Apache Flex (formerly Adobe Flex) is an open source application framework for building and maintaining expressive web applications that deploy consistently on all major browsers, desktops, and devices. It provides a modern, standards-based language and programming model that supports common design patterns suitable for developers from many backgrounds.
Apache Flex is an open-source SDK used to make rich Internet applications. It's developed with Action Script and MXML and works particularly well with Android and iOS ecosystems. Any flash-based application framework, such as Eclipse or the Flash above Builder, can be used to implement this. Free is best for mobile app developers, but suppose you have concerns, and consider Apache Flex's development team welcomes any questions via email.
Over the course of months/years, various security exploits and other issues are discovered and patched in AIR, often requiring you to rebuild and resubmit mobile apps to the various storefronts. This happens often enough that it's worth mentioning as a major con.
While development on Adobe AIR seems to be fairly constant, there is very little communication between the community and Adobe regarding the future and general support of AIR. The track record of Flash (and particularly Flash Mobile) does not inspire much confidence that Adobe intends to support Flash/AIR for years to come.
Adobe AIR does not seem to perform as well (in terms of raw performance, memory usage, framerates, responsiveness, etc.) as other hybrid solutions for certain tasks. For example using shaders tends to be experimental still, and graphic/animation intensive projects often require the use of third party frameworks such as Starling.
Although Adobe AIR is just an SDK without an actual "UI" it's commonly used within Flash, Flash Builder, or FlashDevelop. Considering the integration with Flash IDE, there are very few tools that can compete with its features.
Originally, Adobe AIR was the only game in town, and its blend of flexibility in platforms it could publish to (PC, Mac, iOS, Android), ease of use, and familiarity made it the clear choice. Now Adobe no longer supports it, and we’ve found the transition to Harmon unworkable for us.
Apache Flex is a modern, standards-based programming language that supports common design patterns. It's an open-source SDK used to make rich Internet applications that work on different browsers and platforms. Any flash-based application framework, such as Eclipse or the Flash above Builder, can be used to implement this. So far, in comparison, it's much more crucial, especially for people working in fields like mobile development.