Are android apps backwards compatible?

Should I build an app that targets Android 2.2 and release it on the Android Marketplace;

Would the app be available for download and use on devices running a version of Android OS lower than the targeted version of the app? - Let's say Android OS version 1.6.

What would happen if a user (with an Android OS version 1.6 powered devic开发者_高级运维e) were to attempt to run the app?

Would they be prompted to update their OS or just receive an error message?

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It depends what you have in the minSdkVersion field in your AndroidManifest.xml. If it is set to 4 or lower, then it will be visible to people using 1.6.

There's a good explanation here.

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The android SDK is completely backward compatible using the mechanism that @Graham mentions. The other question will be "how far should you go". Use this graph to see the population of users on each platform level.

http://developer.android.com/resources/dashboard/platform-versions.html

This is pure opinion, but I would advise starting your app at API levels 7 or 8. The benefits of the APIs in EClair+ are worth losing this 0.4% still on 1.x devices.

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If you are targeting 2.2, users with earlier SDK will not be able to download it.

They will see: This app is Incompatible with your device XXXXXXX