[海报澄清后编辑]
此代码将绘制/继续一条折线到用户接下来单击的位置。
如果用户在他们开始的绿色圆圈中单击返回，则多段线将被填充。
这是代码和小提琴：http: //jsfiddle.net/m1erickson/qwd2a/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<!--[if lt IE 9]><script type="text/javascript" src="../excanvas.js"></script><![endif]-->
<style>
body{ background-color: ivory; padding:10px; }
canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var canvasMouseX;
var canvasMouseY;
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var storedLines=[];
var startX=0;
var startY=0;
var radius=7;
ctx.strokeStyle="orange";
ctx.font = '12px Arial';
$("#canvas").mousedown(function(e){handleMouseDown(e);});
function handleMouseDown(e){
canvasMouseX=parseInt(e.clientX-offsetX);
canvasMouseY=parseInt(e.clientY-offsetY);
// Put your mousedown stuff here
if(hitStartCircle(canvasMouseX, canvasMouseY)){
fillPolyline();
return;
}
storedLines.push({x:canvasMouseX,y:canvasMouseY});
if(storedLines.length==1){
startX=canvasMouseX;
startY=canvasMouseY;
ctx.fillStyle="green";
ctx.beginPath();
ctx.arc(canvasMouseX, canvasMouseY, radius, 0 , 2 * Math.PI, false);
ctx.fill();
}else{
var c=storedLines.length-2;
ctx.strokeStyle="orange";
ctx.lineWidth=3;
ctx.beginPath();
ctx.moveTo(storedLines[c].x,storedLines[c].y);
ctx.lineTo(canvasMouseX, canvasMouseY);
ctx.stroke();
}
}
function hitStartCircle(x,y){
var dx=x-startX;
var dy=y-startY;
return(dx*dx+dy*dy<radius*radius)
}
function fillPolyline(){
ctx.strokeStyle="red";
ctx.fillStyle="blue";
ctx.lineWidth=3;
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.beginPath();
ctx.moveTo(storedLines[0].x,storedLines[0].y);
for(var i=0;i<storedLines.length;i++){
ctx.lineTo(storedLines[i].x,storedLines[i].y);
}
ctx.closePath();
ctx.fill();
ctx.stroke();
storedLines=[];
}
$("#clear").click(function(){
ctx.clearRect(0,0,canvas.width,canvas.height);
storedLines=[];
});
}); // end $(function(){});
</script>
</head>
<body>
<p>Click to draw lines</p>
<p>Click back in the green circle to close+fill</p><br/>
<canvas id="canvas" width=300 height=300></canvas><br/>
<button id="clear">Clear Canvas</button>
</body>
</html>
[基于较少信息的上一个答案]
看起来您正在尝试：
- 让用户点击画布上的点。
- 在 storedLines[] 中收集这些点。
- 稍后，使用 storedLines[] 绘制线条 + 填充颜色。
- （我假设您不想在用户点击时立即绘制线条，因为您说“我需要检测绘制线条何时完成......”。）如果您确实想在用户点击时立即绘制，请给我一个发表评论，我也可以为您提供替代方案；）
如果我可以在您的代码中建议进行一些清理：
这是在画布上获取鼠标位置的好方法：
// before you begin listening for mouseclicks,
// get the canvas’ screen position into offsetX/offsetY
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
// then when a mousedown event occurs
// use e.clientX/Y (not e.pageX/Y) to get the mouse position on the canvas
canvasMouseX=parseInt(e.clientX-offsetX);
canvasMouseY=parseInt(e.clientY-offsetY);
当您实际使用上下文和存储线绘制路径时：
- 要关闭路径，请将 context.closePath() 放在 context.stroke() 和 context.fill() 之前。
- 设置一个填充样式和描边样式。
执行 context.fill() 和 context.stroke() -- 如果不使用 fill()，则不会获得颜色填充。
// close a path
context.closePath();
context.fillStyle=”blue”;
context.strokeStyle=”rgb(180,80,95)”;
context.fill();
context.stroke();
这是代码和小提琴：http: //jsfiddle.net/m1erickson/zYsQh/
<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<!--[if lt IE 9]><script type="text/javascript" src="../excanvas.js"></script><![endif]-->
<style>
body{ background-color: ivory; padding:10px; }
canvas{border:1px solid red;}
</style>
<script>
$(function(){
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var canvasMouseX;
var canvasMouseY;
var canvasOffset=$("#canvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var storedLines=[];
ctx.strokeStyle="orange";
ctx.font = '12px Arial';
$("#canvas").mousedown(function(e){handleMouseDown(e);});
function handleMouseDown(e){
canvasMouseX=parseInt(e.clientX-offsetX);
canvasMouseY=parseInt(e.clientY-offsetY);
// Put your mousedown stuff here
storedLines.push({x:canvasMouseX,y:canvasMouseY});
var count=storedLines.length;
var X=canvasMouseX-(count<10?4:7);
ctx.strokeStyle="orange";
ctx.fillStyle="black";
ctx.lineWidth=1;
ctx.beginPath();
ctx.arc(canvasMouseX, canvasMouseY, 8, 0 , 2 * Math.PI, false);
ctx.fillText(storedLines.length, X, canvasMouseY+4);
ctx.stroke();
}
$("#draw").click(function(){
ctx.strokeStyle="red";
ctx.fillStyle="blue";
ctx.lineWidth=3;
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.beginPath();
ctx.moveTo(storedLines[0].x,storedLines[0].y);
for(var i=0;i<storedLines.length;i++){
ctx.lineTo(storedLines[i].x,storedLines[i].y);
}
ctx.closePath();
ctx.fill();
ctx.stroke();
storedLines=[];
});
$("#clear").click(function(){
ctx.clearRect(0,0,canvas.width,canvas.height);
storedLines=[];
});
}); // end $(function(){});
</script>
</head>
<body>
<p>Click to create storedLines[]</p>
<p>Then press the Draw button to fill the path</p><br/>
<canvas id="canvas" width=300 height=300></canvas><br/>
<button id="clear">Clear Canvas</button>
<button id="draw">Draw</button>
</body>
</html>