在云朵前面的冠状病毒图像？

由于某种原因，我无法让 local helicopter = display.newImage("helicopter.png") 在云（移动背景）前显示，有没有好的解决方法？

<code>
function initcloud()
    local cloud1 = {}
    cloud1.imgpath = "cloud1.png"; --为云设置图像路径
    cloud1.movementSpeed = 10000; --确定云的移动速度
    table.insert(cloudTable, cloud1); --将云插入云表中

    local cloud2 = {}
    cloud2.imgpath = "cloud2.png";
    cloud2.movementSpeed = 12000;
    table.insert(cloudTable, cloud2);

    local cloud3 = {}
    cloud3.imgpath = "cloud3.png";
    cloud3.movementSpeed = 14000;
    table.insert(cloudTable, cloud3);
end -- END initcloud()

function getRandomcloud()
local temp = cloudTable[math.random(1, #cloudTable)] --从云表中获取随机云
local randomcloud = display.newImage(temp.imgpath); --physics.addBody(randomcloud, {isSensor = true});
randomcloud.myName = "cloud";
randomcloud.movementSpeed = temp.movementSpeed; --设置云的运动速度
randomcloud.x = math.random(10, _W);
randomcloud.y = -35;
randomcloud.rotation = math.random(0, 20); --移动云
cloudMove = transition.to(randomcloud, {
time = randomcloud.movementSpeed,
y = 500,
onComplete = function(self)
self.parent:remove(self);
self = nil;
end
});
end

function cloudtGame()
    cloudTimer1 = timer.performWithDelay(1400,getRandomcloud, 0)
    cloudTimer2 = timer.performWithDelay(2000,getRandomcloud, 0)
    cloudTimer3 = timer.performWithDelay(2400,getRandomcloud, 0)
end -- END cloudtGame()

initcloud()
cloudtGame()

local helicopter = display.newImage("helicopter.png")
</code>