长列表：滚动可视区的流畅刷新

-- 错误：千行建千节点，滚动全程高耗
for i = 1, #rows do
    createRowNode(i)
end

local ROW_H, POOL_N = 60, 12
local function onScroll(offset)
    local first = math.floor(offset / ROW_H) + 1
    for i = 1, POOL_N do
        local node = pool[i]
        local dataIdx = first + i - 1
        node:setPosition(0, -(dataIdx - 1) * ROW_H)
        fillRow(node, rows[dataIdx])
    end
end