滚动列表：只建可视区的格子复用

-- 错误：全量建节点，滚动全程高耗
for i = 1, #rows do
    createRowNode(i)
end

local view = TableViewEx.new({
    size = cc.size(560, 400),
    cellSizeForTable = function()
        return 560, 80
    end,
    tableCellAtIndex = function(view, idx)
        return buildRow(idx)
    end,
    numberOfCellsInTableView = function()
        return #rows
    end,
})