canvas高级篇（转载）移动元素

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本文转载在http://bbs.blueidea.com/thread-2979405-1-1.html

哈哈哈，好骚气！终于解决了我的需求。可以移动canvas内的多个元素

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >

<head>

    <meta http-equiv="Content-Type" content="text/html; charset=gb2312" />

    <script type="text/javascript">

        var list=[];

        var currentC;

        var _e={};

        var cricle = function(x,y,r){

            this.x=x;

            this.y=y;

            this.r=r;

            this.isCurrent=false;

            this.drawC=function(ctx,x,y){

                ctx.save();

                ctx.beginPath();

                ctx.moveTo(this.x,this.y-this.r);

                ctx.arc(this.x,this.y,this.r,*Math.PI,,true);

                if ((x && y && ctx.isPointInPath(x, y) && !currentC )||this.isCurrent) {

                    ctx.fillStyle = '#ff0000';

                    currentC=this;

                    this.isCurrent=true;

                }else{

                    ctx.fillStyle = '#999999';

                }

                ctx.fill();

            }

        }

        function draw(){

            var canvas = document.getElementById('tutorial');

            if (canvas.getContext){

                var ctx = canvas.getContext('2d');

                for(var i=;i<;i++){

                    var c=new cricle(*i,*i,*i);

                    c.drawC(ctx);

                    list.push(c);

                }

            }

        }

        function reDraw(e){

            e=e||event;

            var canvas = document.getElementById('tutorial');

            var x = e.clientX - canvas.offsetLeft;

            var y = e.clientY - canvas.offsetTop;

            canvas.width = canvas.width;

            if (canvas.getContext){

                var ctx = canvas.getContext('2d');

                for(var i=;i<list.length;i++){

                    var c=list[i];

                    c.drawC(ctx,x,y);

                }

            }

        }

        function show(e){

            e=e||event;

            var canvas = document.getElementById('tutorial');

            var ctx = canvas.getContext('2d');

            var x = e.clientX - canvas.offsetLeft;

            var y = e.clientY - canvas.offsetTop;

            if(currentC){

                currentC.x=parseInt(x+(x-currentC.x)/);

                currentC.y=parseInt(y+(y-currentC.y)/);

            }

            _e=e;

        }

        window.onload=function(){

            var canvas = document.getElementById('tutorial');

            draw();

            canvas.onmousedown=function(e){

                e=e||event;

                var x = e.clientX - canvas.offsetLeft;

                var y = e.clientY - canvas.offsetTop;

                if(currentC)

                    currentC.isCurrent=false;

                currentC=null;

                reDraw(e);

                _e=e;

                var showTimer=setInterval(function(e){

                    reDraw(e);

                },,_e);

                canvas.onmousemove=show;

                document.onmouseup=function(){

                    if(currentC)

                        currentC.isCurrent=false;

                    currentC=null;

                    canvas.onmousemove=null;

                    clearInterval(showTimer);

                }

            }

        }

    </script>

    <style type="text/css">

        canvas { border: 1px solid black; }

    </style>

</head>

<body style="background:#eeeeee;">

<div style="background:#0f0;width:100px;height:100px;position:absolute;left:100px;top:100px;z-index:1;" onclick="alert(1);"></div>

<canvas id="tutorial" width="" height="" style="z-index:100;display:block;position:absolute;"></canvas>

</body>

<script>

</script>

</html>