[android-developers] Re: MotionEvent HistorySize and multiple Pointers

Hi Dianne,

> (Also, even caring about the historical data is rare.  If all you need is
> the most recent positions, just ignore the historical data.)

Is the historical data device dependent? So are there any devices that
always set the amount to 0?

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.

Thanks

On Oct 16, 12:54 am, Dianne Hackborn <hack...@android.com> wrote:
> (Also, even caring about the historical data is rare.  If all you need is
> the most recent positions, just ignore the historical data.)
>
> On Fri, Oct 15, 2010 at 3:54 PM, Dianne Hackborn <hack...@android.com>wrote:
>
>
>
>
>
> > Just think of this as a two dimensional array.  A MotionEvent contains N
> > pointers.  That MotionEvent may also have M historical positions each
> > containing another N pointers that exactly match the identifiers of the most
> > recent pointers in the event.
>
> > On Fri, Oct 15, 2010 at 2:42 PM, Julio Suarez <j.gato...@gmail.com> wrote:
>
> >> Hi,
>
> >> Have you figured this out yet? I too am very confused as to how to
> >> handle Historical points when more the one pointer is on the screen. I
> >> have no idea how to separate what and how much historical data goes
> >> with each pointer.
>
> >> On Aug 22, 6:23 pm, sztupy <szt...@googlemail.com> wrote:
> >> > I couldn't find a definite reference for the size of a MotionEvents
> >> > history, when there are multiple pointers. The reference says that if
> >> > you use a getHistorical* function, you might pass it a history
> >> > position which is somewhere between [0..getHistorySize()-1]. But in a
> >> > lot of examples handlingmultitouchif there are multiple pointers
> >> > they only use history positions between [0..getHistorySize()/
> >> > getPointers()-1] (so they divide the history's size with the number of
> >> > pointers). Which one is the correct way?
>
> >> >  SztupY
>
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> > --
> > Dianne Hackborn
> > Android framework engineer
> > hack...@android.com
>
> > 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.
>
> --
> Dianne Hackborn
> Android framework engineer
> hack...@android.com
>
> 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.

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