LOVE2D中实现一个简单的摇杆

转自：http://blog.youkuaiyun.com/jkevin2016/article/details/52885137

local local_class = class() --这里用到云风的CLASS代码
local gr=love.graphics
local function getDistance (pointO,pointA )    

    distance = math.pow((pointO.x - pointA.x),2) + math.pow((pointO.y - pointA.y),2);    
    distance = math.sqrt(distance);    
    pointO,pointA=nil,nil
    return distance;    
end

function local_class:ctor(bg,spr)
    self.bg = bg
    self.spr = spr 
    self.dir = 0
    self.renge = 0
    self.power = 0
    self.w2 = self.bg:getWidth()/2
    self.point = {x=0,y=0}
    self.offset = {x=0,y=0}
    self.press = false
end

function local_class:update()

end

function local_class:setPoint(x,y)
    self.point.x ,self.point.y = x,y
end

function local_class:draw()
    gr.draw(bg,self.point.x,self.point.y,0,1,1,110,110)
    gr.draw(center,self.point.x+self.offset.x,self.point.y+self.offset.y,0,1,1,48,48)
end


function local_class:touchpressed( id, x, y, dx, dy, pressure )
    local radius  = self.w2
    local dis = getDistance({x=x,y=y},self.point);  
    if dis < radius then
        self.press = true
        self.offset.x =  (x-self.point.x)
        self.offset.y =  (y-self.point.y)
    end

end

function local_class:touchreleased( id, x, y, dx, dy, pressure )
    if self.press then 
        self.offset.x = 0
        self.offset.y =  0
    end
    self.press = false
    self.dir = 0
end

function local_class:touchmoved( id, x, y, dx, dy, pressure )
    if self.press then 
        local radius  = self.w2
        local dis = getDistance({x=x,y=y},self.point);  
        local angle = math.acos ( (x - self.point.x)/dis );

        if dis>radius then
            if ( y >  self.point.y ) then
                self.offset.x =  radius*math.cos(angle)
                self.offset.y = radius*math.sin(angle)
             else 
                self.offset.x = radius*math.cos(angle)
                self.offset.y =  -(radius*math.sin(angle))
            end

        else
            self.press = true
            self.offset.x =  (x-self.point.x)
            self.offset.y =  (y-self.point.y)
        end
        if dis > self.renge then 
            if (y > self.point.y) then
                self:__checkDirection(angle);  
            else  
                self:__checkDirection(-angle);  
            end
        else 
            self.dir = 0
        end 
        self.power = dis / radius
    end
end

function local_class:getDirection()
    return self.dir
end

function local_class:__checkDirection(angle)
    local dir = 0
    local M_PI=math.pi
    if (angle >= -M_PI/8.0 and angle <= M_PI/8.0)   then
        dir = 6;  
    end  

    --[[右边走 -八分之派 到 八分之派--]]  
    if (angle >= -(M_PI/8.0) and angle <= M_PI/8.0)   then
        dir = 6;  

    --[[右上方向 八分之派 到 八分之三派--]]  
    elseif( angle >= M_PI/8.0 and angle < 3*M_PI/8.0)   then
        dir = 3;  

    --[[上方向 八分之三派 到 八分之五派--]]  
    elseif( angle >= 3*M_PI/8.0 and angle <= 5*M_PI/8.0)   then
        dir = 2;  

    --[[左上方向 八分之5派 到 八分之七派--]]  
    elseif( angle > 5*M_PI/8.0 and angle < 7*M_PI/8.0)   then
        dir = 1;  

    --[[左方向--]]  
    elseif( (angle >= 7*M_PI/8.0 and angle <= M_PI) or (angle <= -7*M_PI/8.0 and angle >= -M_PI))  then
        dir = 4;  

    --[[左下方向--]]  
    elseif( angle > -7*M_PI/8.0 and angle < -5*M_PI/8.0)   then
        dir = 7;  

    --[[下方向--]]  
    elseif( angle >= -5*M_PI/8.0 and angle <= -3*M_PI/8.0)  then
        dir = 8;  

    --[[右下方向--]]  
    elseif( angle > -3*M_PI/8.0 and angle < -M_PI/8.0 ) then
        dir = 9;  
    end  

    self.dir = dir
end

return local_class

这里有个小例子
链接: http://pan.baidu.com/s/1boQcpVT 密码: drsm