Forward or Backward Compatibility in Android?

问题:

I would like to know whether the Android provides any sort of compatibility i.e either forward or backward. It means as in Blackberry if develop an Application with JDE 4.2 then that application will work on any handset with OS 4.2 or higher which means it has forward compatibility. Is there anything similar in Android?

Suppose I develop application with Android SDK 1.5 then will that application work on any handset having OS 1.5 or higher.

Hope to get a reply soon.

Thanks & Regards Sunil

回答1:

Forward compat is somewhat assured on major versions. On Android you target a minimum api spec. As long as your are not calling private APIs, Google keeps compatibility going forward on devices that join in on their Open Mobile Alliance.

It doesn't mean someone can't get the Android source and release an Android based OS of their own that breaks all compatibility. These devices wouldn't get Google's Market Place because only licensed devices that Google tests get to use that. If that is where you are releasing, you probably won't have any trouble.

回答2:

Because the Android documentation is licensed under the Apache license, I'm comfortable quoting a large section:

Android applications are generally forward-compatible with new versions of the Android platform.

Because almost all changes to the framework API are additive, an Android application developed using any given version of the API (as specified by its API Level) is forward-compatible with later versions of the Android platform and higher API levels. The application should be able to run on all later versions of the Android platform, except in isolated cases where the application uses a part of the API that is later removed for some reason.

Forward compatibility is important because many Android-powered devices receive over-the-air (OTA) system updates. The user may install your application and use it successfully, then later receive an OTA update to a new version of the Android platform. Once the update is installed, your application will run in a new run-time version of the environment, but one that has the API and system capabilities that your application depends on.

...

Android applications are not necessarily backward compatible with versions of the Android platform older than the version against which they were compiled.

Each new version of the Android platform can include new framework APIs, such as those that give applications access to new platform capabilities or replace existing API parts.

-- From: http://developer.android.com/guide/topics/manifest/uses-sdk-element.html

Though they are forward compatible, Android apps will not be able to use features of the SDK that were introduced after they were written, not surprisingly.

回答3:

That's not what "forwards compatibility" means. You are thinking of "backwards compatibility". "Backwards compatibility" means that new versions of the platform (i.e. Android) will still run old software developed against an older version of the platform. "Forwards compatibility" is the precise converse -- older software developed against an older version of the platform will still be able to leverage new features of the new platform.

An example of backwards compatibility is that they rename one of the methods in ICS but still implement a deprecated version of the old method and have it forward to the new implementation.

While backwards compatibility is almost always guaranteed, forwards compatibility is only guaranteed in certain scenarios. An example of forward compatibility would be a situatation where they implement a new feature in the OS (for example, "pinch to zoom") and applications written before that feature existed are still able to enjoy this feature.

回答4:

I think Android System is backward-compatible, and that ensures the forward compatibility of Android application.