Corona SDK屏幕过渡效果未生效。

当按下按钮 pbtn 时，我需要使用 storyboard API 将我的游戏从一个场景转换到另一个场景。以下是我的代码。

local storyboard = require "storyboard"
local scene = storyboard.newScene()

-- Forward References

local title

local centerX = display.contentCenterX
local centerY = display.contentCenterY
display.setStatusBar(display.HiddenStatusBar)

function anim_pbtn(event)
        transition.to(pbtn, {time = 500, alpha = 0, xScale = 2, yScale = .6})
        storyboard.gotoScene("game", "fade", 1000)
end

function scene:createScene(event)
    local screenGroup = self.view

    mbg = display.newImage("mbg.png")
        mbg.x = centerX
        mbg.y = centerY
        mbg.width = display.width
        mbg.height = display.height
    
    -- Add the following line to screenGroup
    screenGroup:insert(mbg)

    title = display.newImage("title.png")
        title.xScale = .7
        title.yScale = .7
        title.x = centerX
        
    -- Add the following line to screenGroup
    screenGroup:insert(title)

    pbtn = display.newImage("play_btn.png")
        pbtn.xScale = .7
        pbtn.yScale = .7
        pbtn.x = centerX
        pbtn.y = display.contentHeight - 210
    
    -- Add the following line to screenGroup
    screenGroup:insert(pbtn)

    ibtn = display.newImage("ins_btn.png")
        ibtn.xScale = .7
        ibtn.yScale = .7
        ibtn.x = centerX
        ibtn.y = display.contentHeight - 130
    
    -- Add the following line to screenGroup
    screenGroup:insert(ibtn)

    cbtn = display.newImage("cre_btn.png")
        cbtn.xScale = .7
        cbtn.yScale = .7
        cbtn.x = centerX
        cbtn.y = display.contentHeight - 50
    
    -- Add the following line to screenGroup
    screenGroup:insert(cbtn)
end

function scene:enterScene(event)
    pbtn:addEventListener("tap", anim_pbtn)
end

function scene:exitScene(event)

end

function scene:destroyScene(event)

end

scene:addEventListener("createScene", scene)
scene:addEventListener("enterScene", scene)
scene:addEventListener("exitScene", scene)
scene:addEventListener("destroyScene", scene)

return scene

只需要将这行代码添加到 screenGroup 中，才能进行过渡效果的实现。