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Leafcutter
Leafcutter
Inspiring
September 1, 2011
Question

Small fingers and mouse events

  • September 1, 2011
  • 1 reply
  • 393 views

We recently released an AIR app for kids where they can use their fingers to draw letters.  During testing we observed that the mouseMove event sometimes failed as a child moved their finger across the screen.  Doing a bit more observation it appears that when drawing if the child rotates their finger so that it is mostly the side of the finger that touches the screen (quite easy to do if you are tracing a letter shape) then 'contact' is lost.  Initially I assumed that the child must be removing their finger from the screen but this wasn't the case.

When you do the same thing with an adult finger then the problem doesn't happen.

I tried this on two different android devices (Desire and a Galaxy tab) and both had the same results.  The same small finger on the same app written natively on iPad didn't have this problem.

Is there a minimum radius of touch that is required before AIR treats it as a mouse touch or is this possibly a hardware sensitivity issue?  It isn't a showstopper (the kid can learn to keep the pad of their finger onscreen) but I thought it was interesting to see if anyone had any ideas.

This topic has been closed for replies.

1 reply

A
Anonymous
September 1, 2011

I would guess the problem is not the finger size because these screen scan detect the smallest amount of pressure, at least iPhone screens. I am guessing since its mouse event having more than one touch point cancels it out. Try it yourself, hold one finger on the screen then use the other to touch the button in question, it wont respond. But if you only touch with one finger it works fine.

Your solution to that is to switch to a touch event, there is a code snippet for that, what that allows you to do is track multiple fingers at once so even if a child is holding the phone with one hand with their thumb on the screen or not being super careful with his touches it will still work.

Leafcutter
LeafcutterAuthor
Inspiring
September 1, 2011

I also thought it might be that another finger (or part of hand) was touching the screen but it doesn't seem to be.  Once you have made contact with the screen (mouse_down) and are moving continuously (mouse_move) then you can tap the screen elsewhere and the contact isn't broken.

If you tap very close to the initial tap (within maybe a 1cm radius) then you can confuse the sensor as to where the mouse move is actually occuring - I assume there is some kind of test that assumes if a new mouse move is close to the last move then it is the same move.  I think I managed to rule out multiple touches during testing though - the device was held steady on a table and the user was just using a pointed finger, so visually at least there was nothing else in contact with the screen.

Maybe I will have to do more observation to see if I can get to the bottom of it.

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