibility for Android 1.6 (and higher) devices by adding <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
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android:targetSdkVersion}</a> to the <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html">{@code <uses-sdk>}</a> element.
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Set the value of <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#target">{@code
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android:targetSdkVersion}</a> to <code>"4"</code>. This allows your application to "inherit" the
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platform's multiple screens support, even though it is technically using an earlier version of the
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API.
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<p>Adding this attribute will cause an error in the compiler, because the attribute is unknown to
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Android 1.5. You'll fix this next.</p></li>
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<li>Change your application's build properties, such that it compiles against the Android 1.6 (API
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Level 4) library, rather than against the Android 1.5 (or earlier) library. You must do this in
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order for your application to successfully compile when using the new manifest attributes. Older
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versions of the platform simply ignore the attributes they don't know, so your application still
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runs fine on them, as long as you don't use APIs in your application code from Android 1.6. </li>
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</ol>
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<p>Your application is now prepared to run on multiple screens, while maintaining support for
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Android 1.5 or lower.</p>
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<p>Here's how you should begin testing your application:</p>
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<ol>
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<li>Set up AVDs for testing your application on Android 1.6 and some new versions. Create AVDs
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that use the screen sizes and densities that you want to support. When you create the AVDs, make
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sure to select the Android 1.6 or higher platform as the system image to use. For more information,
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see <a href="{@docRoot}guide/practices/screens_support.html#testing">How to Test Your Application on
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Multiple Screens</a>.</li>
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<li>Set up AVDs for testing your application on older versions of the platform, as low as the
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version declared by your <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code android:minSdkVersion}</a>.
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You need AVDs running the older platforms you are targeting, so that you can ensure there are
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no functional regressions.</li>
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<li>Compile your application against the Android 1.6 library and run it on the AVDs you created.
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Observe the way your application looks and runs, and test all of the user interactions.</li>
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<li>Debug any display or functional issues. For issues that you resolve in
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your application code, <span style="color:red">make certain not to use any APIs
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introduced later than the version declared by your <a
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href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#min">{@code
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android:minSdkVersion}</a></span>. If you
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are in doubt, refer to SDK reference documentation and look for the API Level specifier for the API
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you want to use. Using newer APIs not supported by your minimum version will mean that your
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application will no longer be compatible with devices running on that version.</li>
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</ol>
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<p>In particular, remember to test your application on an AVD that emulates a small-screen device.
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Users of devices with QVGA resolution at low density may want to download your application, so you
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should understand how your application will look and function on a small-screen device. In some
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cases, the reduced screen area and density mean that you need to make tradeoffs in design on those
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devices.</p>
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<p>Also give extra attention to testing your application on an AVD that emulates an <em>xlarge</em>
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screen. Devices with extra large screens are tablet-sized or larger, so you should pay close
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attention to how usable your application is on such screens. You might want to design new layouts
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specifically for extra large screens, to address usability aspects such as the location and size of
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buttons in your UI. To test your application on an extra large screen, create an AVD targeted to
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Android 3.0 and use the WXGA emulator skin.</p>
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<p>Once you've completed the procedures above, you should follow the recommendations in <a
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href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a> to add
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complete support for different screen configurations.</p>
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