Question

我一直在谷歌搜索这个错误的废话（尝试索引全局＆＃39; square＆＃39;（零值）），但我似乎无法理解问题是什么......我知道它应该很容易修复，但我无法弄清楚我的生活。错误发生在最底层，我标记了问题。

enter code here
local backdrop = display.setDefault("background", 1, 1, 1)

local physics = require("physics")
physics.start()

_W = display.contentWidth; -- Get the width of the screen
_H = display.contentHeight; -- Get the height of the screen

motionDown = 0;
motionUp = 0;
motionRight = 0;
motionLeft = 0;
motionSquare = 5

speed = 4

local left = display.newRect(0,0,_W/2,_H/1.19)
    left.x = _W/4.5; left.y = _H/2;

local right = display.newRect(0,0,_W/2,_H/1.19)
    right.x = _W/1.25; right.y = _H/2;

local top = display.newRect(0,0,_W,_H/5.5)
    top.x = _W/2; top.y =0;

local bottem = display.newRect(0,0,_W,_H/5.5)
    bottem.x = _W/2; bottem.y =_H;

    player = display.newImage("player.png", display.contentCenterX, display.contentCenterY)
        player.x = math.random(10,_W-10)
        player.y = math.random(10,_H-10)

player:toFront(player)

physics.addBody( player, "static" )


function left:tap()
        motionDown = 0;
        motionUp = 0;
        motionRight = 0;
    motionLeft = -speed;

    local square = display.newRect( 0, 0, 5, 5 )
    square.strokeWidth = 3
    square:setFillColor( 0 )
    square:setStrokeColor( 0, 0, 0 )
    square.x = player.x + 10 ; square.y = player.y;

    local function moveSquare (event)
        square.x = square.x + motionSquare;
        end
        Runtime:addEventListener("enterFrame", moveSquare)



end
    left:addEventListener("tap",left)

function right:tap()
        motionDown = 0;
        motionUp = 0;
        motionLeft = 0;
    motionRight = speed;

        local square = display.newRect( 0, 0, 5, 5 )
        square.strokeWidth = 3
        square:setFillColor( 0 )
        square:setStrokeColor( 0, 0, 0 )
        square.x = player.x - 10 ; square.y = player.y;

        local function moveSquare (event)
            square.x = square.x - motionSquare;
            end
            Runtime:addEventListener("enterFrame", moveSquare)

end
    right:addEventListener("tap",right)

function top:tap()
        motionDown = 0;
        motionRight = 0;
        motionLeft = 0;
        motionUp = -speed;
        local left = display.newRect(0,0,5,5)

        local square = display.newRect( 0, 0, 5, 5 )
        square.strokeWidth = 3
        square:setFillColor( 0 )
        square:setStrokeColor( 0, 0, 0 )
        square.x = player.x ; square.y = player.y + 10;

        local function moveSquare (event)
            square.y = square.y + motionSquare;
            end
            Runtime:addEventListener("enterFrame", moveSquare)

end
    top:addEventListener("tap",top) 

function bottem:tap(event)
        motionRight = 0;
        motionUp = 0;
        motionLeft = 0;
    motionDown = speed;

        local square = display.newRect( 0, 0, 5, 5 )
        square.strokeWidth = 3
        square:setFillColor( 0 )
        square:setStrokeColor( 0, 0, 0 )
        square.x = player.x ; square.y = player.y - 10;

        local function moveSquare (event)
        square.y = square.y - motionSquare;
        end
        Runtime:addEventListener("enterFrame", moveSquare)


end

    bottem:addEventListener("tap",bottem)

- 我们的球员还没动。我们已经设置了听众来向左或向右移动角色，但现在我们实际上必须让他移动。我们使用运行时事件监听器来执行此操作，该监听器将沿x轴移动人员。

- 移动角色本地函数movePlayer（事件） player.x = player.x + motionRight; 如果是player.x＆gt; display.contentWidth然后player.x = 0 结束结束运行时：addEventListener（＆＃34; enterFrame＆＃34;，movePlayer）

local function movePlayer (event)
    player.x = player.x + motionLeft;
        if player.x < 0 then player.x = display.contentWidth
        end
    end
    Runtime:addEventListener("enterFrame", movePlayer)

local function movePlayer (event)
    player.y = player.y + motionUp;
        if player.y > display.contentHeight then player.y = 0
        end
    end
    Runtime:addEventListener("enterFrame", movePlayer)

local function movePlayer (event)
    player.y = player.y + motionDown;
        if player.y < 0 then player.y = display.contentHeight
        end
    end
    Runtime:addEventListener("enterFrame", movePlayer)

    if square.y > display.contentHeight then square.y = 0 ### This is the 
                                                                error
       end

Answer 1

这是范围相关的问题。与全局变量不同，局部变量的范围仅限于声明它们的块。因此，您的square变量只能在以下四个函数中访问：bottem，top，left和right。

简单的解决方案需要使用前向声明：

-- Top of file
local square 
-- Later in the code you use only name of variable without local key word

了解更多：

Scope for Beginners，
Faster Lua Code Using Forward Declarations in Corona SDK（youtube video），
Forward Declarations。

错误：尝试索引全球＆＃39; square＆＃39; （零值）

1 个答案: