scrollbar按钮拖拽时消失

[sharebophar]

-------------------------------------
-- (callback)
-- on bar move
-------------------------------------
function UIScrollBar:onBarMove(x, y, dx, dy)
    if not self.barDown then return end

    local bar = self.bar

    if self.dir == "vertical" then
        local after = bar:getY() + dy
        if after < 0 then
            after = 0
        elseif after + bar:getHeight() > self:getHeight() then
            after = self:getHeight() - bar:getHeight()
        end
-- 增加除数为0的判定
        local spaceHeight = self:getHeight() - bar:getHeight()
        if spaceHeight == 0 then spaceHeight = 1 end
        self.barPosRatio = after / spaceHeight
    else
        local after = bar:getX() + dx
        if after < 0 then
            after = 0
        elseif after + bar:getWidth() > self:getWidth() then
            after = self:getWidth() - bar:getWidth()
        end
-- 增加除数为0的判定
        local spaceWidth = self:getWidth() - bar:getWidth()
        if spaceWidth == 0 then spaceWidth = 1 end
        self.barPosRatio = after / spaceWidth
    end
    self:setBarPos(self.barPosRatio)
end