In the days of the first Android G1 phone, a patch to the Android 1.0 OS circulated among developers to enable the multitouch screen on the device. The word was that it was a little buggy, there were no applications for it, and normal users should avoid it.
In Android 2.0, multitouch was officially added to the OS. I wondered why a slew of multitouch applications didn't immediately follow this release; I found out the reason when I read through the new multitouch chapter in the beta 2 PDF of the book "Hello, Android, 3rd Edition" by Ed Burnette.
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This warning box from the book sums up the issue:
Warning: multibugs ahead
Multitouch, as implemented on current Android phones, is extremely buggy. In fact it’s so buggy that it borders on the unusable. The API routinely reports invalid or impossible data points, especially during the transition from one finger to two fingers on the screen and vice versa. On the developer forums you can find complaints of fingers getting swapped, x and y axes flipping, and multiple fingers sometimes being treated as one. With a lot of trial and error, I was able to get the example in this chapter working because the gesture it implements is so simple. Until Google acknowledges and fixes the problems, that may be about all you can do. Luckily, pinch zoom seems to be the only multitouch gesture most people want.
Burnette then goes on to write an image viewer example that uses the pinch-zoom gesture. The event stream he dumps as he debugs the application reveals the unreliability of the API, but he manages to implement pinch-zoom by doing some fairly detailed analysis in the application. Even then, he warns that his application will be buggy if the user lets his or her fingers get within an inch of each other.
The lesson: Caveat coder. ;)
This article, "Why Google Android developers should avoid multitouch," was originally published at InfoWorld.com. Read more of Martin Heller's Strategic Developer blog and follow the latest news in Google Android and software development at InfoWorld.com.