Press, release and physics

Hi.

Could you give me some advice on how to do the following? :

- User taps screen and keeps finger on screen
- This moves a circle in an upward trajectory with acceleration

- User takes finger off screen
- This "releases" the circle to act under gravity
- Circle lands on a "floor" and decelerates to a stop

It's a bit of a vague description but any tips would be appreciated.

Something like this should work (this was typed from memory so there may be errors):

local physics = require("physics")
 
local H = display.contentHeight
local W = display.contentWidth
local centerX = W * 0.5
local centerY = H * 0.5
 
physics.start()
physics.setGravity(0,4)
 
local floor = display.newRect(0, 0, W, 50)
floor.x = centerX, floor.y = H
physics.addBody(floor, "static", {density=1.0, friction=0.5, bounce=0.2})
local circle = display.newCircle(centerX,100,50)
physics.addBody(circle, "dynamic", {density=1.0, friction=0.5, bounce=0.2, radius=50})
 
local onScreenTouch = function(event)
    if event.phase == "began" then
        -- You can play with the values to get the reaction you want
        circle:applyForce(
            -4, 0,
            circle.x, circle.y)
    end
end
 
Runtime:addEventListener("touch", onScreenTouch)

Nice one, thanks.

I'm playing around with changing the gravity after the user has stopped touching the screen and it seems to work. I'm using a second tap to replicate a fingerOff event.

What I can't work out is how to detect a "fingerOffScreen" event.

To detect when a finger has been lifted off the screen you have to another button phase. Add this to you button function.

1	elseif event.phase == "ended" then

Just add an "ended" event to the onScreenTouch function like this:

local onScreenTouch = function(event)
    -- This checks when the screen is touched
    if event.phase == "began" then
        -- You can play with the values to get the reaction you want
        circle:applyForce(
            -4, 0,
            circle.x, circle.y)
    -- This checks when the touch has ended
    elseif event.phase == "ended" then
        -- Put modified gravity settings here
        physics.setGravity(0,10)
    end
end

@Khaodik and @calebr2048

Thanks.

views:1342 update：2011/9/28 9:01:40


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