love2d 代码中的左滑不响应

function updateControl(c)

    c.x2, c.y2 = love.mouse.getPosition()

    if love.mouse.isDown(1) and c.isDown == 0 then

        c.x1, c.y1 = love.mouse.getPosition()
        c.isDown = 1

    elseif c.isDown == 1 and getDistance(c.x1, c.y1, c.x2, c.y2) > 2 then

        c.isDown = 2
        local angle = math.floor((getAngle(c.x1, c.y1, c.x2, c.y2) - 45) / 90) * 90

        if angle == 0 then c.up = true
        elseif angle == 90 then c.right = true
        elseif angle == 180 then c.down = true
        elseif angle == 270 then c.left = true
        end

    elseif c.isDown == 1 and not love.mouse.isDown(1) then

        c.isDown = 0
        c.tap = true

    elseif c.isDown == 2 and not love.mouse.isDown(1) then

        c.isDown = 0
    end

    return c
end

function getDistance(x1, y1, x2, y2)

    return math.sqrt((x2 - x1) ^ 2 + (y2 - y1) ^ 2)
end

function getAngle(x1, y1, x2, y2)

    return math.deg(math.atan2(y2 - y1, x2 - x1)) + 180
end

我正在使用love2d游戏框架制作游戏，游戏在鼠标上运行得很好，但是在实际手机上测试时，左滑不响应。请问有人能看出问题吗？（该框架使用lua语言）