UPDATE #3 (3/4/2015): Fixed a bug that caused a “completed” event to be triggered upon creating the progress ring. Now “completed” events will only be triggered by ring:goTo() calls made after the ring’s creation. Thanks to Nick for finding this mistake and pointing it out in the comments!

UPDATE #2 (1/23/2015): Fixed a bug that only manifests in Corona SDK build #2015.2544 and later. In build #2015.2544, Corona Labs fixed the finalize() bug that prevented objects’ finalize events from being triggered when their parent display group was removed. I had utilized a brilliant workaround developed by Sergey Lerg, but there was an error in my implementation of his fix that caused a crash when run on build 2015.2544 and later. I fixed that crash by adding a 1ms timer when checking to see if finalize events are being triggered as they should. The fix is not necessary for up-to-date Corona builds, but I’m leaving it in for folks who might be running legacy Corona builds.

UPDATE #1 (1/7/2015): The progressRing module has been updated to ensure that the procedurally-generated mask image reliably meets the requirements for mask images. Previously, it didn’t always work when running on devices whose screen size did not match up with the content width/height defined in an app’s config.lua file.

Something that is occasionally asked about on the Corona Labs forums is how to achieve a circular progress indicator (what I call a “progress ring”). The uses for this type of widget are limitless, but here are a few examples:

• player/enemy health bars in a RTS-style game (see Ravenmark)
• countdown timer to show when a player’s turn is up in a turn-based multiplayer or puzzle game
• a more visually interesting percentage indicator than the usual horizontal or vertical bar (in a business app)

A number of solutions have been proposed in the forums, often involving the use of sprite objects with X number of frames to cycle through depending on the position of the progress bar. These solutions can work, of course, but I set out to create my own progress ring solution with the following goals in mind:

• The movement of the progress ring should be seamless and smooth, regardless of which direction it was moving and/or how quickly (something that can’t happen with sprite-based solutions unless you use a prohibitively high number of frames)
• The progress ring must be created solely with code, so that it can be modularized into a single lua file and added to a project with one line of code (again, something that isn’t possible with sprite-based solutions).
• The progress ring must be visually customizable through code: colors, size, depth of the “donut hole” (or no donut hole at all), stroke width, etc.
• A progress ring object must have simple and easy-to-use methods for controlling it after it’s been created.

And I’m happy to report that I’ve come up with a solution that meets all those requirements and makes it very easy to add a progressRing to any Corona project with just one line of code! READ MORE »

As the “freemium” app monetization strategy has grown in popularity, many developers have encountered the same problem: how can we give away fully-unlocked copies of our app to reviewers or friends? Apple gives developers 100 free promo codes for each new version of an app to hand out, but Google Play does not, and even so those codes only help if your app doesn’t unlock features via in-app purchase (“IAP”). As of now there is no way for us to hand out IAP promo codes (though there are reports that this may change). To make matters worse, if you try to create your own system for unlocking features, the odds are very good that your app submission will be rejected by Apple’s reviewers. To the best of my knowledge, there’s nothing stopping you from creating your own IAP promo code system on Android, but who has time to create a whole menu system for unlocking content? Fortunately there is an easy way to unlock content on both iOS and Android simultaneously, with very little change to your code – and since this method is completely invisible, it does not trigger an App Store rejection! Read on to find out how… READ MORE »