android - 错误：尝试将全局对象索引为零值：corona SDK

Question

我收到错误：

运行时错误 ...n-stylr\documents\corona projects\happy_day\game.lau:50: 尝试索引全局“city1”（零值）

我的代码如下：

function scene:createScene(event)

local screenGroup = self.view

local background = display.newImage("background1.jpg")

local city1 = display.newImage("bild.png")
city1:setReferencePoint(display.BottomLeftReferencePoint)
city1.x = 0
city1.y = 640
city1.speed = 1

local city2 = display.newImage("bild.png")
city2:setReferencePoint(display.BottomLeftReferencePoint)
city2.x = 1136
city2.y = 640
city2.speed = 1

local city3 = display.newImage("build2.png")
city3:setReferencePoint(display.BottomLeftReferencePoint)
city3.x = 0
city3.y = 640
city3.speed = 2

local city4 = display.newImage("build2.png")
city4:setReferencePoint(display.BottomLeftReferencePoint)
city4.x = 1136
city4.y = 640
city4.speed = 2
end

function scene:enterScene(event)

Runtime:addEventListener("touch", touchScreen)
print(city1)
city1.enterFrame = scrollCity
Runtime:addEventListener("enterFrame", city1)

city2.enterFrame = scrollCity
Runtime:addEventListener("enterFrame", city2)

city3.enterFrame = scrollCity
Runtime:addEventListener("enterFrame", city3)

city4.enterFrame = scrollCity
Runtime:addEventListener("enterFrame", city4)

end

Answer 1

只需local city1在函数外部声明createScene并创建city1为：

local city1;

function scene:createScene(event)
   -- your code for localGroup and bg 

   city1 = display.newImage("bild.png")  -- just create city1 as this

   -- do the rest of your code
end

如果在引用其他城市（city2 ,3 或 4）时发生错误，请对所有这些城市执行相同的方法。

继续编码...... :)