canvas教程

Canvas + JS 实现简易的时钟

字号+ 作者:H5之家 来源:H5之家 2016-01-21 10:03 我要评论( )

本文是对Canvas + JS 实现简易的时钟的讲解,对学习JavaScript编程技术有所帮助,与大家分享。

[摘要]本文是对Canvas + JS 实现简易的时钟的讲解,对学习JavaScript编程技术有所帮助,与大家分享。

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" 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

 

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