How to detect swipe direction?

[Terry Judd]

Thanks for the code Scott. On a related issue, I've tried a number of different approaches for implementing side-to-side swiping within a vertically scrolling group (a day-per-view calendar object) but haven't managed to come up with anything that works reliably - especially on iOS.

A combination of touchStart and touchRelease handlers works sort of OK on Android (touchMove and touchEnd messages don't seem to get sent reliably) but on iOS  I don't seem to be able to prevent the group from scrolling vertically if the swipe is more than a little bit off the horizontal.

Any ideas?

Terry...

On 07/10/2013, at 10:26 AM, Scott Rossi wrote:

> Hi Roger:
> 
> Might be wrong, but I don't believe there's a built-in swipe
> monitor/property.  I put together the following to detect course swipe
> direction and added the ability to track the swipe angle.  You can set the
> swipe distance threshold to control when an event is triggered from a
> swipe.  The code is written to place direction output in a field.
> 
> 
> -- 50 PIXEL SWIPE THRESHOLD
> 
> local hStart, vStart, theSwipeData
> local theThreshold = 50
> 
> on touchStart theID
>   put item 1 of mouseLoc() into hStart
>   put item 2 of mouseLoc() into vStart
> end touchStart
> 
> on touchmove theID, X, Y
>   put empty into theSwipeData
>   if Y > vStart and abs(vStart - Y) > theThreshold  then put "down,"
> after theSwipeData
>   if Y < vStart and abs(vStart - Y) > theThreshold  then put "up," after
> theSwipeData
>   if X > hStart and abs(hStart - X) > theThreshold  then put "right,"
> after theSwipeData
>   if X < hStart and abs(hStart - X) > theThreshold  then put "left,"
> after theSwipeData
>   if theSwipeData is not empty then put locToAngle(X,Y,hStart,vStart)
> after theSwipeData
> end touchmove
> 
> on touchEnd theID
>   put "swipe: " into theResult
>   if theSwipeData is not empty then put theSwipeData after theResult
>   set text of fld 1 to theResult
> end touchEnd
> 
> function locToAngle pX,pY,pXorigin,pYorigin
>   put atan2(pY - pYorigin,pXorigin - pX) into R
>   return round(180+(R*(180/pi)))
> end locToAngle
> 
> 
> 
> 
> 
> Hope this helps.
> 
> Regards,
> 
> Scott Rossi
> Creative Director
> Tactile Media, UX/UI Design
> 
> 
> 
> 
> On 10/6/13 2:09 PM, "Roger Eller" <roger.e.eller at sealedair.com> wrote:
> 
>> I want a different action to occur based on the direction the user swipes
>> a
>> control.  For example:
>> 
>>  on swipeLeft
>>       set the backgroundColor of me to red
>>  end swipeLeft
>> 
>>  on swipeRight
>>       set the backgroundColor of me to green
>>  end swipeRight
>> 
>> Is there a one liner on mobile that can give me the direction, or
>> true/false, or l/r/u/d?
>> 
>> ~Roger
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Dr Terry Judd
Senior Lecturer in Medical Education
Medical Education Unit
Faculty of Medicine, Dentistry & Health Sciences
The University of Melbourne