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鐘。時鐘本身並不復雜，也沒有使用圖片進行美化，不過麻雀雖小五髒俱全，下面就與大家分享一下：
演示效果：
html代碼：
復制代碼 代碼如下:
<!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:
復制代碼 代碼如下:
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);
};
/*時鐘*/
Canvas.Clock = function(){
var me = Canvas,
c = me.cxt,
radius = 150, /*半徑*/
scale = 20, /*刻度長度*/
minangle = (1/30)*Math.PI, /*一分鐘的弧度*/
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鐘*/
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 大家度娘一下即可
以上就是本文的全部內容了，希望對大家學習canvas能夠有所幫助。