使用 Corona SDK 调整运动的物理实体大小

我一直在尝试创建一个简单的游戏，玩家控制物理主体，在与其他物体碰撞时会增加大小。据我所知，直接缩放实际的物理主体是不可能的，因此我正在尝试使用原始物理主体的参数创建一个新的物理主体。然而，当创建一个适当大小的新物理主体时，我失去了移动它的能力。任何形式的输入将非常感激，因为我不知道该怎么做（我仍然很新手）。

到目前为止，这是我拥有的东西：

function movePlayer(event)

if "began" == event.phase then
    player.isFocus = true

    player.x0 = event.x - player.x
    player.y0 = event.y - player.y
elseif player.isFocus == true then
    if "moved" == event.phase then
        player.x = event.x - player.x0
        player.y = event.y - player.y0
        stayOnScreen( player )
    elseif "ended" == phase or "cancelled" == phase then
        player.isFocus = false
    end
end

return true
end

function checks()

if player.resize == true then
    local player2 = createPlayer(player.x, player.y, player.xScale, player.yScale, player.rotation)

    if player.isFocus == true then
        player2.isFocus = player.isFocus
        player2.x0 = player.x0
        player2.y0 = player.y0
    end
    player2.resize = false
    player:removeSelf()
    player = player2
end
end

player:addEventListener("touch", movePlayer)
Runtime:addEventListener( "enterFrame", checks)

提前感谢！

编辑： 这是生成一个新玩家并添加物理主体的代码：

function createPlayer( x, y, xScale, yScale, rotation)
local player = display.newImageRect("images/p1.png", 71, 71)
player.x = x
player.y = y
player.xScale = xScale
player.yScale = yScale

local playerCollisionFilter = { categoryBits = 2, maskBits = 5 }
local playerBodyElement = { filter=playerCollisionFilter, radius = (player.xScale * (player.width *0.5)) }

player.objectType = "player"
physics.addBody ( player, "dynamic", playerBodyElement )
player.isBullet = true
player.isSleepingAllowed = false
player.rotation = rotation
player.resize = false

return player
end