Multitouch - Only do function when two fingers are touching?

Hi, i have tried to read and checked samples but I haven't figured this out.

I have a function but I only want to do it when 2 fingers are touching the object.

Anyone got a good way to check if two fingers are touching the object?

Posted this in the "New Users Start Here"-forum but i think it's better here...
Thanks Joel

Good question, Joel. Take a look at the Interface/PinchZoomGesture sample app in the Corona SDK. It demonstrates how to use multitouch, touch event IDs, etc, to track the number of touches on a object.

Tim

Hi Tim,
I have looked at it, and i tried to figure it out but I'm confused. Is there anyway tonget somekind of api that can handle event[id].phase == "moving" then
Like id = the number of fingers touching the screen..

If two fingers touching id = 2, if three fingers touching then id = 3?

That way you could easily check for # of fingers touching.

Also the pinchzoomgesture is for three fingers on Android. You don't happen to know what variable i need to change for only two fingers, because the first finger doesn't add any interaction to the application running...

Thanks Joel

I also want to know this, was this thread abandoned?!

Another problem(?), if i activate multitouch on my app, in the emulator nothing is touchable. Why? Is this because two fingers have to touch at the same time, why?

Edit: Hm, this might be a PC/MAC problem. Now on the MAC at work it works fine but home on the PC it won't work.

Here's a quick attempt at using a table to track the number of touches on an object. You need to test this on a device, obviously, not in the simulator.

system.activate( "multitouch" )
 
local box = display.newRect( 0, 0, 320, 480)
local touches = {}
local debug = display.newText("Number of fingers down:", 20, 30, system.nativeFont, 16)
debug:setTextColor(0, 0, 0)
 
function onTouch( event )
 
    local target = event.target
    local id = event.id
    local phase = event.phase
    
    if phase == "began" then
        table.insert(touches, id)
    elseif phase == "ended" or phase == "cancelled" then
        for i,v in ipairs(touches) do
            if touches[i] == id then
                table.remove(touches, i)
            end
        end
    end
 
    debug.text = "Number of fingers down: " .. #touches
        
end
 
box:addEventListener('touch', onTouch)

I was messing around with this the other day. The key thing you need to know is that for multi touch events u will get a second event, even if the first one hasn't ended. i.e. two "begin" events (one for each finger) before any "end" event. Therefore you need to track the first finger and see if there was every another one BEFORE it was lifted (ended).

Since you normally use both fingers attributes, like 'x' to do things you usually want to store that information in a table, so you can access it. Thats what the example does.

However if all you want to do is say move a shape with two fingers you don't need to bother storing the second event stuff.

Here's an example that will let you do whatever you like using the FIRST fingers co-ordinates, but only if more than one finger is down. You could add if t.numberToucher == 1, or 2 , or 3 (at the point i marked with a (*), if you want to do different things for different amount of fingers down,

Remember this only tracks information of the first finger tho. For things like pinch zoom etc where u need to know the distance between fingers you need to store that information.

Hope it helps.

onTouch = function( event )
 
        local t = event.target
        local phase = event.phase
        
        if "began" == phase then
                        if t.numberTouches == nil then
                                -- First finger touch, initialise
                                t.numberTouches = 1
                                t.multiTouch = false
                                t.firstFingerEvent = event.id
                        else
                                -- More than 1 finger, increase count
                                t.multiTouch = true
                                t.numberTouches = t.numberTouches + 1
                        end
                
                elseif ("move" == phase ) then
                        -- Check for multitouch, and that this is the move for the first finger
                        if t.multiTouch then
                                if event.id = t.firstFingerEvent then   
                                        -- (*) all coordinates etc of event are of the FIRST finger.  Do whatever you want here
                                        -- eg. movesomething(event.x, event.y)   
                                end
                        else
                                -- Do whatever for single touches
                        end
                        
                elseif ("ended" == phase or "cancelled" == phase) and t.x0 ~= nil and t.y0 ~= nil then
                        t.numberTouches = t.numberTouches - 1
                        if t.numberTouches == 0 then 
                                t.numberTouches = nil   -- All touches done nil out for next time
                        end
                
                        if not t.multiTouch then
                                t.numberTouches = nil           -- All touches done nil out for next time
                                -- Do whatever for single touches
                        end
                end
end
<code>

Ok, will try!
Thanks!

views:2697 update：2011/10/9 9:57:41


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