如何使html中的canvas元素可点击？
Sha*_*ham 3 html javascript canvas
我正在设计一个有很多数学数字的网页.例如菱形,正方形,矩形,三角形......
我想要实现的是,当我点击任何一个数字时,它应该显示一个msg/info类的东西.
我只有一个画布ID,其中有很多数字,我如何使它们可点击以便我可以显示每个图形所需的信息
以下是如何使用原生html画布让用户收到有关他们点击的形状的消息:
- 对于每个形状,将它们的角点放在javascript对象中
- 将所有这些形状对象放在一个数组中
- 听mousedown事件
- 在mousedown中使用context.isPointInPath检查鼠标是否在每个形状内
- 如果鼠标位于对象内,则显示有关该形状的消息
演示:http: //jsfiddle.net/m1erickson/wPMk5/
示例代码:
<!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>
<style>
body{ background-color: ivory; }
#canvas{border:1px solid red;}
</style>
<script>
$(function(){
// canvas variables
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var $canvas=$("#canvas");
var canvasOffset=$canvas.offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var scrollX=$canvas.scrollLeft();
var scrollY=$canvas.scrollTop();
// set styles
ctx.fillStyle="skyblue";
ctx.strokeStyle="lightgray";
ctx.lineWidth=2;
// create a triangle and parallelogram object
var triangle={
points:[{x:25,y:100},{x:50,y:50},{x:75,y:100}],
message:"I am a triangle"
}
var parallelogram={
points:[{x:150,y:50},{x:250,y:50},{x:200,y:100},{x:100,y:100}],
message:"I am a parallelogram"
}
// save the triangle and parallelogram in a shapes[] array
var shapes=[];
shapes.push(triangle);
shapes.push(parallelogram);
// function to draw (but not fill/stroke) a shape
// (needed because isPointInPath only tests the last defined path)
function define(shape){
var points=shape.points;
ctx.beginPath();
ctx.moveTo(points[0].x,points[0].y);
for(var i=1;i<points.length;i++){
ctx.lineTo(points[i].x,points[i].y);
}
}
// function to display a shape on the canvas (define + fill + stroke)
function draw(shape){
define(shape);
ctx.fill();
ctx.stroke();
}
// display the triangle and parallelogram
draw(triangle);
draw(parallelogram);
// called when user clicks the mouse
function handleMouseDown(e){
e.preventDefault();
// get the mouse position
var mouseX=parseInt(e.clientX-offsetX);
var mouseY=parseInt(e.clientY-offsetY);
// iterate each shape in the shapes array
for(var i=0;i<shapes.length;i++){
var shape=shapes[i];
// define the current shape
define(shape);
// test if the mouse is in the current shape
if(ctx.isPointInPath(mouseX,mouseY)){
// if inside, display the shape's message
alert(shape.message);
}
}
}
// listen for mousedown events
$("#canvas").mousedown(function(e){handleMouseDown(e);});
}); // end $(function(){});
</script>
</head>
<body>
<canvas id="canvas" width=300 height=300></canvas>
</body>
</html>
如果您可以改用 SVG，则可以非常轻松地实现此目标。使用http://svg-edit.googlecode.com/svn/branches/2.5.1/editor/svg-editor.html你可以绘制相关的形状，你可以获得 svg 代码。向其添加 onclick() 事件。
通过这个在线工具，您可以创建形状
点击SVG获取代码
代码
<svg width="640" height="480" xmlns="http://www.w3.org/2000/svg">
<!-- Created with SVG-edit - http://svg-edit.googlecode.com/ -->
<g>
<title>Layer 1</title>
<rect id="svg_1" height="74" width="150" y="95" x="58" stroke-width="5" stroke="#000000" fill="#FF0000"/>
<ellipse ry="35" rx="42" id="svg_2" cy="216" cx="158" stroke-width="5" stroke="#000000" fill="#FF0000"/>
<ellipse ry="36" rx="80" id="svg_3" cy="123" cx="342" stroke-width="5" stroke="#000000" fill="#0000ff"/>
<path id="svg_4" d="m265,257l63,-59l82,47l-22,71l-84,5l-39,-64z" stroke-width="5" stroke="#000000" fill="#0000ff"/>
</g>
</svg>
您可以向 this.and 添加 onclick 事件。下面还显示了添加jquery 标题鼠标。
<rect id="svg_29" class="popup_tool" title="Message you want to popup when mouse over" height="17" width="20" y="224" x="452" stroke-linecap="null" stroke-linejoin="null" stroke-dasharray="null" stroke-width="3" stroke="#000000" fill="#ff0000"/>
希望你得到答案