Strategies for Android 1.5

All applications written for Android 1.5 or earlier, by default, support only the baseline HVGA screen used on the T-Mobile G1 and similar devices, which is normal screen size and medium density (mdpi). Android 1.6 introduced support for different screen configurations and added APIs that allow applications to control how they operate on different screens, using alternative resources for different screen configurations.

If your manifest file includes the <uses-sdk> element, with the android:minSdkVersion attribute set to "3" or lower, and does not include the android:targetSdkVersion set to "4" or higher, then this document is for you. By default, an application written for Android 1.5 or below that does not set the android:targetSdkVersion set to "4" or higher runs in screen compatibility mode when on a device with a screen larger than the normal screen size (basically, the system displays the application in a small window that is roughly the size of the normal screen size).

This document describes how to get your application out of screen compatibility mode and instead support multiple screens, but also maintain compatibility with Android 1.5 and below.

Note: Before you begin, you should first decide whether it's even necessary to support Android 1.5. To see the relative number of devices that are still running Android 1.5, see the Platform Versions Dashboard.

Adding Multiple Screens Support

If you have already developed and published an Android application based on Android 1.5 or earlier platform version, and want to maintain compatibility with Android 1.5, you need to make some changes to your application in order for it to properly run on newer devices with different screen configurations. You should be able to make these changes to your application such that you can distribute a single .apk to all devices.

The recommended strategy is to develop your application against Android 1.6 (because it's the lowest version that includes support for multiple screens) and test your application on each platform version your application supports (especially the minimum platform, such as Android 1.5). Here's how to do that:

1. Maintain compatibility with existing devices by leaving your application's android:minSdkVersion attribute as it is. You do not need to increment the value of the attribute to support new devices and multiple screens.
2. Extend compatibility for Android 1.6 (and higher) devices by adding android:targetSdkVersion to the <uses-sdk> element. Set the value of android:targetSdkVersion to "4". This allows your application to "inherit" the platform's multiple screens support, even though it is technically using an earlier version of the API.

   Adding this attribute will cause an error in the compiler, because the attribute is unknown to Android 1.5. You'll fix this next.

3. Change your application's build properties, such that it compiles against the Android 1.6 (API Level 4) library, rather than against the Android 1.5 (or earlier) library. You must do this in order for your application to successfully compile when using the new manifest attributes. Older versions of the platform simply ignore the attributes they don't know, so your application still runs fine on them, as long as you don't use APIs in your application code from Android 1.6.

Your application is now prepared to run on multiple screens, while maintaining support for Android 1.5 or lower.

Here's how you should begin testing your application:

1. Set up AVDs for testing your application on Android 1.6 and some new versions. Create AVDs that use the screen sizes and densities that you want to support. When you create the AVDs, make sure to select the Android 1.6 or higher platform as the system image to use. For more information, see How to Test Your Application on Multiple Screens.
2. Set up AVDs for testing your application on older versions of the platform, as low as the version declared by your android:minSdkVersion. You need AVDs running the older platforms you are targeting, so that you can ensure there are no functional regressions.
3. Compile your application against the Android 1.6 library and run it on the AVDs you created. Observe the way your application looks and runs, and test all of the user interactions.
4. Debug any display or functional issues. For issues that you resolve in your application code, make certain not to use any APIs introduced later than the version declared by your android:minSdkVersion. If you are in doubt, refer to SDK reference documentation and look for the API Level specifier for the API you want to use. Using newer APIs not supported by your minimum version will mean that your application will no longer be compatible with devices running on that version.

In particular, remember to test your application on an AVD that emulates a small-screen device. Users of devices with QVGA resolution at low density may want to download your application, so you should understand how your application will look and function on a small-screen device. In some cases, the reduced screen area and density mean that you need to make tradeoffs in design on those devices.

Also give extra attention to testing your application on an AVD that emulates an xlarge screen. Devices with extra large screens are tablet-sized or larger, so you should pay close attention to how usable your application is on such screens. You might want to design new layouts specifically for extra large screens, to address usability aspects such as the location and size of buttons in your UI. To test your application on an extra large screen, create an AVD targeted to Android 3.0 and use the WXGA emulator skin.

Once you've completed the procedures above, you should follow the recommendations in Supporting Multiple Screens to add complete support for different screen configurations.