prevent from dragging a shape over other shape

newwork01 · April 2014

Hi Everyone,
Im new to gideros . In Drag Me Example, I want to prevent from dragging a shape over other shape ( means it will stop when hit other shape ) . How can i implement the code ?

hgvyas123 · April 2014

You can try TntCollision Engine or

http://giderosmobile.com/forum/discussion/121/simple-collision-detection/p1

to check for the collision if they collide stop moving them else allow

ar2rsawseen · April 2014

@hgvyas123 unfortunately thats not that easy, if you determine that they collide and stop move them, then you can't also move the figure back from the collided figure, because you will be ignoring all movements.

You also need to take an account the side of collision, the vector, etc.

more and more I started thinking that it might be easier to implement through dragging box2d bodies, unless I'm missing some obvious solution

http://appcodingeasy.com/Gideros-Mobile/Dragging-Box2d-object-in-Gideros-Mobile

hgvyas123 · April 2014

hmmm right little tweak needed here is the solution

--[[
Drag the shapes around with your mouse or fingers
This code is MIT licensed, see <a href="http://www.opensource.org/licenses/mit-license.php" rel="nofollow">http://www.opensource.org/licenses/mit-license.php</a>
(C) 2010 - 2011 Gideros Mobile
]]
 
local myShapes = {}
 
function Sprite:collidesWith(sprite2)
	local x,y,w,h = self:getBounds(stage)
	local x2,y2,w2,h2 = sprite2:getBounds(stage)
 
	return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2))
end
 
local function onMouseDown(self, event)
  if self:hitTestPoint(event.x, event.y) then
    self.isFocus = true
    self.x0 = event.x
    self.y0 = event.y
 
    event:stopPropagation()
  end
end
 
local function onMouseMove(self, event)
  if self.isFocus then
    self.lastX,self.lastY = self:getPosition()
	local dx = event.x - self.x0
    local dy = event.y - self.y0
    self:setX(self:getX() + dx)
    self:setY(self:getY() + dy)
    self.x0 = event.x
    self.y0 = event.y
	for i=1,#myShapes do
		if myShapes[i] ~= self then
			if self:collidesWith(myShapes[i]) then
				self:setPosition(self.lastX,self.lastY)
			end
 
		end
	end
 
    event:stopPropagation()
  end
end
 
local function onMouseUp(self, event)
  if self.isFocus then
    self.isFocus = false
 
    event:stopPropagation()
  end
end
 
 
for i=1,5 do
  local shape = Shape.new()
  shape:setLineStyle(3, 0x000000)
  shape:setFillStyle(Shape.SOLID, 0xff0000, 0.5)
  shape:beginPath()
  shape:moveTo(0, 0)
  shape:lineTo(100, 0)
  shape:lineTo(100, 50)
  shape:lineTo(0, 50)
  shape:closePath()
  shape:endPath()
 
  shape:setX(math.random(0, 320 - 100))
  shape:setY(math.random(0, 480 - 50))
 
  shape.isFocus = false
 
  shape:addEventListener(Event.MOUSE_DOWN, onMouseDown, shape)
  shape:addEventListener(Event.MOUSE_MOVE, onMouseMove, shape)
  shape:addEventListener(Event.MOUSE_UP, onMouseUp, shape)
 
  stage:addChild(shape)
  table.insert(myShapes,shape)
end
 
local info = TextField.new(nil, "drag the shapes around with your mouse or fingers")
info:setPosition(23, 50)
stage:addChild(info)

hgvyas123 · April 2014

basically i store position of shape before moving it and later i check whether it collides or not and if they collide i reset shape's position to last stored value

ar2rsawseen · April 2014

@hgvyas123 hmm, yes that is a nice workaround, kudos!

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