如何设置绘制线的最大长度？（Corona SDK）

Question

我目前正在研究一些项目，它包含一个要绘制的线的选项。但我通常不能设置最大行长。我怎样才能做到这一点？

这里是距离公式的代码（我认为）：

local function distanceBetween(e, prev) 
     local distanceBetween = 0 
    local dist_x = e.x - prevX ; local dist_y = e.y - prevY; 
    local distanceBetween = math.sqrt((dist_x*dist_x) + (dist_y*dist_y)) 
    return distanceBetween 
end 

这里是一行代码：

local lines = {} 
    local myLines = {}  
    local prevX,prevY 



    local i = 1 

    --prevX = x1, prevY = y1, e.x = x2, e.y = y2 

    local function drawLine(e) 
     distanceBetween = false 
     if(e.phase == "began") then 
     myLines[i] = {} 
     prevX = e.x 
     prevY = e.y 
      elseif(e.phase == "moved")then 
       if prevX then 
        myLines[i][#myLines[i] + 1] = display.newLine(prevX,prevY,e.x,e.y) 
        myLines[i][#myLines[i]]:setColor(255,255,0) 
        myLines[i][#myLines[i]].width = 5 
        myLines[i][#myLines[i]].alpha=1 
        myLines[i][#myLines[i]].myName = "Line" 
        dist_x = e.x - prevX 
        dist_y = e.y - prevY 
        physics.addBody(myLines[i][#myLines[i]], "static", { density = 1, friction = 0.5, bounce = 1.6, shape = {0, 0, dist_x, dist_y, 0, 0} }) 
        lineGroup:insert(myLines[i][#myLines[i]]) 



        distanceBetween = true 
         if (distanceBetween > 50) then 
         drawLine("ended") 
         end 
        end -- this is how i think line should be maximized 

        prevX = e.x 
        prevY = e.y 
      elseif(e.phase == "ended")then 
       prevX = nil 
       prevY = nil 
       i = i + 1 
       removeLine(myLines[#myLines-1]) 
      end 
     end 
     Runtime:addEventListener("touch",drawLine); 

Answer 1

编辑：这工作得很好，我电晕应用程序。这是你想要做的吗？

local physics = require "physics" 
physics.start() 

local lines = {} 
local lineGroup = display.newGroup() 
local prevX,prevY 
local isDrawing = false 
local i = 0 

local function distanceBetween(x1, y1, x2, y2) 
    local dist_x = x2 - x1 
    local dist_y = y2 - y1 
    local distanceBetween = math.sqrt((dist_x*dist_x) + (dist_y*dist_y)) 
    return distanceBetween 
end 

local function drawLine(e) 
    if(e.phase == "began") then 
     prevX = e.x 
     prevY = e.y 
     isDrawing = true 
     i = i + 1 
    elseif(e.phase == "moved") then 
     local distance = distanceBetween(prevX, prevY, e.x, e.y) 
     if(isDrawing and distance < 100) then 
      if(lines[i]) then lineGroup:remove(i) end 
      lines[i] = display.newLine(prevX, prevY, e.x, e.y) 
      lines[i]:setColor(255, 255, 0) 
      lines[i].width = 5 

      local dist_x = e.x - prevX 
      local dist_y = e.y - prevY 
      physics.addBody(lines[i], "static", { density = 1, friction = 0.5, bounce = 1.6, shape = {0, 0, dist_x, dist_y, 0, 0} }) 
      lineGroup:insert(lines[i]) 
     end 
    elseif(e.phase == "ended") then 
     isDrawing = false 
    end 
end 

Runtime:addEventListener("touch",drawLine)