<html>
<head>
<title>canvas时钟</title>
</head>
<body>
<canvas id="canvas" width="200" height="200" style="border:1px solid #000;">您的浏览器不支持Canvas。</canvas>
<script type="text/javascript" language="javascript" charset="utf-8">
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
if(ctx){
var timerId;
var frameRate = 60;
function canvObject(){
this.x = 0;
this.y = 0;
this.rotation = 0;
this.borderWidth = 2;
this.borderColor = '#000000';
this.fill = false;
this.fillColor = '#ff0000';
this.update = function(){
if(!this.ctx)throw new Error('你没有指定ctx对象。');
var ctx = this.ctx
ctx.save();
ctx.lineWidth = this.borderWidth;
ctx.strokeStyle = this.borderColor;
ctx.fillStyle = this.fillColor;
ctx.translate(this.x, this.y);
if(this.rotation)ctx.rotate(this.rotation * Math.PI/180);
if(this.draw)this.draw(ctx);
if(this.fill)ctx.fill();
ctx.stroke();
ctx.restore();
}
};
function Line(){};
Line.prototype = new canvObject();
Line.prototype.fill = false;
Line.prototype.start = [0,0];
Line.prototype.end = [5,5];
Line.prototype.draw = function(ctx){
ctx.beginPath();
ctx.moveTo.apply(ctx,this.start);
ctx.lineTo.apply(ctx,this.end);
ctx.closePath();
};
function Circle(){};
Circle.prototype = new canvObject();
Circle.prototype.draw = function(ctx){
ctx.beginPath();
ctx.arc(0, 0, this.radius, 0, 2 * Math.PI, true);
ctx.closePath();
};
var circle = new Circle();
circle.ctx = ctx;
circle.x = 100;
circle.y = 100;
circle.radius = 90;
circle.fill = true;
circle.borderWidth = 6;
circle.fillColor = '#ffffff';
var hour = new Line();
hour.ctx = ctx;
hour.x = 100;
hour.y = 100;
hour.borderColor = "#000000";
hour.borderWidth = 10;
hour.rotation = 0;
hour.start = [0,20];
hour.end = [0,-50];
var minute = new Line();
minute.ctx = ctx;
minute.x = 100;
minute.y = 100;
minute.borderColor = "#333333";
minute.borderWidth = 7;
minute.rotation = 0;
minute.start = [0,20];
minute.end = [0,-70];
var seconds = new Line();
seconds.ctx = ctx;
seconds.x = 100;
seconds.y = 100;
seconds.borderColor = "#ff0000";
seconds.borderWidth = 4;
seconds.rotation = 0;
seconds.start = [0,20];
seconds.end = [0,-80];
var center = new Circle();
center.ctx = ctx;
center.x = 100;
center.y = 100;
center.radius = 5;
center.fill = true;
center.borderColor = 'orange';
for(var i=0,ls=[],cache;i<12;i++){
cache = ls[i] = new Line();
cache.ctx = ctx;
cache.x = 100;
cache.y = 100;
cache.borderColor = "orange";
cache.borderWidth = 2;
cache.rotation = i * 30;
cache.start = [0,-70];
cache.end = [0,-80];
}
timerId = setInterval(function(){
// 清除画布
ctx.clearRect(0,0,200,200);
// 填充背景色
ctx.fillStyle = 'orange';
ctx.fillRect(0,0,200,200);
// 表盘
circle.update();
// 刻度
for(var i=0;cache=ls[i++];)cache.update();
// 时针
hour.rotation = (new Date()).getHours() * 30;
hour.update();
// 分针
minute.rotation = (new Date()).getMinutes() * 6;
minute.update();
// 秒针
seconds.rotation = (new Date()).getSeconds() * 6;
seconds.update();
// 中心圆
center.update();
},(1000/frameRate)|0);
}else{
alert('您的浏览器不支持Canvas无法预览.\n跟我一起说："很遗憾!"');
}
</script>
</body>
</html>
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