In Corona SDK, how do I limit the number of lines

问题:

If I move the mouse off the line path when drawing a line, new lines continue appearing from the same center point. I have been trying to limit it to one line only, but I've not had much success. This is my code so far:

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
        lineGroup:removeSelf()
        lineGroup = nil
        lineGroup = display.newGroup()
        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]:setStrokeColor( 0,0,1 )
            lines[i].strokeWidth = 5

            local dist_x = e.x - prevX
            local dist_y = e.y - prevY
            physics.addBody(lines[i], "static", { density = 1, friction = .6, bounce = 2, 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)

If anyone could help, that would be great.

回答1:

as I understood what you want is something like this?

local physics = require("physics");

local lineGroup = display.newGroup()

local currentLine = nil;

local prevX,prevY


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 redrawLine(x1, y1, x2, y2)
    if (currentLine) then
        currentLine:removeSelf();
    end

    currentLine = display.newLine(x1, y1, x2, y2);
    currentLine:setStrokeColor(0,0,1);
    currentLine.strokeWidth = 5;
end

local function drawLine(e)
    if(e.phase == "began") then

        prevX = e.x
        prevY = e.y

        if (currentLine) then
            currentLine:removeSelf();
            currentLine = nil;
        end

    elseif(e.phase == "moved") then
        local distance = distanceBetween(prevX, prevY, e.x, e.y)
        if(distance < 100) then 
            redrawLine(prevX, prevY, e.x, e.y);
        end
    elseif(e.phase == "ended") then

        if (currentLine) then
            local dist_x = e.x - prevX
            local dist_y = e.y - prevY
            physics.addBody(currentLine, "static", { density = 1, friction = .6, bounce = 2, shape = {0, 0, dist_x, dist_y, 0, 0} } )
            lineGroup:insert(currentLine);
        end
    end
end

Runtime:addEventListener("touch",drawLine)

Enjoy!

Edited: code.