Action script 3 drawing app undo and redo function

问题

Can anyone show me how can I make undo and redo function? so this is my current action script. I cant figure how to do it and i see some example in some web site, the action script is to long to under stand. Pls show a simple way that i can make this work..

sorry for bad grammar...

import flash.display.MovieClip;
import flash.events.MouseEvent;

var pen_mc:MovieClip;
var drawing:Boolean = false;
var penSize:uint = 1;
var penColor:Number = 0x000000;

var shapes:Vector.<Shape>=new Vector.<Shape>(); 
var position:int=0;
const MAX_UNDO:int=10;


function init():void{

pen_mc = new MovieClip();
stage.addEventListener(MouseEvent.MOUSE_DOWN, startDrawing);
stage.addEventListener(MouseEvent.MOUSE_MOVE, isDrawing);
stage.addEventListener(MouseEvent.MOUSE_UP, finishedDrawing);
addChild(pen_mc);

}

init();

function startDrawing(e:MouseEvent):void{

trace("Pen Has started drawing");

drawing = true;
pen_mc.graphics.lineStyle(penSize, penColor);
pen_mc.graphics.moveTo(mouseX, mouseY);


}

function isDrawing(e:MouseEvent):void{
if(drawing){

    pen_mc.graphics.lineTo(mouseX, mouseY);
}

}


function finishedDrawing(e:MouseEvent):void{

     trace("finished drawing");
     drawing = false;

     var sh:Shape=new Shape();
     sh.graphics.copyFrom(pen_mc.graphics); // put current state into the vector
     shapes.push(sh);
     if (shapes.length>MAX_UNDO) shapes.unshift(); // drop oldest state
     position=shapes.indexOf(sh);
}
function undo():void {
    if (position>0) {
        position--;
        pen_mc.graphics.copyFrom(shapes[position].graphics);
    } // else can't undo
}
function redo():void {
    if (position+1<shapes.length) {
        position++;
        pen_mc.graphics.copyFrom(shapes[position].graphics);
    } // else can't redo
}


 function btn_undo(e:MouseEvent):void
        {
            undo();
        }

 function btn_redo(e:MouseEvent):void
        {
            redo();
        }

undo_btn.addEventListener(MouseEvent.CLICK, btn_undo);
redo_btn.addEventListener(MouseEvent.CLICK, btn_redo);

回答1:

You can use copyFrom() in Shape.graphics to store current condition, and the same to "redo", as your canvas is a Shape.

var shapes:Vector.<Shape>=new Vector.<Shape>(); 
var position:int=0;
const MAX_UNDO:int=10;
...
function finishedDrawing(e:MouseEvent):void{

     trace("finished drawing");
     drawing = false;

     var sh:Shape=new Shape();
     sh.graphics.copyFrom(penMC.graphics); // put current state into the vector
     shapes.push(sh);
     if (shapes.length>MAX_UNDO) shapes.unshift(); // drop oldest state
     position=shapes.indexOf(sh);
}
function undo():void {
    if (position>0) {
        position--;
        penMC.graphics.copyFrom(shapes[position].graphics);
    } // else can't undo
}
function redo():void {
    if (position+1<shapes.length) {
        position++;
        penMC.graphics.copyFrom(shapes[position].graphics);
    } // else can't redo
}

This approach lacks some features, as to drop part of undo/redo stack if first undone to a certain point, then drawn. You can try adding this function yourself.

来源：https://stackoverflow.com/questions/14828613/action-script-3-drawing-app-undo-and-redo-function

标签

actionscript-3

flash

drawing

undo

redo