3.10. Application Badges

With the iPhone’s numerous different connections—3G/EDGE, WiFi, and Bluetooth—lots of things can happen while you’ve got that little device stuck in your pocket. Without some notification to the user that there are pending notifications, he’s likely to miss everything that’s happened while he was busy having a real life. As new features appear in iPhone firmware, such as push notification, your application may receive new information when it is not in the foreground. In addition to this, application badges can serve as a reminder to a user who has run the application but did not finish viewing all messages, notifications, or other data. Application badges are small message bubbles that appear on the program’s home screen icon. Application badges are used heavily by Apple’s preloaded applications to alert the user to missed calls, voicemail, text messages, and email.

One of the nice features about these types of badges is that the application doesn’t necessarily need to be running for the badge to display on the springboard. This is useful in serving as a reminder to the user even after he has exited the application. This also means you’ll need to clean up any lingering badges when your program exits.