Get Started « PhoneGap. Three20. Three20 is a open source Objective-C library used by dozens of well-known brands in the App Store, including Facebook, Posterous, Pulse, Meetup.com, and SCVNGR. Three20 provides powerful view controllers such as the Launcher, the popular Photo Browser, and internet-aware tables. The library is modular, meaning you choose which elements of the library to include in your app. This modular design allows Three20 to be one of the only Objective-C frameworks that encourages what are called 'extensions' from the community. You can explore some features of Three20 using the playable demo on the right. Three20 remembers your app's state so that you and your users don't have to. How does it work?
Each page in your app is treated as a distinct URL. Is this necessary now that multi-tasking is available? Your app can be shut down at any time. Example In the following example Jeff is posting a status update. Urban Airship - Powering Push Notifications, In-App Purchase, and Subscriptions for mobile applications across major mobile platforms.