要拥有与物理交互的可拖动物体，您需要使用触摸关节。正如 krs 所提到的，您可以使用“CoronaSDK/SampleCode/Physics/MultiPuck”示例开始。触摸关节的运动确实有一点弹性，它们跟不上触摸事件。
local physics = require("physics")
physics.start()
physics.setGravity(0,0)
physics.setDrawMode("normal")
local source
function move( event )
local body = event.target
local phase = event.phase
local stage = display.getCurrentStage()
if "began" == phase then
stage:setFocus( body, event.id )
body.isFocus = true
-- Create a temporary touch joint and store it in the object for later reference
if params and params.center then
-- drag the body from its center point
body.tempJoint = physics.newJoint( "touch", body, body.x, body.y )
else
-- drag the body from the point where it was touched
body.tempJoint = physics.newJoint( "touch", body, event.x, event.y )
end
elseif body.isFocus then
if "moved" == phase then
-- Update the joint to track the touch
body.tempJoint:setTarget( event.x, event.y )
elseif "ended" == phase or "cancelled" == phase then
stage:setFocus( body, nil )
body.isFocus = false
-- Remove the joint when the touch ends
body.tempJoint:removeSelf()
end
end
-- Stop further propagation of touch event
return true
end
local target = display.newCircle( 250, 250, 60 )
target.x = display.contentCenterX
target.y = display.contentCenterY
target:setFillColor(240, 200, 0)
physics.addBody(target,"dynamic",{radius = target.width / 2})
source = display.newCircle( 250, 250, 60 )
source.x = display.contentCenterX
source.y = display.contentHeight - 100
source:setFillColor( 240,125,0 )
physics.addBody(source,"dynamic",{radius = target.width / 2})
source:addEventListener( "touch", move)
如果您不想要 Touch 关节的弹性并且希望您的圆盘移动得与用户的触摸一样快，您必须自己进行一些物理操作。你需要计算触球的速度来确定力和冲击的方向来确定推球的方向。
local sqrt = math.sqrt
local physics = require("physics")
physics.start()
physics.setGravity(0,0)
physics.setDrawMode("debug")
local source
local target
-- Track velocity
local velocityTracker = {
points = {}
}
function velocityTracker:reset()
self.points = {}
end
function velocityTracker:addPoint(time, x, y)
-- Only keep 10 points
local count = #self.points + 1
if count == 11 then
count = 10
for i=1,10 do
-- Move older points to top
self.points[i] = self.points[i+1]
end
end
self.points[count] = {time = time, x = x, y = y}
end
function velocityTracker:getVelocity(moves)
if #self.points < 2 then
return 0
end
local start = self.points[1]
local totalVelocity = 0
local now = system.getTimer()
for i=2,#self.points do
local finish = self.points[i]
-- Use a vector to determine velocity
local timePassed = finish.time - start.time
local age = now - finish.time
-- Only use recent points
if age < 200 then
local vector = {x = finish.x - start.x, y = finish.y - start.y}
local distance = sqrt(vector.x^2 + vector.y^2)
-- Calculate velocity
totalVelocity = totalVelocity + (distance / timePassed)
end
start = finish
end
return totalVelocity
end
local function onPuckCollision( event )
if event.phase == "began" and event.other.isBall then
-- Puck just hit a ball
local ball = event.other
local puck = event.target
-- Use a vector to determine direction of hit
local vector = {x = ball.x - puck.x, y = ball.y - puck.y}
-- normalize vector
local magnitude = sqrt(vector.x^2 + vector.y^2)
if magnitude > 0 then
vector.x = vector.x / magnitude
vector.y = vector.y / magnitude
end
-- Use velocity to determine force
local force = 10 * velocityTracker:getVelocity()
local function smack()
ball:applyForce(vector.x * force, vector.y * force, ball.x, ball.y)
end
-- We can't modify phyiscs in a collision handler so we
-- `performWithDelay` to cause it to execute after this function
timer.performWithDelay(0, smack)
end
end
local function movePuck( event )
local t = event.target
local phase = event.phase
if "began" == phase then
local parent = t.parent
display.getCurrentStage():setFocus( t )
t.isFocus = true
-- Store initial position
t.x0 = event.x - t.x
t.y0 = event.y - t.y
-- Save velocity tracking state
velocityTracker:reset()
velocityTracker:addPoint(event.time, event.x, event.y)
elseif t.isFocus then
if "moved" == phase then
t.x = event.x - t.x0
t.y = event.y - t.y0
-- Track a movement
velocityTracker:addPoint(event.time, event.x, event.y)
elseif "ended" == phase or "cancelled" == phase then
display.getCurrentStage():setFocus( nil )
t.isFocus = false
velocityTracker:reset()
end
end
return true
end
target = display.newCircle( 250, 250, 60 )
target.x = display.contentCenterX
target.y = display.contentCenterY
target:setFillColor(240, 200, 0)
target.isBall = true
-- Don't allow sleeping because a moving static body
-- won't always wake it if it's asleep
target.isSleepingAllowed = false
physics.addBody(target,"dynamic",{radius = target.width / 2})
source = display.newCircle( 250, 250, 60 )
source.x = display.contentCenterX
source.y = display.contentHeight - 100
source:setFillColor( 240,125,0 )
source.isPuck = true
-- Use static body if you're going to move the object instead of
-- letting the physics engine move it
physics.addBody(source,"static", {radius = source.width / 2})
source:addEventListener("collision", onPuckCollision)
source:addEventListener("touch", movePuck)
local bounds = {
left = -target.width,
top = -target.height,
right = display.contentWidth + target.width,
bottom = display.contentHeight + target.height,
}
-- Reset ball position if it leaves screen
local function resetBall()
if target.x < bounds.left or target.x > bounds.right or
target.y < bounds.top or target.y > bounds.bottom
then
target.bodyType = 'static' -- Stop current movement
target.x = display.contentCenterX
target.y = display.contentCenterY
target.bodyType = 'dynamic' -- Make movable again
source.x = display.contentCenterX
source.y = display.contentHeight - 100
display.getCurrentStage():setFocus( nil )
end
end
timer.performWithDelay(500, resetBall, 0)