之前学习了下html5中的canvas元素，为了练练手就实现了一个简易的时钟。时钟本身并不复杂，也没有使用图片进行美化，不过麻雀虽小五脏俱全，下面就与大家分享一下：
实现效果：
html代码：
- <!DOCTYPE html>
- <html>
- <head>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
- <title>Clock</title>
- <style type="text/css">
- *{
- margin: 0;
- padding: 0;
- }
- .canvas{
- margin-left: 20px;
- margin-top: 20px;
- border: solid 1px;
- }
- </style>
- </head>
- <body onload= "main()">
- <canvas class = "canvas" id="canvasId" width = '500px' height = '400px'></canvas>
- <script type= "text/javascript" src = "Clock.js"></script>
- </body>
- </html>
JS代码:
- var Canvas = {};
- Canvas.cxt = document.getElementById('canvasId').getContext('2d');
- Canvas.Point = function(x, y){
- this.x = x;
- this.y = y;
- };
- /*擦除canvas上的所有图形*/
- Canvas.clearCxt = function(){
- var me = this;
- var canvas = me.cxt.canvas;
- me.cxt.clearRect(0,0, canvas.offsetWidth, canvas.offsetHeight);
- };
- /*时钟*/
- Canvas.Clock = function(){
- var me = Canvas,
- c = me.cxt,
- radius = 150, /*半径*/
- scale = 20, /*刻度长度*/
- minangle = (1/30)*Math.PI, /*一分钟的弧度*/
- hourangle = (1/6)*Math.PI, /*一小时的弧度*/
- hourHandLength = radius/2, /*时针长度*/
- minHandLength = radius/3*2, /*分针长度*/
- secHandLength = radius/10*9, /*秒针长度*/
- center = new me.Point(c.canvas.width/2, c.canvas.height/2); /*圆心*/
- /*绘制圆心（表盘中心）*/
- function drawCenter(){
- c.save();
- c.translate(center.x, center.y);
- c.fillStyle = 'black';
- c.beginPath();
- c.arc(0, 0, radius/20, 0, 2*Math.PI);
- c.closePath();
- c.fill();
- c.stroke();
- c.restore();
- };
- /*通过坐标变换绘制表盘*/
- function drawBackGround(){
- c.save();
- c.translate(center.x, center.y); /*平移变换*/
- /*绘制刻度*/
- function drawScale(){
- c.moveTo(radius - scale, 0);
- c.lineTo(radius, 0);
- };
- c.beginPath();
- c.arc(0, 0, radius, 0, 2*Math.PI, true);
- c.closePath();
- for (var i = 1; i <= 12; i++) {
- drawScale();
- c.rotate(hourangle); /*旋转变换*/
- };
- /*绘制时间(3,6,9,12)*/
- c.font = " bold 30px impack"
- c.fillText("3", 110, 10);
- c.fillText("6", -7, 120);
- c.fillText("9", -120, 10);
- c.fillText("12", -16, -100);
- c.stroke();
- c.restore();
- };
- /*绘制时针(h: 当前时（24小时制）)*/
- this.drawHourHand = function(h){
- h = h === 0? 24: h;
- c.save();
- c.translate(center.x, center.y);
- c.rotate(3/2*Math.PI);
- c.rotate(h*hourangle);
- c.beginPath();
- c.moveTo(0, 0);
- c.lineTo(hourHandLength, 0);
- c.stroke();
- c.restore();
- };
- /*绘制分针（m: 当前分）*/
- this.drawMinHand = function(m){
- m = m === 0? 60: m;
- c.save();
- c.translate(center.x, center.y);
- c.rotate(3/2*Math.PI);
- c.rotate(m*minangle);
- c.beginPath();
- c.moveTo(0, 0);
- c.lineTo(minHandLength, 0);
- c.stroke();
- c.restore();
- };
- /*绘制秒针（s：当前秒）*/
- this.drawSecHand = function(s){
- s = s === 0? 60: s;
- c.save();
- c.translate(center.x, center.y);
- c.rotate(3/2*Math.PI);
- c.rotate(s*minangle);
- c.beginPath();
- c.moveTo(0, 0);
- c.lineTo(secHandLength, 0);
- c.stroke();
- c.restore();
- };
- /*依据本机时间绘制时钟*/
- this.drawClock = function(){
- var me = this;
- function draw(){
- var date = new Date();
- Canvas.clearCxt();
- drawBackGround();
- drawCenter();
- me.drawHourHand(date.getHours() + date.getMinutes()/60);
- me.drawMinHand(date.getMinutes() + date.getSeconds()/60);
- me.drawSecHand(date.getSeconds());
- }
- draw();
- setInterval(draw, 1000);
- };
- };
- var main = function(){
- var clock = new Canvas.Clock();
- clock.drawClock();
- };
代码中涉及到了一些简单的canvas元素API 大家google一下即可，祝大家学习愉快:-D
来源：51CTO
