装载完成：任务计数的完成判定

-- 错误：只靠末尾任务触发，失败即卡
function runTasks(tasks)
    for i, t in ipairs(tasks) do
        if i == #tasks then
            t(function() onAllLoaded() end)
        else
            t()
        end
    end
end

local total, done = 0, 0
local function addTask(fn)
    total = total + 1
    after(0, function()
        fn()
        done = done + 1
        if done >= total then
            onAllLoaded()
        end
    end)
end