So, I carried out a little experiment to prove to myself that historical data is "lost" because you can only get historical data on MOVE_ACTION. Here's what I did:
I used the debug logging to log all touch positions and also historical positions. Let's say you have the following sequence of events occur with a single pointer: DOWN,MOVE,MOVE,MOVE,UP I notice that I'll have like 3 historical positions between DOWN/MOVE, and all the MOVE/MOVE transitions. However, by design there isn't any historical data between MOVE/UP. So any Move data that may have come in from the touch hardware before the actual UP event, is lost. It's probably not important, but it is definitely lost. On Oct 19, 5:12 pm, Julio Suarez <[email protected]> wrote: > So you're saying that if I get an event with a pointer count of say 2 > (using event.getPointerCount()), and let's say that > event.getHistorySize returns 5. This means there are absolutely 10 > historical positions in total? There isn't a case where say, pointer 1 > will have 5 historical positions, and say pointer 2 only has 2 > historical positions? > > Thanks, > > On Oct 16, 7:14 pm, Dianne Hackborn <[email protected]> wrote: > > > On Sat, Oct 16, 2010 at 1:08 AM, webmonkey <[email protected]> wrote: > > > Is the historical data device dependent? So are there any devices that > > > always set the amount to 0? > > > Er. Not sure what you mean. It is just any data that has occurred since > > the last motion event and the most recent positions in the current one. It > > depends on how fast hardware generates data, how fast the apps consumes > > data, etc. > > > > Historical data is mostly used for smooth painting, see: > > > >http://corner.squareup.com/2010/07/smooth-signatures.html > > > > Works great on the Nexus One. But if other devices do not use this or > > > if this gets deprecated that would be nice to know for the future. > > > This is part of the API. It just lets you get all of the intermediate data > > coming from the touch screen. I can't make guarantees about every possible > > piece of hardware in the future, though of course I would generally expect > > touch screens to generate at least 60fps of data when there is only one > > finger down. > > > -- > > Dianne Hackborn > > Android framework engineer > > [email protected] > > > Note: please don't send private questions to me, as I don't have time to > > provide private support, and so won't reply to such e-mails. All such > > questions should be posted on public forums, where I and others can see and > > answer them. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
