我编写代码但未运行。 我有2个标签画布。当我改变帆布< 100的属性高度,然后箭头隐藏。如果我在标记画布之前没有写tag div,那么它运行正常。谢谢你的支持!!!! 的源代码:画布中的错误绘图箭头
<body>
<div id="yendau">LOL</div>
<canvas id="c" width="500" height="100">Brower of you doesn't not support Canvas</canvas>
<div>Yolooooooooooo</div>
<canvas id="d" width="500" height="300">Brower of you doesn't not support Canvas</canvas>
<script src="jquery-1.9.1.js"></script>
<script langauage="javascript">
function canvas_arrow(context, fromx, fromy, tox, toy){
var headlen = 20; // length of head in pixels
var dx = tox-fromx;
var dy = toy-fromy;
var angle = Math.atan2(dy,dx);
context.moveTo(fromx, fromy);
context.lineTo(tox, toy);
context.lineWidth=2;
context.moveTo(tox, toy);
context.lineTo(tox-headlen*Math.cos(angle+Math.PI/6),toy-headlen*Math.sin(angle+Math.PI/6));
context.moveTo(tox, toy);
context.lineTo(tox-headlen*Math.cos(angle-Math.PI/6),toy-headlen*Math.sin(angle-Math.PI/6));
}
$('document').ready(function(){
var count= parseInt($("canvas").length);
for(var i=0; i< count; i++){
var ctx= $("canvas")[i].getContext('2d');
ctx.beginPath();
//var x= $('#c').offset().left-15;
//var y= $('#c').offset().top-15;
var x= $('#'+$("canvas")[i].id).offset().left;
var y= $('#'+$("canvas")[i].id).offset().top+15;
var x1= x+100;
canvas_arrow(ctx,x,y,x1,y);
ctx.stroke();
}
});
第一件事是:总是用beginPath启动一个新路径 – GameAlchemist 2015-02-23 17:47:23