page.title=Backwards Compatibility
@jd:body

<p>Significant changes in Android 3.0 included:</p>
<ul>
<li>Deprecation of navigation hardware keys (Back, Menu, Search, Home) in favor of handling navigation
  via virtual controls (Back, Home, Recents).</li>
<li>Robust pattern for the use of menus in action bars.</li>
</ul>
<p>Android 4.0 brings these changes for tablets to the phone platform.</p>

<h2 id="older-hardware">Adapting Android 4.0 to Older Hardware and Apps</h2>

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<h4>Phones with virtual navigation controls</h4>
<p>Android apps written for Android 3.0 and later display actions in the action bar. Actions that don't
fit in the action bar or aren't important enough to be displayed at the top level appear in the
action overflow.</p>
<p>Users access the action overflow by touching it in the action bar.</p>

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    <img src="{@docRoot}design/media/compatibility_virtual_nav.png">

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<h4>Phones with physical navigation keys</h4>
<p>Android phones with traditional navigation hardware keys don't display the virtual navigation bar at
the bottom of the screen. Instead, the action overflow is available from the menu hardware key. The
resulting actions popup has the same style as in the previous example, but is displayed at the bottom of the screen.</p>

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    <img src="{@docRoot}design/media/compatibility_physical_buttons.png">

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<h4>Legacy apps on phones with virtual navigation controls</h4>
<p>When you run an app that was built for Android 2.3 or earlier on a phone with virtual navigation
controls, an action overflow control appears at the right side of the virtual navigation bar. You
can touch the control to display the app's actions in the traditional Android menu styling.</p>

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    <img src="{@docRoot}design/media/compatibility_legacy_apps.png">

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