之前學習了下html5中的canvas元素，為了練練手就實現了一個簡易的時鍾。時鍾本身並不復雜，也沒有使用圖片進行美化，不過麻雀雖小五臟俱全，下面就與大家分享一下：
- 實現效果：
- html代碼：
<!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代碼:
var Canvas = {}; Canvas.cxt = document.getElementById('canvasId').getContext('2d'); Canvas.Point = function(x, y){ this.x = x; this.y = y; }; /*擦除canvas上的所有圖形*/ Canvas.clearCxt = function(){ var me = this; var canvas = me.cxt.canvas; me.cxt.clearRect(0,0, canvas.offsetWidth, canvas.offsetHeight); }; /*時鍾*/ Canvas.Clock = function(){ var me = Canvas, c = me.cxt, radius = 150, /*半徑*/ scale = 20, /*刻度長度*/ minangle = (1/30)*Math.PI, /*一分鍾的弧度*/ hourangle = (1/6)*Math.PI, /*一小時的弧度*/ hourHandLength = radius/2, /*時針長度*/ minHandLength = radius/3*2, /*分針長度*/ secHandLength = radius/10*9, /*秒針長度*/ center = new me.Point(c.canvas.width/2, c.canvas.height/2); /*圓心*/ /*繪制圓心（表盤中心）*/ 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(); }; /*通過坐標變換繪制表盤*/ function drawBackGround(){ c.save(); c.translate(center.x, center.y); /*平移變換*/ /*繪制刻度*/ 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); /*旋轉變換*/ }; /*繪制時間(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(); }; /*繪制時針(h: 當前時（24小時制）)*/ 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(); }; /*繪制分針（m: 當前分）*/ 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(); }; /*繪制秒針（s：當前秒）*/ 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(); }; /*依據本機時間繪制時鍾*/ 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(); };
代碼中涉及到了一些簡單的canvas元素API 大家google一下即可，祝大家學習愉快:-D