JoyRocker(虚拟摇杆)的quick实现

需要实现的功能：
- 处理触屏事件，生成移动数据

--JoyRocker.lua
--[[ 虚拟摇杆： 通过触屏事件传出数据 ]]

local JoyRocker = class("JoyRocker",function ()
    -- body
    return display.newLayer()
end)

function JoyRocker:ctor()
    -- body
    self.rocker_radius = 50.0
    self.rodker_vec = cc.p(0,0)
    self:initUI()
    self:initTouch()
    print(self.rocker_vec)
end
--初始化点击事件
function JoyRocker:initTouch()
    -- body
    self:setTouchEnabled(true)
    self:addNodeEventListener(cc.NODE_TOUCH_EVENT,function(event)

        --printf("touch:%s Pos:(%0.2f,%0.2f)",event.name,event.x,event.y)
        if event.name == "began" then
            --todo
            self:touchBegan(event)
            return true
        elseif event.name == "moved" then
            --todo
            self:touchMoved(event)
        elseif event.name == "ended" then
            --todo
            self:touchEnded(event)
        end

    end)
end

function JoyRocker:initUI()
    -- body
    self.rockerBg = display.newSprite("joy_rocker_bg.png"):align(display.CENTER,display.cx,display.cy):addTo(self)
    self.rocker = display.newSprite("joy_rocker.png"):align(display.CENTER,display.cy):addTo(self)
    self:hideRocker()
end
--[[ 点击事件的回调函数 ]]
function JoyRocker:touchBegan(event)
    -- body
    --print("touch began")
    self:showRocker(event.x,event.y)
end

function JoyRocker:touchMoved( event )
    -- body
    --print("touch moved")
    self:refreshRocker(event.x,event.y)
end

function JoyRocker:touchEnded( event )
    -- body
    --print("touch ended")
    self:hideRocker()
end

--[[ 显示摇杆 ]]
function JoyRocker:showRocker(x,y)
    -- body
    self.rockerBg:setVisible(true)
    self.rocker:setVisible(true)
    self.rockerBg:setPosition(x,y)
    self.rocker:setPosition(x,y)
end
--[[ 隐藏摇杆 ]]
function JoyRocker:hideRocker()
    -- body
    self.rockerBg:setVisible(false)
    self.rocker:setVisible(false)
    self.rockerBg:setPosition(display.cx,display.cy)
    self.rocker:setPosition(display.cx,display.cy)
end

function JoyRocker:refreshRocker(x,y)
    -- body
    local bg_x = self.rockerBg:getPositionX()
    local bg_y = self.rockerBg:getPositionY()
    if cc.pGetDistance(cc.p(bg_x,bg_y),cc.p(x,y)) <= self.rocker_radius then
        --todo
        self.rocker:setPosition(x,y)
    else
        --todo
        local dis = cc.pGetDistance(cc.p(bg_x,y))
        local a = self.rocker_radius
        local b = dis - a
        local c = math.abs(y - bg_y)
        local d = a * c /(a + b)
        local e = math.sqrt(a^2-d^2)
        local aim_x = 0.0
        local aim_y = 0.0
        if bg_x == x or bg_y == y then
            --todo
            if bg_x == x then
                --todo
                aim_x = bg_x
                aim_y = y > bg_y and bg_y + self.rocker_radius or bg_y - self.rocker_radius
            elseif bg_y == y then
                --todo
                aim_x = x > bg_x and bg_x + self.rocker_radius or bg_x - self.rocker_radius
                aim_y = bg_y
            end
        else
            --todo
            if x > bg_x and y > bg_y then
                --第一象限
                aim_x = bg_x + e
                aim_y = bg_y + d
            elseif x < bg_x and y > bg_y then
                --第二象限
                aim_x = bg_x - e
                aim_y = bg_y + d
            elseif x < bg_x and y < bg_y then
                --第三象限
                aim_x = bg_x - e
                aim_y = bg_y - d
            elseif x > bg_x and y < bg_y then
                --第四象限
                aim_x = bg_x + e
                aim_y = bg_y - d
            end
        end
        self.rocker:setPosition(aim_x,aim_y)
    end
end

return JoyRocker

使用：

JoyRocker:new():align(display.CENTER,display.cy):addTo(self)