HTML5编程实战之一：HTML5时钟
本文主要用到的知识
1、Canvas
2、三角函数
3、JavaScript
以上知识学习资源推荐
Canvas：https://developer.mozilla.org/en/Canvas_tutorial、http://www.w3.org/TR/2dcontext/
三角函数：http://zh.wikipedia.org/zh/%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0
JavaScript：https://developer.mozilla.org/en/JavaScript、http://www.w3school.com.cn/js/index.asp
源代码
<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title>超酷HTML5时钟(作者：http://www.cnblogs.com/jscode/)</title> <style type="text/css"> .time { text-align: center; width:400px; font-family: "Book Antiqua",Palatino,serif; font-size: 40px; font-weight: bold; text-shadow: 1px 1px 3px #333; position:absolute; } .time em { background: white; position: absolute; top: 5px; left: 130px; height: 18px; width: 140px; opacity: 0.4; } </style> <script type="text/javascript"> var canvas, context; function DrawClock() { canvas = document.getElementById("canvas"); context = canvas.getContext("2d"); setInterval("drawbackground()", 1000); } function drawbackground() { var radius = Math.min(canvas.width / 2, canvas.height / 2) - 15; var centerx = canvas.width / 2; var centery = canvas.height / 2; context.clearRect(0, 0, canvas.width, canvas.height); context.save(); context.lineWidth = 15; context.fillStyle = "#EFEFEF"; context.strokeStyle = "#000"; context.beginPath(); context.arc(centerx, centery, radius, 0, Math.PI * 2, 0); context.fill(); context.stroke(); context.closePath(); context.restore(); for (var i = 0; i < 60; i++) { context.save(); context.fillStyle = "#EFEFEF"; context.strokeStyle = "#000"; if (i % 5 == 0) { context.lineWidth = 3; } context.beginPath(); context.moveTo(centerx, centery); context.lineTo(centerx + (radius-6) * Math.cos(i * 6 * Math.PI / 180), centery - (radius-5) * Math.sin(i * 6 * Math.PI / 180)); context.fill(); context.stroke(); context.closePath(); context.restore(); } context.moveTo(centerx, centery); context.save(); context.fillStyle = "#EFEFEF"; context.strokeStyle = "#EFEFEF"; context.beginPath(); context.arc(centerx, centery, radius-15, 0, Math.PI * 2, 0); context.fill(); context.stroke(); context.closePath(); context.restore(); var r = radius - 25; context.font = "bold 20px 宋体"; Drawtext("1", centerx + (Math.cos(60 * Math.PI / 180) * r), centery - (Math.sin(60 * Math.PI / 180) * r)); Drawtext("2", centerx + (Math.cos(30 * Math.PI / 180) * r), centery - (Math.sin(30 * Math.PI / 180) * r)); Drawtext("3", centerx + (Math.cos(0 * Math.PI / 180) * r), centery - (Math.sin(0 * Math.PI / 180) * r)); Drawtext("4", centerx + (Math.cos(330 * Math.PI / 180) * r), centery - (Math.sin(330 * Math.PI / 180) * r)); Drawtext("5", centerx + (Math.cos(300 * Math.PI / 180) * r), centery - (Math.sin(300 * Math.PI / 180) * r)); Drawtext("6", centerx + (Math.cos(270 * Math.PI / 180) * r), centery - (Math.sin(270 * Math.PI / 180) * r)); Drawtext("7", centerx + (Math.cos(240 * Math.PI / 180) * r), centery - (Math.sin(240 * Math.PI / 180) * r)); Drawtext("8", centerx + (Math.cos(210 * Math.PI / 180) * r), centery - (Math.sin(210 * Math.PI / 180) * r)); Drawtext("9", centerx + (Math.cos(180 * Math.PI / 180) * r), centery - (Math.sin(180 * Math.PI / 180) * r)); Drawtext("10", centerx + (Math.cos(150 * Math.PI / 180) * r), centery - (Math.sin(150 * Math.PI / 180) * r)); Drawtext("11", centerx + (Math.cos(120 * Math.PI / 180) * r), centery - (Math.sin(120 * Math.PI / 180) * r)); Drawtext("12", centerx + (Math.cos(90 * Math.PI / 180) * r), centery - (Math.sin(90 * Math.PI / 180) * r)); context.save(); context.fillStyle="black"; context.beginPath(); context.arc(centerx,centery,10,0,Math.PI*2,0); context.fill(); context.stroke(); context.closePath(); context.restore(); drawpoint(centerx, centery, radius); } function drawpoint(centerx, centery, radius) { var date = new Date(); var h = date.getHours(); h = h < 13 ? h : h - 12; var m = date.getMinutes(); var s = date.getSeconds(); var th = date.getHours() < 10 ? "0" + date.getHours() : date.getHours(); var tm = m < 10 ? "0" + m : m; var ts = s < 10 ? "0" + s : s; document.getElementById("currtime").innerHTML = th + ":" + tm + ":" + ts; var hr = h * 30 * Math.PI / 180 + (m / 60) * 30 * Math.PI / 180 + 90 * Math.PI / 180; var mr = m * 6 * Math.PI / 180 + s / 60 * 6 * Math.PI / 180 + 90 * Math.PI / 180; var sr = s * 6 * Math.PI / 180 + 90 * Math.PI / 180; context.save(); context.lineWidth = 5; context.fillStyle = "darkgray"; context.strokeStyle = "black"; context.beginPath(); context.moveTo(centerx + 20 * Math.cos(hr), centery + 20 * Math.sin(hr)); context.lineTo(centerx - (radius - 120) * Math.cos(hr), centery - (radius - 120) * Math.sin(hr)); context.moveTo(centerx + 20 * Math.cos(mr), centery + 20 * Math.sin(mr)); context.lineTo(centerx - (radius - 80) * Math.cos(mr), centery - (radius - 80) * Math.sin(mr)); context.moveTo(centerx + 20 * Math.cos(sr), centery + 20 * Math.sin(sr)); context.lineTo(centerx - (radius - 50) * Math.cos(sr), centery - (radius - 50) * Math.sin(sr)); context.closePath(); context.fill(); context.stroke(); context.restore(); } function Drawtext(text, x, y) { context.save(); x -= (context.measureText(text).width / 2); y += 9; context.beginPath(); context.translate(x, y); context.fillText(text, 0, 0); context.restore(); } window.onload = DrawClock; </script> </head> <body> <h1>超酷HTML5时钟(作者：http://www.cnblogs.com/jscode/)</h1> <canvas id="canvas" width="400px" height="400px"></canvas> <div class="time"><span id="currtime">00:00:00</span><em></em></div> </body> </html>
方法作用解释：
DrawClock方法取得Canvas上下文
drawbackground 方法主要是画时钟的背景部分：边框、文字、刻度线
drawpoint 方法用来画时、分、秒线
Drawtext 方法是添加文字的
大家如果对代码有什么疑问可以留言，我尽量回复
